Dissertations / Theses on the topic 'Hydrodynamics and hydraulic engineering'
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Mulahasan, Saad. "Hydrodynamics of large-scale roughness in open channels." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/95099/.
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This thesis investigates the hydrodynamics of flow around/and or above an obstacle(s) placed in a fully turbulent developed flow such as flow around lateral bridge constriction, flow over bridge deck and flow over square ribs that are characterized with free surface flow. Also this thesis examines the flow around one-line circular cylinders placed at centre in a single open channel and floodplain edge in a compound, open channel. *Hydrodynamics studies of compound channels with vegetated floodplain have been carried out by a number studies of authors in the last three decades. To enrich our understanding of the flow resistance, comprehensive experiments are carried out with two vegetation configurations-wholly vegetated floodplain and one-line vegetation and then compared to smooth unvegetated compound channel. The main result of the flow characteristics in vegetated compound channels is that spanwise velocity profiles exhibit markedly different characters in the one-line and wholly-vegetated configurations. Moreover, flow resistance estimation results are in agreement with other experimental studies. *A complementary experimental study was carried out to investigate the water surface response in an open-channel flow through a lateral channel constriction and a bridge opening with overtopping. The flow through the bridge openings is characterized by very strong variation of the water surface including undular hydraulic jumps. The results of simulation that was carried by (Kara et al. 2014, 2015) showed a reasonable agreement between measured and computed water surface profiles for the constriction case and a fairly good was achieved for the overtopping case. *Evaluation of the shear layer dynamics in compound channel flows is carried out using infrared thermography technique with two vegetation configurations - wholly vegetated floodplain and one-line vegetation in comparison to non-vegetated floodplains. This technique also manifests some potential as a flow visualization technique, and leaves space for future studies and research. Results highlight that the mixing shear layer at the interface between the main channel and the floodplain is well captured and quantified by this novel approach. iii *Flume experiments of turbulent open channel flows over bed-mounted square bars at low and intermediate submergence are carried out for six cases. Two bar spacings, corresponding to transitional and k-type roughness, and three flow rates, are investigated. This experimental study focused on two of the most aspects of channel rough shallow flows: water surface profile and mean streamwise vertical velocity. Results show that the water surface was observed to be very complex and turbulent for the large spacing cases, and comprised a single hydraulic jump between the bars. The streamwise position of the jump varied between the cases, with the distance of the jump from the previous upstream bar increasing with flow rate. The free surface was observed to be less complex in the small spacing cases, particularly for the two higher flow rates, in which case the flow resembled a classic skimming flow. The Darcy-Weisbach friction factor was calculated for all six cases from a simple momentum balance, and it was shown that for a given flow rate the larger bar spacing produces higher resistance. The result of the simulation that was carried out by Chua et al. (2016) shows good agreement with the experiments in terms of mean free surface position and mean streamwise velocity. *Drag coefficient empirical equations are predicted by a number of authors for an array of vegetation. The research aims to assess the suitability of various empirical formulations to predict the drag coefficient of in-line vegetation. Drag coefficient results show that varying the diameter of the rigid emergent vegetation affects significantly flow resistance. Good agreement is generally observed with those empirical equations. Key Words: Flow Visualization; Infrared Thermography; Shallow Flows; Shear layer; Image processing; Experiment; Free surface; Bridge hydrodynamics; Bridge overtopping; Vegetation roughness, Emergent vegetation, Drag coefficient, blockage; Compound channel, Lateral velocity profiles; Hydraulic resistance; Hydraulic jump, Square bars.
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Tatlock, Benjamin. "A hybrid finite-volume finite-difference rotational Boussinesq-type model of surf-zone hydrodynamics." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30443/.
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An investigation into the numerical and physical behaviour of a hybrid finite-volume finite-difference Boussinesq-type model, using a rotational surface roller approach in the surf-zone is presented. The relevant theory for the required development of a numerical model implementing this technique is outlined. The proposed method looks to achieve a more physically realistic description of the hydrodynamics by considering the rotational nature of the highly turbulent flow found during wave breaking. This involves a semi-analytical solution to the vorticity transport equation and provides a mechanism by which energy is dissipated. Resolving vorticity within the flow also allows vertical profiles of the horizontal velocity to be constructed, offering valuable detail that is otherwise unavailable when using equivalent irrotational Boussinesq-type models. By obtaining additional information about the structure of the flow, other quantities can be determined, such as the undertow, which has a key role in morphodynamic processes occurring in this region. These benefits are combined with a finite-volume finite-difference scheme, which yields improvements in stability and possesses inherent shock-capturing capabilities. The ability of the model to replicate laboratory observations is verified, and identified shortcomings are explained in the context of the numerical procedure and the assumptions made during the derivation of the governing equations. Although the weak nonlinearity of the Boussinesq-type equations means the shoaling characteristics of the model do not accurately reflect those found experimentally, the adopted formulation of the finite-volume scheme is shown to prevent the inclusion of the necessary higher-order derivatives which exist in a fully-nonlinear formulation. In order to establish a realistic dissipation mechanism, it is vital that the extent of any misleading numerical artefacts are recognised and their effects alleviated. This study explores a range of physical attributes predicted by the present model and discusses the numerical features of the scheme, evaluating how these influence the results.
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Friedrichs, Carl T. "Hydrodynamics and morphodynamics of shallow tidal channels and intertidal flates /." Woods Hole, Mass. : Woods Hole Oceanographic Institution, 1993. http://hdl.handle.net/1912/1176.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, 1993."Doctoral dissertation." "February 1993." At head of title: Woods Hole Oceanographic Institution, Massachusetts Institute of Technology. Includes bibliographical references (p. 205-214).
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Thein, Myint. "Experimental investigation of flow resistance and velocity distributions in a rectangular channel with large bed-roughness elements." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19580.
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Lu, Zhihua. "Stochastic modelling of unsteady open channel flow and reliability analysis /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20LU.
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Amini, Sina. "Hydrodynamics and Salinity of Pontchartrain Estuary During Hurricanes." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1845.
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A hurricane is a combination of sustained winds, low atmospheric pressures and precipitation. Over the past decades, Louisiana has experienced several devastating hurricanes.
The east bank of the City of New Orleans is bounded by Lake Pontchartrain to the North and the Mississippi River to the South. Lake Pontchartrain is a brackish system connected to the Gulf of Mexico through Lake Borgne to the East. As a Hurricane enters the Estuary from the Gulf of Mexico, it imposes a sustained surge of a few meters which may lead to flooding in areas which are not protected by levees. These flood water may be saline.
Saltwater flooding is an environmental issue in flooded marshlands since saltwater can be fatal to some plants. The response of salinity and storm surge to hurricane duration which represents the forward speed of the storm is numerically modeled.
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Khodier, Mohanad A. "Weir-Baffled Culvert Hydrodynamics Evaluation for Fish Passage Using Particle Image Velocimetry and Computational Fluid Dynamic Techniques." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3078.
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Due to a recent increase in environmental awareness regarding fish passage through hydraulic constructions including culverts, an evaluation for the passage of wild brown trout through a weir-baffled prototype-scale culvert was performed under a variety of culvert slopes and discharge conditions. The influence of the sample fish population and the length of the individual fish on passage rates were investigated; the data showed that the brown trout fish passage sample size evaluated in this study (25 per test) was sufficiently large to minimize sample size dependency. Fish behavior while traversing the culvert was observed and reported, including resting/staging zone locations.
Turbulent flow through weir baffled-culvert was also simulated numerically using three-dimensional numerical model employing the (k- �) model, Renormalized Group k-� model (RNG), and Large Eddy Simulation (LES) model. Experimental data measured with the Particle Image Velocimetry (PIV) were used to assess the accuracy and the applicability of these turbulence models in predicting the turbulent flow characteristics of the flow through a weir-baffled culvert at different spatial locations inside the culvert for variety of culvert slopes and flow rates. The influence of flow rates and culvert slopes on the forward velocities and reverse velocities was evaluated. It was noted that the influence of the flow rates on the flow velocities depends on the culvert slopes. Turbulent kinetic energy and flow direction effects on flow characteristic were also evaluated. Validation of Manning’s equation and Manning’s roughness coefficient for the tested culvert were reported.
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Yeow, Kervin. "Three dimensional scour along offshore pipelines." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0008.
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Three-dimensional scour propagation along offshore pipelines is a major reason to pipeline failures in an offshore environment. Although the research on scour in both numerical and experimental aspect has been extensive over the last three decades, the focus of the investigation has been limited to the two-dimensional aspect. The knowledge on three-dimensional scour is still limited. This dissertation presents the results of an experimental investigation on threedimensional scour along offshore pipelines in (1) steady currents (2) waves only and (3) combined waves and current. The major emphasis of the investigation is to investigate the propagation of the scour hole along the pipeline after the initiation of scour. Physical experiments conducted were used to quantify the effects of various parameters on scour propagation velocities along the pipeline. The problem of monitoring real time scour below a pipeline was solved by using specifically developed conductivity scour probes. Effects of various parameters such as pipeline embedment depth, incoming flow Shields parameter, Keuglegan- Carpenter (KC) number and flow incident angle to the pipeline on scour propagation velocities along the pipeline were investigated. The investigations clearly reveal that scour propagation velocities generally increase with the increase of flow but decrease with the increase of the pipeline embedment depth. A general predictive formula for scour propagation velocities is proposed and validated against the experimental results. There are still some common issues related to pipeline scour that is lacking in the literature to date. One of these issues is the effects of Reynolds number on two-dimensional scour beneath pipelines. A numerical approach was adopted to investigate the Reynolds-number dependence of two-dimensional scour beneath offshore pipelines in steady currents. A novel wall function is proposed in calculating the suspended sediment transport rate in the model. The effects of Reynolds number were investigated by simulating the same undisturbed Shields parameters in both model and prototype but with different values of Reynolds number in two separate calculations. The results revealed that scour depths for prototype pipelines are about 10~15% smaller than those for model pipelines. The normalized time scales was found to be approximately the same, and the simulated scour profiles for the model pipelines agree well with the experimental results from an independent study. The backfilling of pipeline trenches is also an important issue to the design and management of offshore pipelines. A numerical model is developed to simulate the self-burial of a pipeline trench. Morphological evolutions of a pipeline trench under steady-current or oscillatory-flow conditions are simulated with/without a pipeline inside the trench. The two-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the standard k-e turbulence closure, as well as the sediment transport equations, are solved using finite difference method in a curvilinear coordinate system. Different time-marching schemes are employed for the morphological computation under unidirectional and oscillatory conditions. It is found that vortex motions within the trench play an important role in the trench development.
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Venugopal, Vengatesan. "Hydrodynamic force coefficients for rectangular cylinders in waves and currents." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/6351/.
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The research into hydrodynamic loading on ocean structures is concentrated mostly on circular cross section members and relatively limited work has been carried out on wave loading on rectangular sections, particularly in waves and currents. This research work is therefore carried out focussing on the evaluation of hydrodynamic force coefficients for sharp edged rectangular cylinders of various cross-sections (aspect ratios), subjected to waves and currents. Three cylinders with three different cross-sections are constructed and tested vertically, as surface piercing and horizontally, as fully submerged with the cylinder axis parallel to the wave crests. The aspect ratios considered for this investigation are 1.0, 112, 2/1, 3/4 and 4/3. The length of each cylinder is 2000mm. The sectional loadings are measured on a 100mm section, which is located at the mid-length of the cylinder. The forces are measured using a force measuring system, which consists of load cells, capable of measuring wave and current forces. The in-line & transverse forces (for vertical cylinders) and horizontal & vertical forces (for horizontal cylinders) have been measured. For horizontal cylinder, to study the effect of depth of variation on submergence of the cylinder, the tests are carried out for two depths of submergence. The experiments are carried out at the Hydrodynamic Laboratory, Department of Naval Architecture and Ocean Engineering, University of Glasgow. The tests are carried out in a water depth of 2.2m with regular and random waves for low Keulegan-Carpenter (KC) number up to 4.5 and the Reynolds number varied from 6.397xl03 to 1.18xl05 • The combined wave and current effect has been produced by towing the cylinders in regular waves, along and opposite to the wave direction at speeds of ± 0.1 mis, ± 0.2 mls and ± 0.3 mls. Based on Morison's equation, the relationship between inertia and drag coefficients are evaluated and are presented as a function of KC number for various values of frequency parameter, {3. For the vertical cylinders, the drag coefficients decrease and inertia coefficients increase with increase in KC number up to the range of KC tested for all the cylinders. For the horizontally submerged cylinders, the drag coefficients showed a similar trend to vertical cylinders, whereas the inertia coefficients decrease with increase in KC number for all the cylinders. This reduction in inertia force is attributed to the presence of a circulating flow [Chaplin (1984)] around the cylinders. The random wave results are consistent with regular wave results and the measured and computed force spectrum compares quite well. While computing the force coefficients in the case of combined waves and currents, only the wave particle velocity is used, as the inclusion of current velocity tends to produce unreliable drag force coefficients. For vertical cylinders, the drag and the inertia coefficients in combined waves and currents are lower than the drag and the inertia coefficients obtained in waves alone. For horizontal cylinders the drag coefficients are larger than those obtained for waves alone and the inertia coefficients are smaller than those measured in waves alone. The Morison's equation with computed drag and inertia coefficients has been found to predict the measured forces well for smaller KC numbers. However, the comparison between measured and computed positive peak forces indicate that the computed forces are underestimated. It is suggested that if the wave particle kinematics are directly measured, this discrepancy between measured and computed forces might well be reduced. Wave excitation forces are also reported in non-dimensional forms in the diffraction regime, using 3D-Green function method. Wave induced pressure distribution around the cylinder in regular waves have been measured and are reported as normalised pressures. Wave run-up on the cylinder surfaces has been measured and simple empirical formulae are presented for run-up calculations on the cylinder surfaces. The results of this investigation show that the cylinder aspect ratio plays major role on hydrodynamic force coefficients, dynamic pressure distribution and on wave run-up on cylinder surfaces.
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Cooper, Alison Jane. "The effects of rotation and wall compliance on hydrodynamic stability." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/109582/.
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The effects of system rotation and passive wall compliance on hydrodynamic stability is investigated. Rotating channel flow is studied where a Coriolis force instability mechanism produces streamwise rolls at modest Reynolds numbers and rotation rates. The linear stability of mean flow states consisting of a combination of plane Poiseuille and Couette flows is considered using spectral Chebyshev collocation with a staggered grid. A Newton algorithm is implemented in three-dimensional parameter space to calculate minimum points of the neutral surfaces. Weakly nonlinear behaviour of the rolls is studied using a Ginzburg-Landau formulation and accurate numerical values for the equation coefficients indicate supercritical instability. Effects of external pressure gradient and three-dimensionality on boundary layer stability over compliant walls is examined. In these cases an inflexion point in the boundary layer profile promotes a powerful inviscid instability mechanism. Two-dimensional profiles, including a Falkner-Skan representation, are considered in inviscid and viscous analyses with plate-spring and viscoelastic compliant wall models. Walls which are rendered stable with respect to hydroelastic instabilities are shown to reduce maximum spatial growth rates by up to 60%. This work is extended to consider the three-dimensional boundary layer over a rotating disc where inviscid (Type 1) and viscous (Type 2) instabilities can coexist. A single layer viscoelastic wall model coupled to a sixth order system of fluid equations, which accounts for Coriolis and streamline curvature effects, is solved by a spectral Chebyshev tau technique. The Type 1 stationary instability is found to be significantly stabilised, whilst the effect on the Type 2 mode is complex but can be destabilising. For travelling-wave modes, across a band of positive frequencies, evidence of modal coalescence between the Type 1 and 2 instabilities leading to absolute instability is presented. This would constitute a major route to transition and appears to be caused by large values of viscous stress work at the wall/flow interface.
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Wells, Jared Lawrence. "Effect of angular orientation on the hydrodynamic forces acting on a body in a restricted waterway." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/41572.
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A slender body theory method developed for a body moving parallel to a wall in shallow water is extended to include angular orientation of the body to the wall. The method satisfies only the zero normal velocity condition on the external boundaries but does not take into account the effect of induced flows on the body itself. A spheroid and a Series 60, block .80 hull were the bodies studied. The side force and yaw moment on each body were determined numerically for varying angular orientation with respect to either a single wall or canal bank. For both cases results for a range of depths and wall separation distances are presented. It is found that the method gives good qualitative side force predictions for a body moving parallel to a wall, but is unable to correctly predict the yaw moment or the side force due to angular orientation. This result dictates the need for a more complex mathematical model to properly represent the flow than the simple model and quasiâ steady method used here.
Master of Science
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Ou, Zhiliang. "Numerical simulation of flow around vertical cylinders." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0185.
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Local scour around bridge piers can cause serious damages and structural failure to the bridge. Correct prediction of the scour is an important criterion for the engineering design. Though the subject has been investigated for many decades, the theoretical developments have been very limited due to the complicated interaction of three-dimensional flow and the sediment transport. This thesis concerns the flow around a vertical bottom mounted cylinder exposed to currents and is considered as the initial phase of a study towards modeling local scour around vertical bottom-mounted structures. The aim of the present study is to obtain a better understanding of the complex three-dimensional flow and the mechanisms related to the scouring. The study started with the development of a three-dimensional numerical model to simulate flow around cylindrical structures. After validation of the model, the model was applied to investigate flow around an isolated rectangular cylinder. Unsteady flows around cylinders of a square cross section (A/D = 1) and a rectangular cross section (A/D = 2) were simulated to understand the flow properties around a cylinder other than a circular cross section. Three-dimensional flow patterns, pressure distribution, forces on the cylinder and vortex-shedding frequencies were discussed. It was found that the present numerical results generally agree well with the experimental data. Flow around a vertical cylinder mounted on a rigid bed was then investigated by the numerical model. A circular and a square cross sections were considered respectively. Flow structures of horseshoe vortex and the wake vortex which are the major mechanisms leading to the scouring around the base of the vertical cylinder were explored. The bed shear stress distributions that directly affect the scour processes were discussed. Finally the numerical model was applied to study the flow around a submerged square cylinder mounted on a bed, which has significant engineering relevance to the local scour around structures, such as bridge pier foundation itself, or a caisson placed underwater around the pier bottom for scour protection. The numerical calculations were carried out at different cylinder heights to investigate the effect of the cylinder height on the flow properties. It was found that for submerged cylinders with the height of less than one and a half of the cylinder side width the maximum bed shear stress amplification is about 60% of the value of an infinite long cylinder. The quantification of the shear stress reduction is important for scour protection design.
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Chan, Hoi Sang. "A three-dimensional technique for predicting first-and second-order hydrodynamic forces on a marine vehicle advancing in waves." Thesis, University of Glasgow, 1990. http://theses.gla.ac.uk/1490/.
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This thesis presents theoretical formulations and numerical computations for predicting first- and second-order hydrodynamic forces on a marine vehicle advancing in waves. The theoretical formulation starts with the derivation of the governing equations for the boundary-value problem of potential flow and its consequence leads to linearised radiation and diffraction problems using the peturbation expansion technique. Solutions of these two problems are obtained by solving the three-dimensional Green function integral equations over the mean wetted body surface. The forward speed free surface Green function representing a translating pulsating source potential for infinite water depth and finite water depth is derived using double Fourier transformation technique. This source potential reduces to an oscillating source at zero speed or to a Kelvin source at zero frequency. In order to solve the three-dimensional Green function integral equations efficiently, symmetry properties of the Green function and the body surface are exploited in the numerical implementation. Using a fully submerged ellipsoid and a half-submerged ellipsoid as examples, the free surface and forward speed effects on hydrodynamic coefficients are investigated. Their cross coupled hydrodynamic coefficients calculated by the present theory satisfy with Timman-Newman relationships. Numerical results for the first-order hydrodynamic coefficients, the wave excitation loads and the resulting motion responses of surface ships are presented. For zero speed case excellent correlations between the calculated and experimental results are found. For the forward speed case, the three-dimensional translating pulsating source modelling and three-dimensional oscillating source modelling with simple speed corrections on the linearised body boundary condition for pitch and yaw motions are used for a realistic ship. When the calculated results are compared with available experimental data, the three-dimensional translating pulsating source, modelling gives better correlations than the three-dimensional oscillating source modelling. Based on the first-order solutions, the mean second-order forces and moments are obtained by direct integrating second-order pressures over the mean wetted body surface. Using zero speed horizontal drifting forces and mean yaw moment as examples, the predictions of the mean second-order forces and moments are compared with available experimental results and found good agreement. For forward speed case the numerical computations for the added resistances of surface ships in head waves are performed by the three-dimensional translating pulsating source modelling and three-dimensional oscillating source modelling. The performance of the former is much better than the latter in comparison with available experimental results. It is found that the successful prediction of the peak of the added resistance is critically dependent upon the motion response results, especially in pitch. Effects of ship heading, forward speed, water depth on the first-order and second-order hydrodynamic forces are investigated.
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Shi, Jie. "Integrated modelling of hydrological and hydrodynamic processes, dynamic bacteria decay with climate change and intensive farming in riverine and estuarine water." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/98617/.
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The water quality deteriorations in river and estuarine waters are a global issue. Particularly, the water quality impairment due to contamination of Faecal Bacteria Indicator, such as E. coli and Faecal Coliform in river channel, estuary bathing and shellfish waters are of special interests due to potential risks to human health. These indicators are important in water quality assessment outlined in both EU Water Framework Directive and US Clear Water Act. The hypothesis of the study is that the global climate change and intensive farming would cause severe deterioration to faecal coliform levels in these water bodies. Approaches to quantify these impacts are carried out with numerically modelling through catchment model Soil and Water Assessment Tool (SWAT) and hydrodynamic model DIVAST with the focus in the coastal catchment of river Frome and Piddle connected to a natural harbour in Dorset, southern England.
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Evans, Paul Stephen. "Hydrodynamic characteristics of macrotidal straits and implications for tidal stream turbine deployment." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/70531/.
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National efforts to reduce energy dependency on fossil fuels have prompted examination of macrotidal nearshore zones around the UK for potential tidal stream resource development. Although a number of prospective tidal energy sites have been identified, the local hydrodynamics of these sites are often poorly understood. Tidal-energy developers rely on detailed characterisation of tidal energy sites prior to device field trials and installation. Although first-order appraisals may make macrotidal tidal straits appear attractive for development, detailed, site-specific hydrodynamic and bathymetric surveys are important for determining site suitability for tidal stream turbine (TST) installation. Understanding the ways in which coastal features affect tidal velocities at potential TST development sites will improve identification and analysis of physical constraints on tidal-energy development. Ramsey Sound (Pembrokeshire, Wales, UK) will soon host Wales’ first TST demonstration project. However, the local hydrodynamics of the sound have been underexamined. Ramsey Sound experiences a marked tidal asymmetry, with local bathymetric features that affect flow fields which are spatially heterogeneous in three dimensions. Using Ramsey Sound as a case study, this thesis has three objectives: (1) to examine the wake created by submerged objects through field- and laboratory-based measurements, (2) to experimentally investigate the effect of submergence on wake development and decay downstream of a conical island, and (3) to develop a TST suitability tool, which examines the effects of velocity, water depth and bed slope on power availability within a macrotidal coastal area. Laboratory experiments have shown that submergence level is an important parameter controlling wake structure and extent, and that changes in submergence level affect both the 3-D flow structure in the near wake and the 2-D far wake of islands. Analysis of physical and hydrodynamic characteristics in Ramsey Sound, including tidal velocities across the swept area of the pilot TST, vertical shear in the stream flow, estimated power output, water depth and bed slope, suggests that the spatial and temporal variability in the flow field may render much of Ramsey Sound unsuitable for tidal power extraction. Although the resource potential depends on velocity and bathymetric conditions that are fundamentally local, many prospective tidal energy sites are subject to similar physical and hydrodynamic constraints. Results of this study can help inform site selection in these complicated, highly dynamic macrotidal environments.
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Mancilla, Alarcón Cristhian A. "Hydrodynamic loadings and responses of a floating guardwall a fluid-structure interaction problem /." Master's thesis, Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/content/templates/?a=72.
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Teran, Gonzalez Grecia A. "3-D Hydrodynamic and Non-Cohesive Sediment Transport Modeling in the Lower Mississippi River." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1837.
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The purpose of this research is to develop a 3-D numerical model on the Lower Mississippi River to simulate hydrodynamics and non-cohesive sediment transport. The study reach extends from Bonnet Carré Spillway (RM 127) to Head of Passes (RM 0). Delft3D with sigma coordinates was selected as the river modeling tool. This model River domain is characterized by a complex distributary system that connects the Mississippi River to the Gulf of Mexico. The boundary conditions were: water levels in the Gulf and Head of Passes; and discharges upstream. For the calibration, there are observed data for both types of boundary conditions. Several periods of high discharge were simulated to compare water level, discharge, velocity profiles and sediment transport with measurements and accomplish calibration and validation of the model. A calibrated 3-D model has been developed with the following %RMSE: 5% for stage; 6% for discharge; and 5% for sand load.
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Gurung, Tshering T. "One-Dimensional Dynamic Modeling of the Lower Mississippi River." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1804.
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The Mississippi River (MR) has been engineered with the development of the levee system, dams for flood control measures, jetties, revetments and dredging of the navigation channel. These alterations have reduced the replenishment of the sediment to the Louisiana Coastal area. To aid in the restoration planning, 1-D numerical models have been calibrated and validated to predict the river response to various changes such as channel modifications, varied flow conditions and hurricane situations. This study utilized the HEC-RAS 4.1 and the CHARIMA (Dr. Forrest Holly, University of Iowa). The models were calibrated for hydrodynamics and sediment using Tarbert Landing discharges (HEC-RAS), Belle Chasse sand concentrations (CHARIMA), and Gulf of Mexico (GOM) stages. The models showed that a large percentage of the river flow is lost over the East Bank downstream of Bohemia which reduces the sand transport capacity of the river. This reach is subject to flow reversals during hurricanes.
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Girtz, Anne Marie. "Hydraulic and Hydrodynamic Stormwater Model for the Västanfors Area of the Municipality of Fagersta, Sweden: Climate Change Impacts and Future Stormwater Management." Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210711.
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Global temperatures and frequency of extreme weather events have increased over the last decade, with 2015 globally the warmest year on record. Future climate models are consistent with this trend, predicting larger year-to-year variations in precipitation, more precipitation in larger single events, and more frequent extreme events. Changes in weather phenomena due to climate change will impact the infrastructure in cities and therefore the vulnerability of society. Today’s urban stormwater systems are closely related to local hydrological characteristics, with systems designed to accommodate specific ranges of rainfall based on historical data. An increase in rainfall or extreme weather events may result in capacity problems for these systems and in turn, negative impacts to people and the environment. Stormwater management in Sweden is guided by municipal plans and country-wide design standards. Within these documents there is information on who is responsible and what standards must be met, but there is a lack of specific requirements on how to undertake these tasks. Recently, Svenskt Vatten has started to recognize the need for a more defined stormwater management methodology, and commissioned a study titled ‘Guidelines for the modelling of wastewater carrying systems and stormwater systems’. While larger municipalities have the resources to develop hydraulic models, smaller municipalities are often left out of this drive for proactive management. Often, there is no requirement for master planning initiatives, and more realistically, no budget to implement such initiatives. Thus, stormwater management is left to conventional methods and often undertaken on an as-needed basis, with minimal long-term planning. This thesis shows how a hydraulic computer model can serve as a simple, low-cost tool to assist municipalities – especially those of smaller size - in the sustainable planning and management of their stormwater systems. A case study was used to exemplify the objective, by demonstrating a proposed methodology that can be used to assess the impacts of climate change on urban infrastructure. This study was undertaken in collaboration with ÅF Infrastructure AB in Stockholm and the municipality of Fagersta, Sweden.Den globala temperaturen och frekvensen av extrema väderhändelser har ökat under de senaste tio åren, med 2015 globalt det varmaste året på posten. Framtida klimatmodeller är förenliga med denna trend, nederbörden förutsägs variera mer från år till år, mer nederbörd i större enskilda händelser, och mer frekventa extrema händelser. Förändringar i väderfenomen till följd av klimatförändringarna kommer att påverka infrastrukturen i städerna och därmed samhällets sårbarhet. Dagens urbana dagvattensystem är nära besläktade med lokala hydrologiska egenskaper, med system som syftar till att tillgodose specifika regn intervaller baserat på historiska data. En ökning av nederbörd eller extrema väderförhållanden kan leda till kapacitetsproblem för dessa system, och i sin tur negativa konsekvenser för människor och miljö. Dagvattenhantering i Sverige styrs av kommunala planer och landsomfattande normer för utformning. Inom dessa dokument finns information om vem som är ansvarig och vilka normer måste uppfyllas, men det finns en brist på särskilda krav på hur dessa uppgifter skall utföras. Nyligen har Svenskt Vatten börjat inse behovet av en mer definierad dagvattenhantering metodik, och beställt en undersökning med titeln "Riktlinjer för modellering av avloppsvatten bärsystem och dagvattensystem". Medan större kommuner har resurser att utveckla hydrauliska modeller, är mindre kommuner ofta utanför denna enhet för proaktiv hantering. Ofta finns det inget krav på initiativ huvudplanering, och mer realistiskt, att ingen budget avsätts för dessa initiativ. Således är dagvattenhantering kvar med konventionella metoder och genomförs endast vid behov, med minimal långsiktig planering. Denna avhandling visar hur en hydraulisk datormodell kan fungera som en enkel, låg kostnad verktyg för att hjälpa kommuner - särskilt de mindre storlek - i hållbar planering och förvaltning av sina dagvattensystem. En fallstudie användes för att exemplifiera målet, genom att visa en föreslagen metod som kan användas för att bedöma effekterna av klimatförändringarna på urban infrastruktur. Denna studie genomfördes i samarbete med ÅF Infrastruktur AB i Stockholm och kommunen Fagersta.
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Anderson, Brett Gordon. "Quantifying the interaction between riparian vegetation and flooding : from cross-section to catchment scale /." Connect to thesis, 2006. http://repository.unimelb.edu.au/10187/2086.
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This study investigates whether the flood regime in a catchment is sensitive to the condition of riparian vegetation along the river network. The research is based on a comprehensive assessment and synthesis of field and laboratory measurements of vegetation flow resistance. A new numerical model is developed to estimate the roughness characteristics of multi-species riparian assemblages at a cross-section. Reach-scale and catchment-scale flood routing models are then applied to estimate the impact of vegetation on flood characteristics at successively larger scales. The investigation reveals that when riparian vegetation is removed at catchment-scale, peak stage declines as channel capacity increases but is also increased as the upstream catchment responds more rapidly to rain. In fact, the two competing impacts tend to cancel out leaving flood peak stage relatively insensitive to riparian condition. However, the overbank duration of a flood and flow speeds (including wave celerity) were both found to be sensitive to vegetation condition; respectively increasing and decreasing with density of vegetation. The first stage of this research examines the magnitude of the vegetation contribution to overall channel roughness, and established a means to predict it. The features of the flow resistance generated by six plant types (mature trees; grasses; aquatic plants; flexible saplings; and large woody debris) were distilled from a comprehensive review of over 160 existing publications (Chapter 2).
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Gerber, George. "Unsteady pipe-flow using the Petrov-Galerkin finite element method." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50214.
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Thesis (MScEng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: Presented here is an Eulerian scheme for solving the unsteady pipe-flow equations. It is called the Characteristic Dissipative Petrov-Galerkin finite element algorithm. It is based on Hicks and Steffler's open-channel finite element algorithm [5]. The algorithm features a highly selective dissipative interface, which damps out spurious oscillations in the pressure field while leaving the rest of the field almost unaffected. The dissipative interface is obtained through upwinding of the test shape functions, which is controlled by the characteristic directions of the flow field at a node. The algorithm can be applied to variable grids, since the dissipative interface is locally controlled. The algorithm was applied to waterhammer problems, which included reservoir, deadend, valve and pump boundary conditions. Satisfactory results were obtained using a simple one-dimensional element with linear shape functions.
AFRIKAANSE OPSOMMING: 'n Euleriese skema word hier beskryf om die onbestendige pypvloei differensiaal vergelykings op te los. Dit word die Karakteristieke Dissiperende Petrov-Galerkin eindige element algoritme genoem. Die algoritme is gebaseer op Hicks en Steffler se oop-kanaal eindige element algoritme [5]. In hierdie algoritme word onrealistiese ossilasies in die drukveld selektief gedissipeer, sonder om die res van die veld te beinvloed. Die dissiperende koppelvlak word verkry deur stroomop weegfunksies, wat beheer word deur die karakteristieke rigtings in die vloeiveld, by 'n node. Die algoritme kan dus gebruik word op veranderbare roosters, omdat die dissiperende koppelvlak lokaal beheer word. Die algoritme was toegepas op waterslag probleme waarvan die grenskondisies reservoirs, entpunte, kleppe en pompe ingesluit het. Bevredigende resultate was verkry vir hierdie probleme, al was die geimplementeerde element een-dimensioneel met lineere vormfunksies.
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Shao, Zhiyu S. "TWO-DIMENSIONAL HYDRODYNAMIC MODELING OF TWO-PHASE FLOW FOR UNDERSTANDING GEYSER PHENOMENA IN URBAN STORMWATER SYSTEM." UKnowledge, 2013. http://uknowledge.uky.edu/ce_etds/5.
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During intense rain events a stormwater system can fill rapidly and undergo a transition from open channel flow to pressurized flow. This transition can create large discrete pockets of trapped air in the system. These pockets are pressurized in the horizontal reaches of the system and then are released through vertical vents. In extreme cases, the transition and release of air pockets can create a geyser feature.
The current models are inadequate for simulating mixed flows with complicated air-water interactions, such as geysers. Additionally, the simulation of air escaping in the vertical dropshaft is greatly simplified, or completely ignored, in the existing models.
In this work a two-phase numerical model solving the Navier-Stokes equations is developed to investigate the key factors that form geysers. A projection method is used to solve the Navier-Stokes Equation. An advanced two-phase flow model, Volume of Fluid (VOF), is implemented in the Navier-Stokes solver to capture and advance the interface.
This model has been validated with standard two-phase flow test problems that involve significant interface topology changes, air entrainment and violent free surface motion. The results demonstrate the capability of handling complicated two-phase interactions. The numerical results are compared with experimental data and theoretical solutions. The comparisons consistently show satisfactory performance of the model.
The model is applied to a real stormwater system and accurately simulates the pressurization process in a horizontal channel. The two-phase model is applied to simulate air pockets rising and release motion in a vertical riser. The numerical model demonstrates the dominant factors that contribute to geyser formation, including air pocket size, pressurization of main pipe and surcharged state in the vertical riser. It captures the key dynamics of two-phase flow in the vertical riser, consistent with experimental results, suggesting that the code has an excellent potential of extending its use to practical applications.
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Stafne, Brice E. "Development and application of a two-dimensional hydrodynamic model for assessment of modern and historical flow conditions of Upper Mississippi River Pool 8 near La Crosse, Wisconsin." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3537.
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The Upper Mississippi River System (UMRS) is a diverse and dynamic ecosystem that includes the main stem river channel, side channels, backwater floodplains and lakes, islands, wetlands, grasslands, and floodplain forests. The hydrology of this rich ecosystem is one of the key drivers for physical, chemical and biological processes. However, the hydrology and hydraulics of the UMRS has been drastically altered from its natural state as a result of the construction of the locks and dams in the 1930s. Beginning with the Water Resources Development Act of 1986, biologists, ecologists, and engineers have been working to restore the river to a more natural state within the current constraints imposed by the lock and dam system. In an effort to restore rivers to a more natural state, the determination of a hydraulic reference condition is essential to understanding the "why and how" of historical river system function. Understanding the fundamental processes of historical conditions will help prioritize resources and better quantify possible outcomes for riverine restoration.
The main goal of this study was to construct a hydrodynamic reference condition for Pool 8 of the Upper Mississippi River System using hydrodynamic computational fluid dynamic (CFD) modeling. The CFD model will provide a better understanding of pre-impoundment flow conditions as compared to post-impoundment conditions today. The numerical model was constructed and developed primarily from a pre-impoundment 1890s topographic map with bathymetric cross-sections in the channels. The 1890s map and other sources from the U.S. Army Corps of Engineers provided historic elevation and hydraulic reference data for model calibration. The calibrated historic model was then compared with a current model of similar scale representing post-impoundment conditions, allowing for quantitative analysis of the differences between the two conditions.
Model results indicated large changes in average depth and average velocity between historic and current conditions in certain parts of the pool, while others remained relatively unchanged. For example, velocities decreased in main channel aquatic areas in the lower part of Pool 8 from an average of 0.6 m/s (2.0 ft/s) under historic conditions to 0.1 m/s (0.3 ft/s) under current conditions. In the same part of the pool, however, velocities in contiguous backwater areas remained relatively constant, with most remaining less than 0.25 m/s (0.82 ft/s). Additionally, in the lower part of the pool, discharge distribution between the floodplain areas and the main channel was historically much more dynamic, with flow concentrated in the main and secondary channels at discharges less than 2265 m3/s and in the floodplains at greater than 2265 m3/s. Under current conditions, discharge distribution is much less dynamic, with approximately 2/3 of the total discharge conveyed on the floodplain for all discharges modeled (283 m3/s to 2832 m3/s or 10,000 ft3/s to 100,000 ft3/s).
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Driss, Slim. "Hydraulic design of culverts." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28377.
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Culverts are designed to carry water from one side of an embankment to another. There are many culverts under a typical highway and they add significantly to its cost. The hydraulic design of a culvert is surprisingly complex and since its primary purpose is to convey water, it is important that it has the full intended flow capacity. The objective of this thesis was to develop a computer program to help an engineer with the hydraulic design of culverts. The user of the program can choose between designing a new culvert or checking the adequacy of an existing culvert from a hydraulic, point of view. The program handles the problem of sediment deposition that can occur and reduce the capacity of culverts having gentle slopes. The most widely used culvert shapes are included in the program and in this thesis. Comments are provided on the conditions under which certain shapes are best. Culvert inlets are given, and some improved inlet designs are presented since the inlet design can have a major impact on the cost of the culvert. Also, erosion at the culvert outlet is discussed and suggestions are provided on how to prevent it or cope with it.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Smith, Heather Dianne. "Flow and sediment dynamics around three-dimensional structures in coastal environments." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196261689.
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Hodgkinson, Derek Anthony Martin. "Computer graphics applications in offshore hydrodynamics." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26705.
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The results of hydrodynamic analyses of two problems involving offshore structures are displayed graphically. This form of presentation of the results and the liberal use of colour have been found to significantly help the ease in which the results are interpreted.
For the transformation of waves around an artificial island, a time history of the evolution of the regular, unidirectional wave field around an artificial island is obtained. Through the use of colour, regions in which wave breaking occurs have been clearly defined. The numerical technique used is based on the finite element method using eight noded isoparametric elements. The determination of the transformed wave field takes wave breaking, wave refraction, diffraction, reflection and shoaling into account. The graphical display is achieved by using a plotting program developed for the output of finite element analyses.
The motions of a semi-submersible rig are computed from the RAO curves of the rig, used to obtain its' small response in a random sea. The numerical technique used in the analysis assumes that the vertical members are slender and may be analysed using the Morison equation whereas the hulls are treated as large members which are discretised and analysed using diffraction theory. The discretisation of the cylinders and hulls together with the time history of the rig's motions are displayed graphically. Once again, the graphical display is plotted using a program developed for the output of finite element analyses for four noded elements. In this case, a finite element technique has not been employed but the results were ordered to act as though this is the case. The slender members (cylinders) and large members (hulls) are clearly distinguishable by using different colours. The elements used in the analysis are also clearly shown.
The VAX 11/730 system was used to obtain the results shown. A video tape, using the results of a time stepping procedure, was made by successively recording the hardcopies produced by the VAX printer. The time stepping could also be seen, in real time, on the IRIS.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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McKillip, Michael Lee. "Coupling the Hydrodynamic and Water Quality Model CE-QUAL-W2 With a Multi-Trophic Fish Bio-Energetics Model for Lake Roosevelt, Washington." PDXScholar, 2008. https://pdxscholar.library.pdx.edu/open_access_etds/3078.
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Grand Coulee Dam created Franklin D. Roosevelt Lake as part of the Columbia Basin Project. Located in northeastern Washington State, the Project provides economically important hydropower (19 billion kilowatt hours per year), irrigation (225,000 ha), flood control, and sport fishing ($5 to 20 million annually). A good system understanding aids in balancing these beneficial uses for the 230 km long reservoir. The reservoir's atypical 45-day mean residence time is much shorter than a typical lake, and much longer than for a riverine dam. The spring freshet requires drawdowns of 15 to 20 m for flood control—the driving characteristic of reservoir operations.
A physically based two-dimensional hydrodynamic and water quality model, CE-QUAL-W2 Version 3.5 (Cole and Wells, 2006), is coupled with a fish bioenergetics model based on the Stockwell and Johnson model (1997, 1999) to examine the effects of hydrodynamics on the reservoir algae-zooplankton-kokanee food web. This model was applied and calibrated to Lake Roosevelt with model improvements of multiple zooplankton compartments and zooplankton omnivory. Calibration parameters included temperature, dissolved oxygen, nutrients, algae, and zooplankton. The fish bioenergetics model is applied over the entire reservoir model space to generate a spatial and temporal fish growth potential distribution. The fish model refinements include sub-daily time-steps and an optimized vertical foraging strategy.
The linked model suggests that kokanee fish growth potential is seasonally limited by both warm water and prey densities. While the lake ecology is significantly affected by the reservoir operations in general, the pelagic fish growth potential did not appear sensitive to minor changes in reservoir operations. However, the model suggests that the advantageous foraging locations shift seasonally and that optimal foraging strategies are dependent on fish size.
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Jonsson, Patrick. "Smoothed particle hydrodynamics in hydropower applications : modeling of hydraulic jumps." Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16867.
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In present thesis, the Lagrangian particle based method Smoothed ParticleHydrodynamics (SPH) is used to model two-dimensional problems associated with hydropower applications such as dam break evolution and hydraulic jumps. In the SPHmethod, the fluid domain is represented by a set of non-connected particles which possess individual material properties such as mass, density, velocity, position and pressure. Besides representing the problem domain and acting as information carriers the particles also act as the computational frame for the field function approximations. As the particles move with the fluid the material properties changes over time due to interaction with neighbouring particles. The adaptive nature of the SPH-method together with the nonconnectivity between the particles results in a method that is able to handle very large deformations as is the case for highly disordered free-surface flows such as hydraulic jumps.The dam break case was used as a model validation test case where the response of different parameter settings was explored. The SPH spatial resolution and the choice of artificial viscosity (a term in the momentum equation) constants had a major impact on the results. Increasing the spatial resolution increased the number of flow features resolved and setting the constants equal to unity resulted in a highly viscous and unphysical solution.Following the parameter study, the work focused on SPH simulations of hydraulic jumps. A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment. Several features of the jump were explored using the SPH method and good agreement with theory and experiments was obtained for e.g. the conjugate depth and the mean free surface elevation in the roller section. However, the free surface fluctuation frequencies were over predicted and the model could not capture the decay of fluctuations in the horizontal direction.Godkänd; 2013; 20130425 (patjon); Tillkännagivande licentiatseminarium 2013-05-29 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Patrick Jonsson Ämne: Strömningslära/Fluid Mechanics Uppsats: Smoothed Particle Hydrodynamics in Hydropower Applications Modelling of Hydraulic Jumps Examinator: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Doktor, forskare Gustaf Gustafsson, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 20 juni 2013 kl 09.00 Plats: E231, Luleå tekniska universitet
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Wu, Gangwei. "Drag reduction in large diameter hydraulic capsule pipeline /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9904874.
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Yang, Bo. "Elastohydrodynamic model of reciprocating hydraulic rod seals." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34747.
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Reciprocating rod seals are widely used in hydraulic systems to prevent the hydraulic fluid from leaking into and polluting the environment. In this research an elastohydrodynamic model of a generalized reciprocating hydraulic rod seal, including mixed lubrication and surface roughness, has been successfully developed. This model consists of coupled fluid mechanics, contact mechanics, thermal analysis and deformation analyses.
Such model is capable of predicting the key seal performance characteristics, especially net leakage and friction force. This allows evaluation of potential seal designs and serves as design tools. Also as this model has been developed, the basic physics of seal operation has been clarified, which stimulates the development of innovative seal concepts, such as seals with engineered sealing surfaces.
The results of this study indicate that in general, hydraulic rod seals operate in the mixed lubrication regime, although under certain conditions full film lubrication may occur over a portion of the sealing zone. The roughness of the seal surface and the rod speeds play important roles in determining whether or not a seal will leak. Cavitation during the outstroke and partial full film lubrication during the instroke tend to prevent net leakage. The behavior of a reciprocating hydraulic rod seal with a double lip or two seals in tandem arrangement can be very different from that of a similar seal with a single lip. For the double lip seal, the secondary lip can strongly affect the behavior of the primary lip by producing an elevated pressure in the interlip region. The same seal characteristics that promote effective sealing in a single lip seal and, in addition structural decoupling of multiple lips, are found to promote effective sealing in a multiple lip seal.
The model is validated through comparisons of model predictions with experimental measurements and observations by industry partners. The results have shown the predicted leakage and friction force for various seal and operation conditions are consistent with the measurements.
A seal with micro-pattern on the sealing surface also has been investigated. The results indicate that an elaborately designed pattern can improve the sealing characteristics of the seal, without significantly affecting the friction force.
In the end, the selection of the rod seal for a specific application using this analytical model is demonstrated. The best design can be picked up before a prototype being built.
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Tajima, Yoshimitsu 1972. "Surf zone hydrodynamics." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84236.
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Overby, Darryl Ray 1974. "Hydrodynamics of aqueous humor outflow." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89882.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 277-286).
Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness resulting from elevated intraocular pressure caused by a pathologic increase in the resistance to aqueous humor outflow from the eye. Currently, the physiological and ultrastructural bases for the generation of aqueous humor outflow resistance remain unclear in both the normal and glaucomatous eye, although experimental evidence suggests that the extracellular matrix within the juxtacanalicular connective tissue (JCT) is the principle resistive element. Johnson, Shapiro et al. (1992) have postulated that the resistance of the JCT is further increased by a hydrodynamic "funneling" interaction whereby the available area for aqueous flow through the JCT is reduced by the constraint that aqueous must cross the inner wall endothelium of Schlemm's canal through discrete pores. In this study, we focus on uncovering the role of the JCT in the generation of aqueous humor outflow resistance in the non-glaucomatous eye. Quick-freeze/deep-etch (QF/DE) electron microscopy was used to visualize the extracellular matrix within the JCT. A novel stereologic theory was developed to relate the two-dimensional void area and perimeter observed on a micrograph to the three-dimensional tissue porosity and specific surface, allowing the hydraulic resistance of an extracellular matrix to be estimated from a QF/DE micrograph. Extensive numerical studies were conducted to validate the predictions of the stereologic theory. To investigate the funneling effect,
(cont.) morphologic changes that would disrupt funneling were proposed and investigated to determine their role in the "washout" phenomenon (the progressive decrease in aqueous outflow resistance measured during experimental perfusion of non-human eyes). QF/DE revealed the presence of empty space devoid of extracellular matrix within the JCT. Washout was found to act through a reversible separation of the JCT from the basal lamina of the inner wall endothelium that was proposed to eliminate funneling. These results challenge the belief that aqueous outflow resistance is generated by extracellular matrix within the JCT. This study also suggests that the molecular components responsible for tethering the inner wall to the JCT are important regulators of aqueous humor outflow resistance in the normal eye and thereby represent potential targets for treatment of POAG.
by Darryl Ray Overby.
Ph.D.
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Sit, Arthur John. "Hydrodynamics of aqueous humour outflow." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11499.
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Elfving, Maria. "Hydraulic closed loop control." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-234932.
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The purpose of the thesis work is to investigate methods for closedloop control of hydraulic pressure in transmissions to make them bemore precise. This is desirable since it decreases the fuel consumptionas well as emissions, and improves the driving performance.To be able to study the behaviour of the transmission, a Simulink modelis designed with the parts relevant to the problem, and from this a linearmodel is obtained. Three different controllers are designed andimplemented in the Simulink model, to compare and analyze differentsolutions. The controllers implemented are a PI controller, a PIDcontroller and a LQR controller.The results from the simulation with the different controllers showstep responses to be able to evaluate their individual performance. Theresults show that all of the controllers meet the requirements for a stepreponse under better conditions, but under worse ones the LQR controllerperforms best of the three. The LQR controller is therefore themost suitable of the three controllers for this particular problem.Syftet med det här examensarbete är att undersöka olika metoder för återkopplad reglering av hydrauliskt tryck i en transmission för att göra det mer exakt. Detta är önskvärt eftersom det minskar bränsleåt- gången och utsläpp, och gör även körupplevelsen bättre. För att kunna studera transmission tas en Simulink-modell fram in- nehållande de delar som är relevanta för problemet, och från detta kan en linjär modell erhållas. Tre olika regulatorer tas fram och im- plementeras i Simulink-modellen, för att kunna jämföra och analysera de olika lösningarna. De regulatorer som tas fram är PI-regulator, PID- regulator och LQR-regualator. Resultaten från simuleringen med de olika regulatorerna visar stegs- var under varierande förutsättningar för att kunna utvärdera hur de presterar. Resultaten visar att alla regulatorer uppfyller kraven på ett stegsvar under bättre förhållanden, men LQR-regulatorn presterar bäst under svårare förhållanden. LQR-regulatorn är därför den mest relevanta reglerstrategin för det här problemet av de tre
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Jaipal, Prithviraj. "Hydraulic hybrids." Thesis, KTH, Fordonsdynamik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224159.
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Conventional IC Engine powertrain layouts in vehicles tend to consume considerable amounts of fuel and generate emissions that are harmful to the environment. Newer technologies have enabled the development of sustainable vehicle layout designs that favor a reduction in the exhaust emissions and energy consumption without compromising the vehicle’s performance. Hybrid vehicles and electric vehicles are the torch bearers for this development. Although electric vehicles feature high performance at lower emissions, they are generally limited by their range and high battery costs. Development of countries to equip for this electrification is another important factor here as with the development of more electric vehicles comes the problems associated with charging, like charging stations, charge scheduling (from power grid because of the high toll), etc. Hybrid electric vehicles are energy efficient and reduce the emissions considerably but their costs are substantially higher. Along with the higher efficiency generated by the electric machines, the possibility of regenerating braking energy reduces the energy consumption and increases the energy efficiency of the conventional layouts. Hydraulic hybrids in the recent years have gained recognition for their advantages and are known for being the cheaper alternative for hybridizing heavy vehicles. The ability of storing regenerative braking energy in this fluid form allows for higher cyclic efficiency when compared to that of the electrical means of storing energy. This thesis focuses on the design and modeling of the hydraulic hybrids using MATLAB/SIMULINK® to construct models depicting the use of the vehicles under the selected drive cycles. Regenerative braking has been one of prime focus for improving the range and minimising the energy consumption of the vehicle along with high operational efficiencies of the operating components. The thesis takes into account two cases, one with the case of a medium duty vehicle with a conventional IC Engine layout and the other with the case of electric forklifts. The two cases are compared with their hydraulic hybrid layouts along the lines of energy consumption, operational efficiencies and range. Through the design of these simulations, a comparative analysis of the hydraulic hybrid to the electric hybrid is provided for the case of the medium duty vehicle and the benefits of having an electric hydraulic hybrid layout designed for the electric forklift applications are studied.
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Zhang, Jing 1961. "System identification of bladder hydrodynamics." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26440.
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Understanding bladder mechanics and the changes caused by bladder outlet obstruction is an important task in urology. In this work, bladder mechanics are examined in terms of bladder hydrodynamics: the relation between a perturbing volume applied to the bladder and the evoked pressure change. A PC-based experimental system was built which can generate a computer-controlled perturbation volume and measure volume and pressure signals.The bladders of six minipigs, three normal and three obstructed, were subjected to stochastic volume perturbations about different average volume levels and evoked pressure changes were measured. The hydrodynamic stiffness transfer function relating volume and pressure was calculated and described by a second-order, lumped parametric model having inertial, viscous and elastic terms. Estimates of the elastic constant (K) increased linearly with volume in both normal and obstructed animals. The rate of increase was substantially greater in the obstructed animals than in the normals. Consequently, this approach shows promise for distinguishing normal and obstructed bladder mechanics.
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DePaoli, Laura L. (Laura Lynn) 1975. "Numerical modeling of wetland hydrodynamics." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80587.
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Geçer, Onur. "Shape optimization theory and applications in hydrodynamics." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33581.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 88-89).
The Lagrange multiplier theorem and optimal control theory are applied to a continuous shape optimization problem for reducing the wave resistance of a submerged body translating at a steady forward velocity well below a free surface. In the latter approach, when the constraint formed by the boundary conditions and the Laplace's governing equation is adjoined to the objective functional to construct the Lagrangian, the dependence of the state on the control is disconnected and they are treated as independent variables; whereas in the first approach, dependences are preserved for the application of Lagrange multiplier theorem. Both methods are observed to yield identical solutions and adjoint equations. Two alternative ways are considered for determining the variation of the objective functional with respect to the state variable which is required to solve the adjoint equation defined on the body boundary. Comparison of these two ways also revealed identical solutions. Finally, a free surface boundary is included in the optimization problem and its effect on the submerged body shape optimization problem is considered.
(cont.) Noting that the analytical solution to the local optimization problem holds for any initial body geometry, it is therefore concluded that the above study will provide theoretical background for an efficient hydrodynamic shape optimization module to be coupled with up-to-date flow solvers currently available such as SWAN.
by Onur Geçer.
S.M.
39
Donis, Peter Andrew. "Lattice gas hydrodynamics with Galilean invariance." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/44669.
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Wolfgang, Meldon J. (Meldon John) 1971. "Hydrodynamics of flexible-body swimming motions." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9546.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1999.Includes bibliographical references (p. 372-390).
The performance and agility of fish swimming motions have intrigued both biologists and fluid mechanicians for many years. Both have endeavored to understand the mechanics of fish swimming and to resolve the paradoxical observations surrounding the performance of fish, yet the unsteady hydrodynamics are not well-understood. In this thesis, the hydrodynamics of the fish-like swimming motions of a flexible body are examined through numerical simulation. Two- and three-dimensional boundary integral panel methods are developed which can model the steady straight-line swimming and unsteady maneuvering motions of a flexible-body of arbitrary thickness. Multiple, desingularized, infinitesimal wake sheet representation models the nonlinear dynamics of thin shear layer vorticity shed from an arbitrary number of predefined wake separation edges. The integrated performance quantities and the near-body unsteady flow features are corroborated through experimental comparisons. Employing this numeric scheme for a variety of fish forms, the unsteady flow dynamics are resolved in great detail and are found to be much more complex than that predicted by linear theory. In addition, fundamental mechanisms of near-body flow actuation, body-generated vorticity release, and wake vorticity control are found which allow the fish to generate thrust efficiently, to achieve outstanding performance, and to generate large, short-duration maneuvering forces. Specifically, the straight-line swimming motions of a flexible-body are studied through simulation of several fish geometries. Comparison to classical linear theory highlights the importance of the vortical dynamics in achieving performance and the complexity of the near-body flow patterns. The flow around the body is found to be highly longitudinal through systematic visualization of the body cross-sectional and waterline planes. A body-generated vortex ring structure, created through localized body undulations, actuates the smooth near-body longitudinal flow patterns around much of the fish body, resulting in strong vertical vorticity components bounding the wake thrust jet. Regions of high propulsive efficiency are identified for certain prescribed kinematics, and the performance is found to be strongly dependent on kinematic variation, recoil motions, and geometric modeling choices. Maneuvering hydrodynamics of fish swimming are studied through the simulation of a 60° "C" -turn of a Giant Dania. The formation and controlled release of body-generated vorticity through local contortions of the backbone is shown to affect the formation of a turning thrust jet for rapid maneuvering. The interaction body-generated free vorticity and regions of high fluid momentum with the sweeping motion of the tail fin is similarly shown to affect both the strength and direction of the turning jet. Through simulation of these straight-line swimming and unsteady maneuvering motions, fundamental mechanisms of vorticity control utilized by the fish are identified. Body-generated vorticity released by the body upstream is actuated by the motion of the oscillating tail fin, resulting in complex wake-wake-body interactions for varying kinematics. These interactions may enhance the performance by increasing thrust or increasing efficiency; similarly, large drag forces may be enhanced through constructive interaction of the wakes. Several novel vorticity control modes are elucidated for both straight-line steady swimming and unsteady maneuvering motions. Mechanisms of near-body flow actuation and vorticity control by the motions of swimming flexible-bodies and oscillating lifting surfaces may have tremendous potential for application to vehicle design and to unsteady maneuvering systems.
by Meldon John Wolfgang, IV.
Ph.D.
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Ward, Britton Reynolds. "The hydrodynamics of sailboat bailing devices." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41008.
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Hadjerioua, Boualem 1957. "Behavior of hydraulic jump basins." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/291709.
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The goal of this project was to determine the performance of two types of stilling basins with varying tailwater elevation. The performance was evaluated in terms of scour at the toe of the stilling basin and containment of the jump in the basin. The investigation involved establishing the relationships for different flow rates, different velocities and depth of approach flow for the U.S. Bureau of Reclamation stilling basins III and IV. It is well known that the Bureau of reclamation stilling basins perform satisfactorily for design tailwater conditions. It is not clear how much higher or lower the tailwater can be and still have marginally acceptable performance in the basin. This research sought to establish: (1) the behavior changes with high and low tailwater, and (2) the limiting range of tailwater for acceptable performance.
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Markonda, Raviteja, and Pratikchandra J. Vasava. "IMPROVED DESIGN FOR HYDRAULIC VALVE AND HYDRAULIC VALVE TESTING RIGIMPROVED DESIGN FOR HYDRAULIC VALVEAND HYDRAULIC VALVE TESTING RIG : DESIGN AND PRODUCT DEVELOPMENT." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-29534.
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The hydraulic testing rig is a machine that is used to test the hydraulic valves.The present testing rigs are used according to only some particular specification, but in ourproject we have developed a process and implemented the idea for building a UniversalHydraulic Testing Rig which can be able to test any kind of valves with simple adjustments.The hydraulic valves are mainly designed to carry out the flow of the hydraulic fluid with thedesired pressures. But it is observed that there are many pressure losses in the flow whichleads to the unreached flow pressures as expected. In a pre-project to this work a patentedhydraulic valve designed to improve the flow pressure of the hydraulic fluid. The main targetof the design of the valve is to decrease pressure losses and give maximum output from theother end of the valve. The Hydraulic Testing Rig is designed with the help of design softwareand flow simulation process helps to know about the pressure flow from inlet to outlet ofthe valve. After the testing of the design, the valve is tested on the new universal hydraulictest rig developed in this project. With the future use of the hydraulic valve test rig, thesimilarities and variations are observed from both the simulations done and test results canbe compared to optimize the valve design further. With the combination of hydraulic test rigand redesign hydraulic valve we will provide and experimental test rig possibility to bringthe better and maximum design that could be attained reducing the energy losses in hydraulicvalve designs.
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Brian, Harold Malcolm. "The hydrodynamics of single and multiple moonpools." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334552.
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Ismail, Ernesto Bram. "Smoothed particle hydrodynamics for nonlinear solid mechanics." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/11888.
Full textAbstract:
Includes abstract.Includes bibliographical references (leaves 115-117).
Smooth Particle Hydrodynamics (SPH) is one of the simplest meshless methods currently in use. The method has seen significant development and has been the germination point for many other meshless methods. The development of new meshless methods regularly uses standard SPH as a starting point, while trying to improve on issues related to consistency and stability. Despite these perceived flaws it is favoured by many researchers because of its simple structure and the ease with which it can be implemented.
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Koren, David W. "Column hydrodynamics of solvent in pulp processing." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5463.
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Bottom, Richard Glenn II. "On the hydrodynamics of ray-like swimming." Thesis, State University of New York at Buffalo, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1561510.
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Discovering the key-features of how aquatic swimmers such as stingrays propel themselves in nature can inspire the next generation of underwater vehicles with improved maneuverability and decreased noise signatures. To discover the key-features of stingrays swimming, fluid-structure interaction simulations of a self-propelled virtual stingray, modeled closely after the freshwater stingray, Potamotrygon orbignyi, are performed. The first closed-form kinematics description of the stingray's body motion was developed from three-dimensional experimental measurements of undulatory body motion of the fresh water stingray, Potamotrygon orbignyi, which is prescribed in our simulations. The self-propelled simulations produce a high-resolution view of the three-dimensional flow field and quantifiable forces created from the stingray's swimming unobtainable by other experimental means. A leading edge vortex (LEV) was discovered to be present on the pectoral disc of the stingray, which drastically affects the hydrodynamic forces and the pressure distribution on its disc. The LEV was found to stays attached to the stingray's body until its swimming cycle reverses direction at which time the vortex detaches to travels along with the stingray's swimming undulations, creating pressure differentials across the surfaces of the stingray which promotes thrust. At the time instance of highest thrust generation during its swimming cycle, three separate vortices present on the stingrays body, all of which were formed on the leading edge, are creating a pressure distribution promoting thrust. This finding can inspire new propulsive fins that generate LEV instead of mitigating separation.
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Imas, Leonard G. 1968. "Hydrodynamics involving a free-surface body juncture." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10095.
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Petelina, Nina. "Hydrodynamics of magnet-coil actuated robotic fish." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112550.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (page 44).
The hydrodynamics of two robotic fish were analyzed: a low cost toy robotic fish for developing live fish experimental techniques, HEXBUG(TM) Aquabot, and a low cost robotic fish for swarm robotics experiments, Scuba Fish. Both of these robotic fish use a magnet-coil actuation method in order to create caudal fin motion. A velocity imaging technique,, Particle Image Velocimetry (PIV), was used in order to characterize the wake structure created by the tail beat. Both robotic fish were towed through water as a high speed camera recorded the movement of seeding particles around the caudal fin, which are illuminated with a laser. From 2D PIV and 3D Synthetic Aperture PIV experiments for the Aquabots it has been identified that the discrete tail beat from the bang bang control creates vortex pairs at each start or stop motion of the caudal fin. Moreover, the wake structure from the shark Aquabot tail beat creates a wake structure similar to live dogfish sharks. Since the design of the Scuba Fish allowed more control over the motion of the tail, an additional ramp pwm caudal fin control was designed and tested in order to analyze the wake from a continuous tail beat. The results show that the vortex shedding pattern created by the pwm ramp design is different from the bang bang cases; the method creates a negative vortex ring with a small vortex pair at the end of the motion. This suggests that further designs of a continuous control have to be investigated in order to achieve a more real fish-like swimming behavior.
by Nina Petelina.
S.B.
50
Olaoye, Abiodun Timothy. "Hydrodynamics of unconventional SWATH vessels in waves." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100101.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 79-80).
The motion responses of unconventional Small Water-plane Area Twin Hull (SWATH) vessels are unique in the sense that viscosity has significant non-linear effects on their hydrodynamic parameters. The parametric optimization of the hull shape of these vessels to reduce the total resistance in waves yields an interesting hull form where viscous effects become significant and this kind of problem is generally more difficult to solve. This study aims to investigate the motion response of these special kind of ships in waves using both numerical and experimental approach with some theoretical simplifications to better understand the hydrodynamics of the ship. The two modes of motion of interest in this study are heave and pitch motions which were chosen in order to focus on the degrees of freedom which significantly contributes to the resistance of the ship in head waves. The vessel under investigation is an unmanned surface vessel (USV) proposed to be used to monitor a team of autonomous underwater vehicles. A scaled version of this model is built and some experiments were conducted at the MIT towing tank at zero speed. Additionally, the numerical methods are implemented using 2D and 3D potential flow solvers. As this is an ongoing project, the results obtained so far including the study of the effects of the inertial characteristics of the ship on the response amplitude operator (RAO) are presented.
by Abiodun Timothy Olaoye.
S.M.