Academic literature on the topic 'Nonlinear hydrodynamic analysis'
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Journal articles on the topic "Nonlinear hydrodynamic analysis"
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Léger, P., and S. S. Bhattacharjee. "Seismic fracture analysis of concrete gravity dams." Canadian Journal of Civil Engineering 22, no. 1 (February 1, 1995): 196–201. http://dx.doi.org/10.1139/l95-018.
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Nonlinear seismic analyses of a 90 m high concrete gravity dam, assumed to be located in eastern Canada, have been conducted using a smeared crack finite element model. Reduced frequency-independent added matrices have been used to represent the hydrodynamic and foundation interaction effects. Parametric analyses have been performed to assess the effects of the initial conditions induced by severe winter temperature, and the effects of hydrodynamic and foundation interaction mechanisms, on the nonlinear seismic behaviour of the dam. Key words: gravity dams, nonlinear seismic response, finite element, crack propagation.
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Viana, Carlos Alberto Alves, Diogo Stuani Alves, and Tiago Henrique Machado. "Linear and Nonlinear Performance Analysis of Hydrodynamic Journal Bearings with Different Geometries." Applied Sciences 12, no. 7 (March 22, 2022): 3215. http://dx.doi.org/10.3390/app12073215.
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In rotor dynamics, a traditional way of representing the dynamics of hydrodynamic bearings is using stiffness/damping coefficients. It is thus necessary to carry out a linearization of hydrodynamic forces around the shaft’s equilibrium position. However, hydrodynamic bearings have highly nonlinear nature, depending on operating conditions. Therefore, this paper discusses the applicability of these linear/nonlinear approaches using a computational model of the rotating system, where the finite element method is used for rotor modelling and the finite volume method for bearing calculation. The main goal is to investigate the boundaries for linear approximation of the hydrodynamic forces present in lobed hydrodynamic bearings, with the system operating under high loading conditions. Several numerical simulations were performed varying preload parameter and rotating speed. A comparison of the system’s responses, in time domain (shaft orbits) and frequency domain (full spectrum), is made for linear and nonlinear models. Results showed that trilobed bearings are more susceptible to nonlinearities, even in situations of smaller vibration amplitudes, while elliptical bearings are sensitive only under larger vibration amplitudes. These analyses are of great importance for mapping the influence of nonlinearities in different types of lobed hydrodynamic bearings with fixed geometry, varying the preload parameter to verify the influence on the system’s dynamic response. This study is important and serves as the basis for cases of monitoring and fault diagnosis (in the field of structural health monitoring) since it is crucial to distinguish what would be a fault signature or a standard nonlinear effect created by the use of hydrodynamic bearings.
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Shao, Song Shi, Jiong Sun, and Kai Liu. "Bifurcation Analysis for Sailing Stability of Autonomous Underwater Vehicle." Applied Mechanics and Materials 44-47 (December 2010): 1682–86. http://dx.doi.org/10.4028/www.scientific.net/amm.44-47.1682.
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There are several nonlinear elements in the equations of Autonomous Underwater Vehicle(AUV) movements. It is difficult to deal nonlinear problem with traditional methods. A hydrodynamic parameter interference is chosen as bifurcation parameter at first. Then the sailing stability of AUV with proportional-derivative controller is analysed by bifurcation theory. The center manifold theory is used to get the expression of system state parameters. And the Hopf bifurcation of system is analysed. The result is verified by numerical simulations. It shows that the hydrodynamic parameter’s changing will bring Hopf bifurcation for depthkeeping saiiling. And the range of hydrodynamic parameter value that insures AUV sailing stability is given.
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Deguchi, Kengo. "High-speed shear-driven dynamos. Part 1. Asymptotic analysis." Journal of Fluid Mechanics 868 (April 10, 2019): 176–211. http://dx.doi.org/10.1017/jfm.2019.178.
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Rational large Reynolds number matched asymptotic expansions of three-dimensional nonlinear magneto-hydrodynamic (MHD) states are the concern of this contribution. The nonlinear MHD states, assumed to be predominantly driven by a unidirectional shear, can be sustained without any linear instability of the base flow and hence are responsible for subcritical transition to turbulence. Two classes of nonlinear MHD states are found. The first class of nonlinear states emerged out of a nice combination of the purely hydrodynamic vortex/wave interaction theory by Hall & Smith (J. Fluid Mech., vol. 227, 1991, pp. 641–666) and the resonant absorption theories on Alfvén waves, developed in the solar physics community (e.g. Sakurai et al. Solar Phys., vol. 133, 1991, pp. 227–245; Goossens et al. Solar Phys., vol. 157, 1995, pp. 75–102). Similar to the hydrodynamic theory, the mechanism of the MHD states can be explained by the successive interaction of the roll, streak and wave fields, which are now defined both for the hydrodynamic and magnetic fields. The derivation of this ‘vortex/Alfvén wave interaction’ state is rather straightforward as the scalings for both of the hydrodynamic and magnetic fields are identical. It turns out that the leading-order magnetic field of the asymptotic states appears only when a small external magnetic field is present. However, it does not mean that purely shear-driven dynamos are not possible. In fact, the second class of ‘self-sustained shear-driven dynamo theory’ shows a magnetic generation that is slightly smaller in size in the absence of any external field. Despite its small size, the magnetic field causes the novel feedback mechanism in the velocity field through resonant absorption, wherein the magnetic wave becomes more strongly amplified than the hydrodynamic counterpart.
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Ghesmat, Karim. "In-Situ, Solvent-Assisted Gravity Drainage of Bitumen: Nonlinear Numerical Analysis." SPE Journal 19, no. 01 (June 17, 2013): 109–21. http://dx.doi.org/10.2118/165579-pa.
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Summary The use of condensing solvents, especially propane vapor, has been proposed for the low-temperature recovery of bitumen by gravity drainage. A full numerical analysis of such a process is presented. A hybrid spectral/finite-difference method was implemented to solve equations simultaneously. The results show that the hydrodynamics of a miscible front was highly dependent on the characteristics of the porous medium and also on the properties of the miscible fluid. As a significant factor, the dependency of the production flow rate on the thickness of the porous medium was measured. The order of dependency was found to be a function of time and cannot be considered as a constant. Hydrodynamic dispersion was also found to decrease this dependency. More-detailed results, along with quantitative analyses, are also discussed to indicate how the hydrodynamics was influenced by other porous-medium characteristics and fluid properties, such as dissolution rate and molecular diffusion.
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Bhattacharyya, S. K., and M. R. Haddara. "Parametric Identification for Nonlinear Ship Maneuvering." Journal of Ship Research 50, no. 03 (September 1, 2006): 197–207. http://dx.doi.org/10.5957/jsr.2006.50.3.197.
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A parametric identification method for the estimation of hydrodynamic derivatives embedded in the nonlinear steering equations for ship maneuvering in calm seas is presented. The models developed for identification involve determination of constant, "low-frequency" hydrodynamic derivatives. The method is robust, noniterative, and computationally light, and it requires no starting estimates. In this method, the time domain operations are converted to linear operations in the frequency domain. The responses of the ship in a few standard maneuvers have been simulated in the numerical examples, and the proposed method is applied to these data in order to estimate the hydrodynamic derivatives for a few "identifiable" combinations.
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Qiu Hai-Jian, Hu Yu-Lu, Hu Quan, Zhu Xiao-Fang, and Li Bin. "Nonlinear theory considering harmonic interaction using Eulerian hydrodynamic analysis." Acta Physica Sinica 67, no. 8 (2018): 088401. http://dx.doi.org/10.7498/aps.67.20180024.
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Deguchi, Kengo. "High-speed shear-driven dynamos. Part 2. Numerical analysis." Journal of Fluid Mechanics 876 (August 8, 2019): 830–58. http://dx.doi.org/10.1017/jfm.2019.560.
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This paper aims to numerically verify the large Reynolds number asymptotic theory of magneto-hydrodynamic (MHD) flows proposed in the companion paper Deguchi (J. Fluid Mech., vol. 868, 2019, pp. 176–211). To avoid any complexity associated with the chaotic nature of turbulence and flow geometry, nonlinear steady solutions of the viscous resistive MHD equations in plane Couette flow have been utilised. Two classes of nonlinear MHD states, which convert kinematic energy to magnetic energy effectively, have been determined. The first class of nonlinear states can be obtained when a small spanwise uniform magnetic field is applied to the known hydrodynamic solution branch of plane Couette flow. The nonlinear states are characterised by the hydrodynamic/magnetic roll–streak and the resonant layer at which strong vorticity and current sheets are observed. These flow features, and the induced strong streamwise magnetic field, are fully consistent with the vortex/Alfvén wave interaction theory proposed in the companion paper. When the spanwise uniform magnetic field is switched off, the solutions become purely hydrodynamic. However, the second class of ‘self-sustained shear-driven dynamos’ at the zero external magnetic field limit can be found by homotopy via the forced states subject to a spanwise uniform current field. The discovery of the dynamo states has motivated the corresponding large Reynolds number matched asymptotic analysis in the companion paper. Here, the reduced equations derived by the asymptotic theory have been solved numerically. The asymptotic solution provides remarkably good predictions for the finite Reynolds number dynamo solutions.
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Isaacson, Michael, and John Baldwin. "Moored structures in waves and currents." Canadian Journal of Civil Engineering 23, no. 2 (April 1, 1996): 418–30. http://dx.doi.org/10.1139/l96-046.
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The present paper provides a brief review of the analysis of moored floating structures in waves and currents. A hydrodynamic analysis is required in order to predict wave and current effects on floating structures, and corresponding numerical models for determining transmitted and reflected wave heights, added masses, damping coefficients, and wave exciting forces are summarized. A mooring analysis is required in conjunction with the hydrodynamic analysis in order to calculate the restraint provided by the mooring system, as well as the structure motions, mooring line and anchor loads, and mooring line configurations. Various aspects of static, dynamic, and nonlinear responses are discussed and illustrated with example applications. Key words: coastal engineering, currents, floating structures, hydrodynamics, mooring forces, ocean engineering, wave forces, waves.
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Pacuraru, Florin, Leonard Domnisoru, and Sandita Pacuraru. "On the Comparative Seakeeping Analysis of the Full Scale KCS by Several Hydrodynamic Approaches." Journal of Marine Science and Engineering 8, no. 12 (November 25, 2020): 962. http://dx.doi.org/10.3390/jmse8120962.
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The main transport channel of the global economy is represented by shipping. Engineers and hull designers are more preoccupied in ensuring fleet safety, the proper operation of the ships, and, more recently, compliance with International Maritime Organization (IMO) regulatory incentives. Considerable efforts have been devoted to in-depth understanding of the hydrodynamics mechanism and prediction of ship behavior in waves. Prediction of seakeeping performances with a certain degree of accuracy is a demanding task for naval architects and researchers. In this paper, a fully numerical approach of the seakeeping performance of a KRISO (Korea Research Institute of Ships and Ocean Engineering, Daejeon, South Korea) container ship (KCS) container vessel is presented. Several hydrodynamic methods have been employed in order to obtain accurate results of ship hydrodynamic response in regular waves. First, an in-house code DYN (Dynamic Ship Analysis, “Dunarea de Jos” University of Galati, Romania), based on linear strip theory (ST) was used. Then, a 3D fully nonlinear time-domain Boundary Element Method (BEM) was implemented, using the commercial code SHIPFLOW (FLOWTECH International AB, Gothenburg, Sweden). Finally, the commercial software NUMECA (NUMECA International, Brussels, Belgium) was used in order to solve the incompressible unsteady Reynolds-averaged Navier–Stokes equation (RANSE) flow at ship motions in head waves. The results obtained using these methods are represented and discussed, in order to establish a methodology for estimating the ship response in regular waves with accurate results and the sensitivity of hydrodynamical models.
Dissertations / Theses on the topic "Nonlinear hydrodynamic analysis"
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Bengana, Yacine. "Simulations numériques pour la prédiction de fréquences par champs moyens." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLET032.
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Les écoulements fluides jouent un rôle important dans de nombreux phénomènes naturels ainsi que dans de nombreux secteurs industriels. On s’intéresse dans cette thèse aux écoulements instationnaires oscillants provenant d’une bifurcation de Hopf.L’écoulement affleurant une cavité carrée ouverte présente deux cycles limites séparés par un état quasi-périodique instable. Nous avons décrit en détail ce scénario au moyen de simulations numériques directes, de l’analyse de stabilité linéaire et de l’analyse de Floquet. La bifurcation de Hopf dans la geometry de Taylor-Couette donne naissance à deux solutions, les spirals (ondes progressives) et les rubans (ondes stationnaires dans la direction axiale). Nous avons découvert que la branche des rubans est suivie de deux cycles hétéroclines consécutifs avec deux états axisymétriques comme point d’ancrage.L’analyse de stabilité linéaire autour des solutions stationnaires permet d’obtenir le seuil de bifurcation. Une autre approche, est la linéarisation autour du champ moyen. Cette approche permet d’obtenir des fréquences très proches des fréquences non linéaires et montre dans la plupart des cas un taux de croissance proche de zéro. Nous avons montré que les spirales, les rubans, la cavité entrainée ainsi que l’écoulement autour d’un objet prismatique vérifient cette propriété.Dans la convection thermosolutal, la linéarisation autour du champ moyen des ondes stationnaires ne permet pas d’obtenir les fréquences non linéaires et le taux de croissance est loin d’être zéro, par contre pour les ondes progressives cette propriété est pleinement satisfaite. Nous avons étudié la validité d’un modèle auto-cohérent dans le cas de ces ondes progressives. En effet, si l’écoulement vérifie la propriété du champ moyen, ce modèle est supposé calculer le champ moyen, la fréquence nonlinear ainsi que l’amplitude. Ce modèle est constitué de l’équation gouvernant le champ moyen couplé avec l’équation linéarisé au travers le mode le plus instable et des contraintes de Reynolds. Nous avons montré que dans le cas des ondes progressives ce modèle permet de prédire la fréquence non linéaire seulement très proche du seuil. La prédiction est améliorée significativement en considérant les ordres supérieurs dans le terme des contraintes de ReynoldsFluid flows play an important role in many natural phenomena as well as in many industrial applications. In this thesis, we are interested in oscillating flows origins from a Hopf bifurcation.The open shear-driven square cavity has two limit cycles separated by an unsteady quasi-periodic state. We have described this scenario in detail by using direct numerical simulations, linear stability analysis, and Floquet analysis. The Hopf bifurcation in Taylor-Couette flow gives rise to two solutions, spirals (traveling waves) and ribbons (standing waves in the axial direction). We discovered that the ribbons branch is followed by two consecutive heteroclinic cycles connecting two pairs of axisymmetric vortices. We studied in detail these two heteroclinic cycles.The linear stability analysis about the stationary solution is used to compute the threshold of the bifurcations. Another approach is the linearization about the mean field. This approach gives frequencies very close to that of the nonlinear system and shows in most cases a nearly zero growth rate. We have shown that spirals, ribbons, the lid-driven cavity and the flow around a prismatic object verify this property.In the thermosolutal convection, the frequencies obtained by the linearization about the mean field of the standing waves do not match the nonlinear frequencies and the growth rate is far from zero, on the other hand for the traveling waves this property is fully satisfied. We studied the validity of a self-consistent model in the case of the traveling waves. The self-consistent model consists of the mean field governing equation coupled with the linearized Navier-Stokes equation through the most unstable mode and the Reynolds stress term. This model calculates the mean field, the nonlinear frequency, and the amplitude without time integration. The self-consistent model is assumed to be valid for flows that satisfy the property of the mean field. We have shown that in this case, this model predicts the nonlinear frequency only very close to the threshold. We have improved significantly the predictions by considering higher orders in the Reynolds stress term
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Abdolmaleki, Kourosh. "Modelling of wave impact on offshore structures." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0055.
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[Truncated abstract] The hydrodynamics of wave impact on offshore structures is not well understood. Wave impacts often involve large deformations of water free-surface. Therefore, a wave impact problem is usually combined with a free-surface problem. The complexity is expanded when the body exposed to a wave impact is allowed to move. The nonlinear interactions between a moving body and fluid is a complicated process that has been a dilemma in the engineering design of offshore and coastal structures for a long time. This thesis used experimental and numerical means to develop further understanding of the wave impact problems as well as to create a numerical tool suitable for simulation of such problems. The study included the consideration of moving boundaries in order to include the coupled interactions of the body and fluid. The thesis is organized into two experimental and numerical parts. There is a lack of benchmarking experimental data for studying fluid-structure interactions with moving boundaries. In the experimental part of this research, novel experiments were, therefore, designed and performed that were useful for validation of the numerical developments. By considering a dynamical system with only one degree of freedom, the complexity of the experiments performed was minimal. The setup included a plate that was attached to the bottom of a flume via a hinge and tethered by two springs from the top one at each side. The experiments modelled fluid-structure interactions in three subsets. The first subset studied a highly nonlinear decay test, which resembled a harsh wave impact (or slam) incident. The second subset included waves overtopping on the vertically restrained plate. In the third subset, the plate was free to oscillate and was excited by the same waves. The wave overtopping the plate resembled the physics of the green water on fixed and moving structures. An analytical solution based on linear potential theory was provided for comparison with experimental results. ... In simulation of the nonlinear decay test, the SPH results captured the frequency variation in plate oscillations, which indicated that the radiation forces (added mass and damping forces) were calculated satisfactorily. In simulation of the nonlinear waves, the waves progressed in the flume similar to the physical experiments and the total energy of the system was conserved with an error of 0.025% of the total initial energy. The wave-plate interactions were successfully modelled by SPH. The simulations included wave run-up and shipping of water for fixed and oscillating plate cases. The effects of the plate oscillations on the flow regime are also discussed in detail. The combination of experimental and numerical investigation provided further understanding of wave impact problems. The novel design of the experiments extended the study to moving boundaries in small scale. The use of SPH eliminated the difficulties of dealing with free-surface problems so that the focus of study could be placed on the impact forces on fixed and moving bodies.
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Zhou, Zhengquan. "A theory and analysis of planing catamarans in calm and rough water." ScholarWorks@UNO, 2003. http://louisdl.louislibraries.org/u?/NOD,45.
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Thesis (Ph.D)--University of New Orleans, 2003.Title from electronic submission form. "A dissertation ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering and Applied Science"--Dissertation t.p. Vita. Includes bibliographical references.
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HUANG, JI-CHUAN, and 黃吉川. "Nonlinear hydrodynamic stability analysis of film flow." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/47545267465183822024.
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Sung, Hung-Ming, and 宋鴻明. "Nonlinear Hydrodynamic Stability Analysis of Non-Newtonian Liquid Film Flows." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/37739393960858511161.
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博士國立成功大學
機械工程學系碩博士班
92
This paper presents a stability analysis of thin viscoelastic and micropolar liquid films flowing down a plate or cylinder moving in a vertical direction. The nonlinear rupture problem of thin micropolar liquid films on a cylinder is also investigated. The long-wave perturbation method is employed to derive the generalized nonlinear kinematic equations for a free film interface. The current thin liquid film stability analysis provides a valuable input to investigations into the influence of the style of motion of the vertical plate or cylinder on the stability behavior of the thin film flow. The normal mode method is employed to solve the linear solutions of the film flow, and the threshold conditions and linear growth rate of the amplitudes are obtained to analyze the linear stability behavior. This study utilizes the multiple scales method and derives the corresponding Ginzburg-Landau equation to characterize the nonlinear behavior of the flow. The subcritical stability, subcritical instability, supercritical stability, and supercritical instability states are obtained from the nonlinear stability analysis. The present rupture analysis of a thin liquid film on a cylinder supports investigations into the onset of film rupture and permits an understanding of the relative influences of factors such as micropolar parameter, cylinder radius, van der Waals potential, and surface tension on the rupture process. The following conclusions can be drawn from the current numerical modeling results: (1)Influence of style of motion of vertical plate or cylinder on stability behavior of thin film flow: A downward direction motion of the vertical plate or cylinder tends to enhance the stability of the downward-traveling film flow on the plate or cylinder. The film flow system becomes more stable as the downward direction velocity of the plate or cylinder increases. The effects of the viscoelastic parameter, , and the micropolar parameter, , on the stability of the thin film flow are diminished as the downward direction velocity of the plate or cylinder increases. Conversely, an upward direction motion of the plate or cylinder tends to reduce the stability of the down-traveling film flow. The film flow system becomes more unstable as the upward direction velocity of the plate or cylinder increases. The effects of the viscoelastic parameter, , and the micropolar parameter, , on the stability of the thin film flow become more pronounced as the upward direction velocity of the plate or cylinder increases. (2)Influence of cylinder radius on stability behavior of thin film flow: The film flow becomes more stable by increasing the radius of the cylinder as the cylinder moves either upward or downward. The effect of the cylinder radius on the stability of the thin film flow becomes less significant as the downward direction velocity of the cylinder increases. Conversely, the radius effect becomes more pronounced as the upward direction velocity of the cylinder increases. (3)Rupture analysis of thin liquid film on cylinder: The occurrence of film rupture is delayed as the value of the micropolar parameter, , is increased. Furthermore, the rupture time of the film flow decreases as the van der Waals potential effect increases. Conversely, increasing the surface tension or the cylinder radius delays the onset of the rupture process.
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Cheng, Po-Jen, and 鄭博仁. "Nonlinear Hydrodynamic Stability Analysis of Gravity-Driven Non-Newtonian Liquid Film Flows." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/21488992840751674269.
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博士國立成功大學
機械工程學系
89
The paper investigates the stability of thin non-Newtonian liquid film flowing down on a vertical wall or cylinder using a long-wave perturbation method to solve for generalized nonlinear kinematic equations with free film interface. To begin with a normal mode approach is employed to obtain the linear stability solution for the film flow. The threshold conditions, the linear growth rate of the amplitudes and the linear wave speeds are obtained subsequently as the by-products of linear solutions. To further investigate practical flow stability conditions, the weak nonlinear dynamics of a film flow is presented by using the method of multiple scales. It is shown that the necessary condition for the existence of such a solution is governed by the Ginzburg-Landau equation. The subcritical stability, subcritical instability, supercritical stability and supercritical explosive state will be obtained from the nonlinear film flow system. Some practical examples will be shown in the present thesis in order to illustrate the effectiveness on stability of the viscoelastic coefficient, the flow index of pseudoplastic liquid, the yield stress of Bingham liquid, the micropolar parameter and the cylinder size on the conclusive results. (1)Stability analysis of a thin viscoelastic film flow When a viscoelastic liquid film flow is modeled as a non-Newtonian flow, it possesses the characteristics of the so-called cross-viscosity and elastic properties. As the gravity-driven fluid is in motion, the flow energy is partially consumed by internal viscous forces and dissipated as heat to the environment, and partially stored as strain energy and the elastic stresses cannot be relaxed at a certain frequency. The degree of stability of the viscoelastic film flow decreases as the value of k increases. (2)Stability analysis of a thin pseudoplastic film flow When a pseudoplastic liquid film flow is modeled as a non-Newtonian flow, it possesses the characteristic of shear thinning effect. Physically, the gravity-driven pseudoplastic fluid of thin film flow will decrease the effective viscosity, it can, therefore, increase the convective motion of flow. The decreasing flow index indeed plays a significant role in destabilizing the flow and is thus of great practical importance. (3)Stability analysis of a thin Bingham plastic film flow For the film flow in stable states, the larger yield stress of the Bingham fluid decreases the convective motion of flow and tends to stabilize the flow. However, the yield stress of the Bingham fluid increases the disturbance energy in unstable states. Therefore, the flow will become relatively unstable as the value of yield stress is increased. (4)Stability analysis of a thin micropolar film flow The effect of the microrotation and couple stress will be taken into account in the Non-Newtonian fluid with the suspension micro-particle. Because the vortex viscosity parameter of the microstructure in micropolar fluid will increase the effective viscosity, it can, therefore, reduce the convective motion of flow. The flow field becomes relatively stable for a larger . (5) Stability analysis of a thin film flowing down on a vertical cylinder When the film flows down the outer surface has a destabilizing effect as the cylinder with a smaller radius . This destabilizing effect occurs because the surface tension will produce large capillary pressure at a smaller radius of curvature. This will induce the capillary pressure and force the fluid trough to move upward to the crest. Thus, the amplitude of the wave is increased.
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Wu, Yi-chin, and 吳宜親. "Three-dimensional analysis on the nonlinear hydrodynamic forces for the trimaran ship advancing in waves." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/81226365217728721353.
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碩士國立成功大學
系統及船舶機電工程學系碩博士班
95
In the paper the three-dimensional source distribution method is applied to solve the nonlinear hydrodynamic forces on the trimaran ship advancing in waves. The nonlinear forces can be divided into two components, i.e. added resistance and lateral drifting force, which are caused by ship motions, radiation force, diffraction force and Froude-krylov force. The fluid considered here are assumed to be irrotational, incompressible and non-viscous and the solutions of the nonlinear hydrodynamic forces are treated in frequency domain. Using the panel method and source distribution method, the related hydrodynamic coefficients can be calculated by the boundary conditions and the ship motions can be solved. Based on the Salvesen’s method, the added resistance and lateral drifting force will be obtained from the ship motions and corresponding potentials. In the paper, the steady flow is also included to check the effect on the nonlinear forces with the different wave headings and different side-hull arrangements. From the comparisons of the theory and experiment, we find that the present technique can well predict the added resistance and lateral drifting force for the trimaran ship advancing in waves.
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Meng, Fantai. "A study on a single-tether spherical point absorber with an asymmetric mass distribution." Thesis, 2020. http://hdl.handle.net/2440/123685.
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The adoption of renewable energy has long been regarded as an effective solution to fulfil the growing demand for electricity and reduce greenhouse gas emissions. Ocean wave energy is a promising and reliable resource in the renewable energy mix, which exhibits higher power density and continuity than solar and wind energy. Furthermore, the overall potential of ocean wave energy is estimated as being much as 3.7 terawatts, which is double the current global demand for electricity. Although the first wave energy converter (WEC) design appeared as early as 1790, the technology of wave energy conversion is still at an early stage of commercialisation. Compared with solar and wind energy plants, the existing WEC systems have relatively small power generation capacity and exhibit greater costs associated with investment, infrastructure and maintenance. Consequently, wave energy conversion is currently at an economic disadvantage in the renewable energy mix. This thesis studies the efficiency improvement of a single-tether submerged spherical point absorbing wave energy converter by utilising an asymmetric mass distributed buoy. The spherical point absorber with asymmetric mass distribution is referred to as SPAMD in the thesis. The main contribution lies in frequency-domain modal analysis, parametric optimisation and high-fidelity modelling of the system. This Ph.D. research answers three questions: (i) What effect does mass distribution have on the dynamics of a submerged spherical buoy; (ii) how does the mass distribution of the buoy affect the power output of the SPAMD in irregular waves; and (iii) do the nonlinear hydrodynamic effects compromise the performance of the SPAMD? To understand the working principle and evaluate the efficiency improvement of the SPAMD, a frequency-domain modal analysis is conducted over typical wave frequencies. The influence of a power take-off device on the performance of the SPAMD is discussed on the basis of a modal analysis. The efficiency improvement over a generic point absorber for regular waves is assessed over different frequency regimes. Recommendations pertaining to the application of an asymmetric mass distributed buoy in wave energy harvesting are provided. The design considerations of the mass distribution of the buoy are also investigated under irregular waves characterised by the Pierson-Moskowitz spectrum. A spectral-domain model, including viscous drag effects, is developed to evaluate the performance of the SPAMD efficiently. Attention is given to the power absorption bandwidth, the mean power output and the dynamic mooring loading caused by the configuration of mass distribution. Suggestions regarding the configuration of the mass distribution of the buoy are provided according to the facility cost and the system performance. The final part of this thesis explores the trajectory and power analysis of the SPAMD in a high-fidelity simulation. A numerical wave tank has been developed from the Navier-Stokes equations, to simulate the fluid-structure interface during the operation of the SPAMD. It was found that the nonlinear hydrodynamics significantly modify the trajectory of the device as the wave height grows. The large change in the motion trajectory of the buoy decreases the efficiency of the converter in terms of wave energy harvesting. The efficiency improvement of the SPAMD in comparison with the generic point absorber is demonstrated in the numerical wave tank experiment.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2020
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Nakhata, Tongchate. "Stability analysis of nonlinear coupled barge motions." Thesis, 2002. http://hdl.handle.net/1957/31491.
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The present research investigates nonlinear barge motions through analyses
of coupled multi-degree-of-freedom (MDOF) deterministic and stochastic models.
Roll-Heave-Sway and other lower-ordered models are developed to predict the
nonlinear motions and analyze the stability of a class of ship-to-shore cargo barges.
The governing equations of motion contain coupled rigid body Roll-Heave-Sway
relations, hydrostatic and hydrodynamic terms. The rigid body relationships are a
part of the general six-degree-of-freedom model. Hydrostatic terms include effects of
the barge's sharp edge and of relative Roll-Heave states. Hydrodynamic terms are in
a "Morison" form. The characteristics of the excitation wave field are based on
linear wave theory.
Predictive capabilities of the Roll-Heave-Sway and the Roll-Heave models
are investigated. System parameters are calibrated to match experimental test results
using several regular wave test cases. Potential theory predictions provide initial
estimates of several key system parameters. With the identified system parameters,
numerical predictions obtained from time domain simulations of both models are
compared with experimental test results for a random wave case, and compared to
each other to investigate the coupling effects of sway on roll and heave motions.
Reliability against capsizing of a barge in random seas is investigated using
stochastic analysis techniques. With the Markov process assumption, the barge
response density to random waves is derived as a solution to the corresponding
Fokker-Planck equation. The path integral solution technique is employed to obtain
numerical solutions for the Roll-Heave and the Roll models. A quasi-2DOF model
is introduced to improve the accuracy of the 1DOF Roll model. The reliability of a
barge in a variety of sea conditions is analyzed as a first passage problem using the
quasi-2DOF model. Mean times to reach specified capsizing probabilities for a
barge operating in sea states 1 through 9 are obtained.Graduation date: 2003
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Narayanan, Suchithra. "Experimental analysis of a nonlinear moored structure." Thesis, 1999. http://hdl.handle.net/1957/33527.
Full textBooks on the topic "Nonlinear hydrodynamic analysis"
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Tsamilis, Sotirios E. Nonlinear analysis of coupled roll/sway/yaw stability characteristics of submersible vehicles. Monterey, Calif: Naval Postgraduate School, 1997.
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Walgraef, D. Spatio-temporal pattern formation: With examples from physics, chemistry, and materials science. New York: Springer, 1997.
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Narayanan, Suchithra. Experimental analysis of a nonlinear moored structure. 1999.
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Walgraef, Daniel. Spatio-Temporal Pattern Formation: With Examples from Physics, Chemistry, and Materials Science (Partially Ordered Systems). Springer, 1996.
Find full textBook chapters on the topic "Nonlinear hydrodynamic analysis"
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Fadeyev, Yu A. "Fourier Analysis of the Hydrodynamic Limit-Cycle Models of Pulsating Stars." In Nonlinear Phenomena in Stellar Variability, 261–67. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1062-4_42.
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Sghir, Radhouane, and Mnaouar Chouchane. "Stability Analysis of an Unbalanced Journal Bearing with Nonlinear Hydrodynamic Forces." In Proceedings of the 9th IFToMM International Conference on Rotor Dynamics, 1081–90. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06590-8_88.
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Sghir, Radhouane. "Nonlinear Analysis of the Effect of Hydrodynamic Forces on the Stability of an Unbalanced Rigid Rotor." In Lecture Notes in Mechanical Engineering, 240–48. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-27146-6_26.
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Lu, Yan Jun, Yong Fang Zhang, Ying Wu Fang, and Heng Liu. "A Method to Determine the Periodic Solution Based on Observed State Information and Nonlinear Analysis of Hydrodynamic Bearing-Rotor System." In Key Engineering Materials, 2475–78. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-456-1.2475.
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Zeidler, Eberhard. "Basic Equations of Hydrodynamics." In Nonlinear Functional Analysis and its Applications, 433–47. New York, NY: Springer New York, 1988. http://dx.doi.org/10.1007/978-1-4612-4566-7_14.
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Taylor, R. Eatock. "Analysis of Non-Linear Wave-Body Interactions Using Finite Elements." In Waves and Nonlinear Processes in Hydrodynamics, 51–62. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0253-4_4.
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Tsarev, S. P. "Classical Differential Geometry and Integrability of Systems of Hydrodynamic Type." In Applications of Analytic and Geometric Methods to Nonlinear Differential Equations, 241–49. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-2082-1_23.
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Trifonova, Tatiana, Sergei Arakelian, Dmitri Trifonov, Sergei Abrakhin, Vyacheslav Koneshov, Alexei Nikolaev, and Mileta Arakelian. "Nonlinear Hydrodynamics and Numerical Analysis for a Series of Catastrophic Floods/Debris (2011–2017): The Tectonic Wave Processes Possible Impact on Surface Water and Groundwater Flows." In New Trends in Nonlinear Dynamics, 213–22. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-34724-6_22.
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RIAHI, D. N. "NONLINEAR STABILITY ANALYSIS AND MODELING FOR CONVECTIVE FLOWS." In Mathematical Modeling and Simulation in Hydrodynamic Stability, 117–48. WORLD SCIENTIFIC, 1996. http://dx.doi.org/10.1142/9789812797308_0006.
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Lachowicz, M. "ASYMPTOTIC ANALYSIS OF NONLINEAR KINETIC EQUATIONS: THE HYDRODYNAMIC LIMIT." In Series on Advances in Mathematics for Applied Sciences, 65–148. WORLD SCIENTIFIC, 1995. http://dx.doi.org/10.1142/9789812831170_0002.
Full textConference papers on the topic "Nonlinear hydrodynamic analysis"
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Koo, W. C., S. J. Kim, and M. H. Kim. "Numerical Analysis of Hydrodynamic Performance of Backward Bent Duct Buoy (BBDB)." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83666.
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The hydrodynamic performance of Backward Bent Duct Buoy (BBDB), a floating-type wave energy converter, was evaluated in the time-domain simulation by using a two-dimensional fully-nonlinear numerical wave tank (NWT) technique. The developed NWT was based on potential theory, boundary element method with constant panels, and the mixed Eulerian-Lagrangian (MEL) approach to capture the nonlinear free-surfaces. The viscous damping at the chamber entrance due to oscillating water column and the shape of body causing generation of vortex shedding were modeled and applied to the free surface boundary condition inside the chamber. The calculated surface elevations inside the chamber with open chamber condition were compared with experimental data to select a proper viscous damping coefficient. Then, the surface elevations with a tuned viscous damping coefficient were calculated for various wave conditions. The results of linear and nonlinear time-domain simulation with two different corner-shaped BBDBs were compared to investigate the mean drift force of BBDB. Energy conservation in the computational domain was checked for all cases.
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He, Cong, Hongyu Xu, and Yaoqiang Zhang. "Analysis of the nonlinear dynamic response of gyroscope rotor system considered Elasto-Hydrodynamic Lubrication." In 3rd International Conference on Mechatronics, Robotics and Automation. Paris, France: Atlantis Press, 2015. http://dx.doi.org/10.2991/icmra-15.2015.140.
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Evstigneev, N. M., N. A. Magnitskii, Theodore E. Simos, George Psihoyios, and Ch Tsitouras. "Nonlinear Dynamics of Laminar-Turbulent Transition in Back Facing Step Problem for Bolzmann Equations in Hydrodynamic Limit." In ICNAAM 2010: International Conference of Numerical Analysis and Applied Mathematics 2010. AIP, 2010. http://dx.doi.org/10.1063/1.3498633.
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Ren, Huilong, Jian Zhang, Guoqing Feng, Hui Li, and Chenfeng Li. "Influence of Nonlinear Mooring Stiffness on Hydrodynamic Performance of Floating Bodies." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79697.
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Coupled dynamic analysis between floating marine structures and flexible members such as mooring lines and risers, is a challenging work in the ocean engineering field. Coupled analysis on mooring-buoy interactions has been paid more and more concern for recent years. For floating offshore structures at sea, the motions driven by environmental loads are inevitable. The movement of mooring lines occurs due to the excitation on the top by floating structures. Meanwhile the lines restrict the buoy’s motion by forces acting on the fareleads. Positioning is the main function of mooring system, its orientation effects can’t be ignored for floating structures such as semi-submersible, FPS, and TLP, especially when the buoy’s equilibrium position shifting to another place. Similar as hydrostatic restoring forces, mooring force related with the buoy’s displacement can be transformed into mooring stiffness and can be added in the differential equations of motion, which is calculated at its equilibrium point. For linear hydrodynamic analysis in frequency domain, any physical quantity should be linear or be linearized, however mooring stiffness is nonlinear in essence, so the tangent or differential stiffness is used. Steel chains are widely used in catenary mooring system. An explicit formulation of catenary mooring stiffness is derived in this article, which consists of coupled relations between horizontal and vertical mooring forces. The effects of changing stiffness due to the shift of equilibrium position on the buoy’s hydrodynamic performance are investigated.
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Pham, Duc, Ningsheng Feng, and Eric Hahn. "The Effect of Cavitation on the Vibration Behaviour of Nonlinear Rotor Bearing Systems." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95131.
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Rotor bearing systems frequently utilise hydrodynamic bearings whose dynamic properties are generally influenced by the bearing reaction forces (which determine the bearing stiffness and damping coefficients). These reaction forces are frequently unknown and are generally determined from the solution of the Reynolds equation using rotor motion measurements as input. Of interest is the attainable accuracy of such bearing force determinations, and for experimental evaluation, a test rig was fabricated, the design specification of which required that the rotor system run stably over its operating speed range. This paper describes the commissioning of this rig for stability purposes with the aid of natural frequency analyses, noting the required design modifications to ensure stable operation. Stability was found to be significantly influenced by the extent of the continuous fluid film in the hydrodynamic circumferentially grooved bearings. It was concluded that the assumption of a 180 degree film extent was totally inappropriate even though the bearing ends were open to the atmosphere, whereas the assumption of fluid film break up at the lubricant saturation vapour pressure proved appropriate for stability predictions provided one ensured that the bearings were flooded. Preliminary bearing force evaluations proved inconclusive, primarily because the self aligning bearings nevertheless experienced angular misalignment; and because there was uncertainty as to how much air was entrained in the bearings, in spite of attempts to prevent air ingress.
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Siddiqui, Mohd Atif, Hui-li Xu, Marilena Greco, and Giuseppina Colicchio. "Analysis of Open-Source CFD Tools for Simulating Complex Hydrodynamic Problems." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18030.
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Abstract OpenFOAM (OF) represents an attractive and widely used open-source environment for simulating complex hydrodynamic scenarios with several implemented numerical methods and wide variety of problems it can be applied to. For commercial and open-source solvers, though, expertise and experience are required to get physical and reliable results. Here, without pretending to be exhaustive, we aim to contribute in highlighting advantages and challenges of some key computational fluid dynamics (CFD)-simulation tools, with focus on the OF platform. We examine the effect of grid type, grid size and time-evolution scheme. Dynamic-mesh techniques and their influence on local and global numerical results are discussed, as well as the use of an overset grid versus a deforming mesh. Lastly, possible error sources in CFD simulations are discussed. These numerical studies are performed investigating two complex hydrodynamic problems: 1. a fully-immersed flapping hydrofoil aimed to generate thrust, 2. a damaged and an intact ship section fixed in beam-sea waves, in forced heave and roll motion in calm water. In the first case, vortex-shedding and wake features are crucial; in the second case, free-surface flow effects play the key role while the importance of vortex-shedding and viscous-flow effects depends on the scenario. The first problem is solved with OF and validated with results from benchmark experiments. The second problem is solved using (A) OF, (B) an in-house CFD solver and (C) a fully-nonlinear potential-flow code. A and B assume laminar-flow conditions and use, respectively, a volume-of-fluid and a level-set technique to handle the free-surface evolution. C is considered to examine importance of nonlinear versus viscous effects for the examined problems. The results are compared against in-house experiments.
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Oberleithner, Kilian, and Christian Oliver Paschereit. "Modeling Flame Describing Functions Based on Hydrodynamic Linear Stability Analysis." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57316.
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Combustion instabilities crucially affect the operational range of modern lean premixed gas turbine combustors and must be avoided or kept at low amplitudes. The main uncertainty of current prediction models is the flame describing function (FDF) that characterizes the flame response to high amplitude acoustic forcing. In this work, we present a new FDF model based on linear hydrodynamic stability analysis. This work is in continuation of an earlier study, where the frequency dependence and saturation of the FDF gain of a perfectly premixed flame was linked to the growth rates of the Kelvin–Helmholtz (KH) instability. In this work, we report on FDF measurements in a newly designed swirl-stabilized combustor. We identify two independent mechanisms that determine the flame response. The first stems from swirl-fluctuations that are generated in the swirler and the second stems from the KH instability. The swirl-fluctuations are approximated by a convective time lag model. The KH instability is predicted from linear hydrodynamic stability analysis based on the time-mean flow measured via PIV. A combination of both models leads to a good quantitative agreement with the measured FDF. Besides the practical advantages of predicting the FDF from stationary flow data, the model reveals the mechanisms driving the saturation of the FDF and guides the way out from the black-box treatment of the nonlinear flame response.
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Wahls, Sander, Markus Bruehl, Yang-Ming Fan, and Ching-Jer Huang. "Nonlinear Fourier Analysis of Free-Surface Buoy Data Using the Software Library FNFT." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18676.
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Abstract Nonlinear Fourier Analysis (NFA) is a powerful tool for the analysis of hydrodynamic processes. The unique capabilities of NFA include, but are not limited to, the detection of hidden solitons and the detection of modulation instability, which are essential for the understanding of nonlinear phenomena such as rogue waves. However, even though NFA has been applied to many interesting problems, it remains a non-standard tool. Recently, an open source software library called FNFT has been released to the public. (FNFT is short for “Fast Nonlinear Fourier Transforms”.) The library in particular contains code for the efficient numerical NFA of hydrodynamic processes that are approximately governed by the nonlinear Schroedinger equation with periodic boundary conditions. Waves in deep water are a prime example for such a process. In this paper, we use FNFT to perform an exemplary NFA of typhoon data collected by wave buoys at the coast of Taiwan. Our goals are a) to demonstrate the application of FNFT in a practical scenario, and b) to compare the results of a NFA to an analysis based on the conventional linear Fourier transform. The exposition is deliberately educational, hopefully enabling others to use FNFT for similar analyses of their own data.
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Chen, Ming, Solomon C. Yim, Daniel Cox, Zhaoqing Yang, and Thomas Mumford. "Hydrodynamic Analysis of Macroalgae Local Model Using Computational Fluid Dynamics." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-19279.
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Abstract In this article, a local scale, fully nonlinear coupled fluid-structural interaction (FSI) sugar kelp model has been developed using a computational fluid dynamics (CFD) method. In this model, to be consistent with available experimental data, the sugar kelp is approximated as elongated rectangles with smoothed isosceles triangles at the ends and a single kelp model with one end fixed in a channel with constant current model is developed. Several different current speeds are simulated, and the resulting drag forces and calculated drag coefficients are validated by comparison with experimental data from the literature. In a previous study, a global scale model was developed using a computational structural dynamics (CSD) method to simulate macroalgae farming system and guide the system configuration design. In the global scale model, the hydrodynamic forces are calculated using Morison’s equation and the kinematics and dynamics of the sugar kelp are simplified and the group of kelps attached to the long line is modeled as a slender structure with the same length and an effective diameter such that the volumes are consistent with the real physical system. This simplified model matches the weight and buoyancy but adjusting the hydrodynamic properties when the general hydrodynamic coefficients are employed. Therefore, optimal hydrodynamic coefficients used in global scale model were determined to obtain the hydrodynamic force more accurately. The validated local scale model is then be applied to determine the hydrodynamic coefficients of the simplified sugar kelp model for global dynamic analysis.
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Kakoty, S. K., S. K. Laha, and P. Mallik. "Stability Analysis of Two-Layered Finite Hydrodynamic Porous Journal Bearing Using Linear and Nonlinear Transient Method." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34416.
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A theoretical analysis has been carried out to determine the stability of rigid rotor supported on two symmetrical finite two-layered porous oil journal bearings. The stability curves have been drawn for different eccentricity ratios and Sommerfeld numbers. The effect of bearing feeding parameter, L/D ratio on the stability is also investigated. This paper also deals with a theoretical investigation of stability using a non-linear transient method. This analysis gives the journal centre locus and from this the system stability can be determined. With the help of graphics, several trajectories of the journal centre have been obtained for different operating conditions. Finally a comparison between single-layered porous bearing and the two-layered porous bearing is presented here.