Дисертації з теми "Transitional channel flow"
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Vanyaza, Sydwell Luvo. "Non-newtonian open-channel flow : effect of shape on laminar and transitional flow." Thesis, Cape Technikon, 2004. http://hdl.handle.net/20.500.11838/874.
Повний текст джерелаWhen designing the open channels to transport the homogenous non-Newtonian slurries, the effect of channel shape is one of the parameters that should be checked and very little research has been conducted to address this matter. Open channels are commonly applied in the mining industry where mine tailings have to be transported to the disposal dams at high concentrations to save water consumption. This thesis addresses the effect of the cross-sectional shape of the channel with emphasis on laminar and transitional flow of non-Newtonian fluids. The literature review on the flow of Newtonian and non-Newtonian fluids has been presented. The most relevant one to this topic is the work done by Straub et al (1958) for Newtonian fluids and the analytical work presented by Kozicki and Tiu (1967) for non-Newtonian fluids. Authors like Coussot (1994) and Haldenwang (2003) referred to their work but did not comprehensively verified it experimentally. Three flume shapes were designed to investigate this problem namely, rectangular, semi circular, and trapezoidal flume shape. The test rig consisted of a 10 m long by 300mm wide tilting flume that can be partitioned into two sections to form a 150 mm wide channel. All three flume shapes were tested in both the 150 mm and 300 mm wide flumes. This flume is linked to the in-line tube viscometer with three tube diameters namely, 13 mm; 28 mm; and 80 mm. The experimental investigation covered a wide range of flow rates (0.1-45l/s), and flume slopes (1-5 degrees). The fluids tested were kaolin suspension (5.4 - 9% v/v), CMC solution (1 - 4% m/m), and bentonite suspension (4.6 and 6.2% mlm). The models found in the literature were evaluated with the large database compiled from the test results to predict the laminar and transitional flow of these fluids with the aim of checking the effect of the cross-sectional shape of these channels selected in these flow regimes. For all the flume shapes and non-Newtonian fluids selected in this thesis it was found that in predicting the laminar flow, the effect of shape is adequately accounted for by the use of hydraulic radius. In predicting the transitional flow, it was found that the effect of shape does not have to be included.
Hagan, J. "Nonlinear instabilities and transition to turbulence in magnetohydrodynamic channel flow." Thesis, Coventry University, 2013. http://curve.coventry.ac.uk/open/items/cc5976b0-419c-4944-a2ff-3af446a03d05/1.
Повний текст джерелаKabwe, Christine Mahemba Wa. "Transitional flow of non-newtonian fluids in open channels of different shapes." Thesis, Cape Peninsula University of Technology, 2015. http://hdl.handle.net/20.500.11838/924.
Повний текст джерелаOpen channels are widely used in the mining industries where homogeneous non-Newtonian slurries have to be transported around plants (Sanders et al., 2002). As water becomes scarcer and more costly due to legislative limitations, higher concentrations of slurries have to be transported. Very little work had been done to predict the laminar-turbulent transition flow of non-Newtonian fluids in open-channels. The effect of open channel on flow of non-Newtonian fluids in the transition region is not well understood. A systematic study on the effect of open channel shape on transitional flow for different non-Newtonian fluids has as far as can be ascertained not been conducted to date. This work investigated the effect of the channel cross-sectional shape on transitional flow of non-Newtonian fluids. There are a number of analytical and empirical methods available for the prediction of transitional flow in open channels. However, there are no conclusive guidelines in the literature that would predict the transitional flow for different shapes. A large experimental database for non-Newtonian flow produced by the Flow Process Research Centre at the Cape Peninsula University of Technology in rectangular, trapezoidal, semi-circular and triangular channels at slopes varying from 1° to 5° was used to achieve the objective. The test fluids consisted of bentonite and kaolin clay suspensions, and solutions of carboxymethyl cellulose (CMC) of various concentrations. The shear stress - shear rate behaviour of each test fluid was measured using in-line tube viscometry. To evaluate predictive models of transitional flow in various channel shapes, a comparison of critical actual velocities with models velocities was conducted for power law, Bingham plastic and yield-shear thinning fluids. After comparison of various models in different flume shapes, Haldenwang‟s critical Reynolds number for rectangular channels was deemed to be the best predictive model. To improve Haldenwang‟s critical Reynolds number, new correlations based on Haldenwang‟s (2003) method were developed for each shape studied and their corresponding critical velocities were compared. By combining all the transition data for the four shapes a new correlation “combined model” was developed for onset of transition and onset of full turbulence which can adequately accommodate the four different channel shapes for all fluids tested.
Klinkenberg, Joy. "Stability analysis of channel flow laden with small particles." Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-42271.
Повний текст джерелаQC 20111013
Patrick, Wilfred Vinod. "Computations of Flow Structures and Heat Transfer in a Dimpled Channel at Low to Moderate Reynolds Number." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33415.
Повний текст джерелаMaster of Science
Vujisić, Ljubomir B. (Ljubomir Branislav). "Heat transfer at transition to turbulence in channel flows with eddy promoters." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36499.
Повний текст джерелаCoumes, Thomas M. "Effects of 1 Hz imposed bulk flow unsteadiness on laminar/turbulent transition in a straight channel." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27012.
Повний текст джерелаGreco, Francis J. "Effects of 2 Hz imposed bulk flow unsteadiness on laminar/turbulent transition in a straight channel." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27013.
Повний текст джерелаHögberg, Markus. "Optimal Control of Boundary Layer Transition." Doctoral thesis, KTH, Mechanics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3245.
Повний текст джерелаOsman, Sohaib Mustafa Mohammed. "Experimental investigation into convective heat transfer in the transition flow regime by using nanofluids in a rectangular channel." Thesis, University of Pretoria, 2019. http://hdl.handle.net/2263/77873.
Повний текст джерелаThesis (PhD (Mechanics))--University of Pretoria, 2019.
Mechanical and Aeronautical Engineering
PhD (Mechanics)
Unrestricted
Vamvakoulas, Christos. "Advanced computational modelling and simulation of transition to turbulence in separated suddenly-expanded channel flows." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/6827.
Повний текст джерелаAcharya, Neelavara Shreyas. "Numerical study of transition to turbulence in plane Poiseuille flow in physical space and state space." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS019/document.
Повний текст джерелаThis thesis numerically investigates the dynamics of turbulence in plane Poiseuille flow driven by a fixed pressure gradient. The focus is especially on computations carried out within the minimal flow unit (M.F.U.). In the first part, turbulent simulations are carried out in spatially periodic channels. In the M.F.U. simulations, the turbulent activity appears to be localised near one wall and the long term dynamics features abrupt reversals. In the next part, we look numerically for exact coherent states in the M.F.U. system. Edge states, which are computed using bisection exhibit streamwise vortices and a single pair of streaks localised near only wall at all times. Different state space representations and phase portraits were constructed using appropriately chosen variables. The dynamics along a turbulent reversal is organised around transient visits to a subspace of (almost) symmetric flow fields. A nearly-symmetric exact travelling wave (TW) solution was found in this subspace. Stability analysis of the TW revealed that its unstable eigenvectors separate the state space into two symmetric basins. In the last part of this thesis, the self-similarity of the different non-trivial equilibrium flow regimes computed in this work, is addressed. Contrarily to most studies focusing on symmetric solutions, the present study suggests that inner scaling is relevant for the description of edge regimes as well although the self-similarity is not as satisfactory as for the turbulent regimes
Koth, Howard Edwin. "Effects of 1, 2, 3 and 4 Hz imposed bulk flow oscillations on transition in a straight channel with 40 to 1 aspect ratio." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237988.
Повний текст джерелаThesis Advisor(s): Ligrani, Phillip M. ; Subramanian, Chelakara S. "June 1990." Description based on signature page. DTIC Identifier(s): Channel flow, Tollmien Schlichting waves, Klebanoff type waves, Stroubal number, Turbulence. Author(s) subject terms: Imposed oscillations, Tollmien-Schlichting waves, Klebanoff type waves, phase-averaged velocity, longitudinal velocity fluctuations, intermittency, center mode of secondary instability. Includes bibliographical references (p. 219-222). Also available online.
Naqvi, Syed Ali Asjad, and Stockhammer Engelbert. "Directed Technological Change in a post-Keynesian Ecological Macromodel." WU Vienna University of Economics and Business, 2017. http://epub.wu.ac.at/5809/1/SFC_DTC_WP_version.pdf.
Повний текст джерелаSeries: Ecological Economic Papers
Searle, Toby William. "Purely elastic shear flow instabilities : linear stability, coherent states and direct numerical simulations." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28991.
Повний текст джерелаDupuis, Victor. "Étude expérimentale d’écoulements soumis à une transition longitudinale de rugosité en lit simple et en lit composé." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1154/document.
Повний текст джерелаThis PhD thesis investigates the effect of a longitudinal change in floodplain land use on an overflooding river flow. We consider a transition between a meadow and a woodland and vice versa. This change in land use is associated with a change in hydraulic roughness, between a bed roughness (highly submerged meadow) and emergent macro-roughnesses (trees), respectively modelled by a plastic artificial grass and an array of emergent cylinders. The flows are experimentally investigated in an 18 m x 3 m laboratory flume. In a first step, we investigate the flow through a cylinder array in a single channel, focusing on the effect of bed roughness on the cylinder wakes and on the seiche phenomenon (strong free surface oscillations). In a second step, we study the development towards flow uniformity of compound channel flows with a uniform hydraulic roughness on the floodplains. The asymmetrical growth of the compound channel mixing layer, the self-similarity property and the three-dimensional organisation of the turbulent coherent structures associated with the mixing layer are analysed. In a third step, we investigate the longitudinal change in roughness in compound channel configuration, which effects on mixing layer and on coherent structures are discussed. We also assess the contributions to lateral transfers of momentum between main channel and floodplain by turbulent diffusion, by mass exchange and by secondary currents
Zou, Ziqiang. "A sharp interface method for low Mach two-phase flows with phase change Toward asymptotic-preserving low-Mach correction for sharp interface two-phase flows with capillary effects An Accurate Sharp Interface Method for Two-Phase Compressible Flows at Low-Mach Regime." Thesis, université Paris-Saclay, 2020. https://tel.archives-ouvertes.fr/tel-03178310.
Повний текст джерелаA sharp interface approach is presented for computing two-phase flows with surface tension and phase change in low Mach regime. To develop such a model, where slight compressible effects are taken into account as well as correct thermodynamical closures, both the liquid and the gas are considered compressible and described by a precise compressible solver. This compressible solver adopt a splitting technique called "acoustic-transport splitting" which splits the Euler system into two parts: acoustic and transport. Based on the acoustic subsystem, an approximate Riemann solver that accounts for surface tension and phase change effects is developed. The interface between two-phase flows is captured by the Level Set method that is considered to be sharp. The interface capturing issue of the Level Set method within the Eulerian framework is the key point of the two-phase flow simulations, and in this work we propose and adopt high-order approaches for interface advection, redistancing and curvature estimation. In low Mach regime, conventional compressible solvers lose accuracy and a low Mach correction is then necessary to reduce the numerical dissipation. For a sharp interface method, the interface is treated as the shock-wave contact discontinuity via the Ghost Fluid method. Without a smooth region at the interface, such discontinuity existing at the interface presents a huge challenge to the design of a numerical scheme. The well-known low Mach fix in literature could lead to significant truncation error, especially for two-phase flows with large density and sound speed ratios. To recover a good asymptotic-preserving property, we propose a new low Mach correction with rigorous asymptotic analysis. Several numerical test cases have been employed to validate the present numerical approach and enlighten its good performance
Guo, Longkai. "Numerical investigation of Taylor bubble and development of phase change model." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI095.
Повний текст джерелаThe motion of a nitrogen Taylor bubble in glycerol-water mixed solutions rising through different types of expansions and contractions is investigated by a numerical approach. The CFD procedure is based on an open-source solver Basilisk, which adopts the volume-of-fluid (VOF) method to capture the gas-liquid interface. The results of sudden expansions/contractions are compared with experimental results. The results show that the simulations are in good agreement with experiments. The bubble velocity increases in sudden expansions and decreases in sudden contractions. The bubble break-up pattern is observed in sudden expansions with large expansion ratios, and a bubble blocking pattern is found in sudden contractions with small contraction ratios. In addition, the wall shear stress, the liquid film thickness, and pressure in the simulations are studied to understand the hydrodynamics of the Taylor bubble rising through expansions/contractions. The transient process of the Taylor bubble passing through sudden expansion/contraction is further analyzed for three different singularities: gradual, parabolic convex and parabolic concave. A unique feature in parabolic concave contraction is that the Taylor bubble passes through the contraction even for small contraction ratios. Moreover, a phase change model is developed in the Basilisk solver. In order to use the existed geometric VOF method in Basilisk, a general two-step geometric VOF method is implemented. Mass flux is calculated not in the interfacial cells but transferred to the neighboring cells around the interface. The saturated temperature boundary condition is imposed at the interface by a ghost cell method. The phase change model is validated by droplet evaporation with a constant mass transfer rate, the one-dimensional Stefan problem, the sucking interface problem, and a planar film boiling case. The results show good agreement with analytical solutions or correlations
Louchart, Arnaud. "Dynamique spatio-temporelle des communautés phytoplanctoniques côtières et de leurs caractéristiques intrinsèques, à partir d'une approche automatisée à haute résolution Phytoplankton distribution from Western to Central English Channel, revealed by automated flow cytometry during the summer-fall transition Spatial niches of phytoplankton functional groups assessed during a spring bloom development in two temperate coastal seas Untangling the vertical distribution of phytoplankton groups along a salinity gradient through the Baltic Sea and the Skagerrak-Kattegat straits." Thesis, Littoral, 2020. http://www.theses.fr/2020DUNK0556.
Повний текст джерелаIn coastal ecosystems, phytoplankton composition, distribution and dynamics are strongly influenced by spatial and temporal variations of hydrological structures and biogeochemical parameters, consequences of natural and anthropogenic pressures. Reference monitoring, due to its low spatial and temporal resolution, may fail to detect key events as the initiation and end of phytoplankton outbursts or harmful algal blooms (HABs). By increasing the spatial and/or temporal resolution as well as completing taxonomical counting by investigating the phytoplankton whole size spectra, the use of automated sensors may allow contributing to a better understanding of the distribution and dynamics of this major player in biogeochemichal cycles, at the basis of most foof webs. This thesis consists in studying the characteristics of phytoplankton functional groups defined from their optical properties at the single-cell level, in relation to spatio-temporal variability encountered in contrasting marginal seas, applying the pulse shape-recording automated flow cytometry. This functional classification reflects the diversity of particles according to morphological and physiological properties. First of all, the distribution of phytoplankton groups and their traits where explored in the Western and Central English Channel during the summer period. Most groups formed patches of abundance and biomass near the Ushant front and were structured at the sub-mesoscale. Secondly, phytoplankton functional groups dynamics was characterized in the Eastern English Channel and Southern North Sea during the development period of diatoms and Phaeocystis globosa spring groups, by calculating LCBD and SCBD, wich allowed the observation of spatial segregation between phytoplankton groups. Their distribution was explained by the niche parameters (marginality and tolerance). Finally, the vertical distribution of phytoplankton functional groups in a salinity gradient was addressed in the Baltic Sea, in relation to the biogeochemical properties of the water masses and the characteristics of each PFGs. The variations of the traits are thus stand out as the best predictors of the horizontal and vertical distribution of phytoplankton groups with the respect to niche parameters and spatial descriptors (dispersion, physical and biological parameters). The functional approach, derived from phytoplankton optical properties addressed by automated flow cytometry, coupled to the niche analysis, make it possible to better explain and predict community responses to environmental gradients, such responses being detected in parallel by diversity indices. This work benefited from the support of local (MARCO State-Region Plan Contract), national (CNRS-MTES convention) and international European H2020 JERICO-NEXT projects
Raghuram, S. "An Experimental Investigation of Transitional and Turbulent Channel Flow." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5904.
Повний текст джерелаHaque, AKM Enamul. "Some characteristics of open channel transition flow." Thesis, 2009. http://spectrum.library.concordia.ca/976403/1/MR63268.pdf.
Повний текст джерелаTENG, WEI-HSIEN, and 鄧慰先. "Numerical simulations of rapidly varied flow in open channel transitions." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/19548388579322004405.
Повний текст джерелаKumar, Arun. "Velocity Coefficient in a Open Channel Flow with Gradual Transition." Thesis, 2017. http://ethesis.nitrkl.ac.in/8776/1/2017_MT_A_Kumar.pdf.
Повний текст джерелаSiedband, Marc A. "A flow visualization study of laminar/turbulent transition in a curved channel." Thesis, 1987. http://hdl.handle.net/10945/22269.
Повний текст джерелаSrinivas, S. S. "Turbulence in Soft Walled Micro Channels." Thesis, 2016. http://etd.iisc.ac.in/handle/2005/2877.
Повний текст джерелаSrinivas, S. S. "Turbulence in Soft Walled Micro Channels." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2877.
Повний текст джерелаAhmadzadegan, Amir. "Molecular Simulation of Chemically Reacting Flows Inside Micro/Nano-channels." Thesis, 2013. http://hdl.handle.net/10012/7937.
Повний текст джерелаUlerich, Rhys David. "Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles." Thesis, 2014. http://hdl.handle.net/2152/26886.
Повний текст джерелаtext