The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
K Fujimura - One of the best experts on this subject based on the ideXlab platform.
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nonlinear critical reynolds number of a stratified Plane Poiseuille Flow
Physics of Fluids, 1996Co-Authors: H S Li, K FujimuraAbstract:The minimum Reynolds number, ReNc, below which all the two‐dimensional and monochromatic wave disturbances decay, is studied numerically for a thermally stratified Plane Poiseuille Flow. The ReNc is found to be sensitive to the change of Prandtl number P. Under unstable stratification with Rayleigh number just below critical, ReNc≂1000 is found for P≤10−3.
George Papadakis - One of the best experts on this subject based on the ideXlab platform.
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OPTIMAL CONTROL OF Plane Poiseuille Flow
2020Co-Authors: J. Mckernan, James F. Whidborne, George PapadakisAbstract:This paper describes the design of optimal linear quadratic controllers for 2D Plane Poiseuille Flow, and subsequent verification using a finite-volume full Navier-Stokes solver, at both linear and non-linear levels of initial conditions. For linear magnitude initial conditions, open and closedloop finite-volume solver results agree well with a linear simulation. The controllers stabilize the Flow in both cases.
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minimizing transient energy growth in Plane Poiseuille Flow
Proceedings of the Institution of Mechanical Engineers Part I: Journal of Systems and Control Engineering, 2008Co-Authors: James F. Whidborne, J. Mckernan, George PapadakisAbstract:The feedback control of laminar Plane Poiseuille Flow is considered. In common with many Flows, the dynamics of Plane Poiseuille Flow is very non-normal. Consequently, small perturbations grow rapidly with a large transient that may trigger non-linearities and lead to turbulence, even though such perturbations would, in a linear Flow, eventually decay. This sensitivity can be measured using the maximum transient energy growth. The linearized Flow equations are discretized using spectral methods and then considered at one wave-number pair in order to obtain a model of the Flow dynamics in a form suitable for advanced control design. State feedback controllers that minimize an upper bound on the maximum transient energy growth are obtained by the repeated solution of a set of linear matrix inequalities. The controllers are tested using a full Navier-Stokes solver, and the transient energy response magnitudes are significantly reduced compared with the uncontrolled case.
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linear quadratic control of Plane Poiseuille Flow the transient behaviour
International Journal of Control, 2007Co-Authors: J. Mckernan, James F. Whidborne, George PapadakisAbstract:This paper describes the design of optimal linear quadratic controllers for single wavenumber-pair periodic 2-D disturbances in Plane Poiseuille Flow, and subsequent verification using a finite-volume full Navier–Stokes solver, at both linear and non-linear levels of initial conditions selected to produce the largest linear transient energy growth. For linear magnitude initial conditions, open and closed-loop finite-volume solver results agree well with a linear simulation. Transient energy growth is an important performance measure in fluid Flow problems. The controllers reduce the transient energy growth, and the non-linear effects are generally seen to keep energy levels below the scaled linear values, although they do cause instability in one simulation. Comparatively large local quantities of transpiration fluid are required. The modes responsible for the transient energy growth are identified. Modes are shown not to become significantly more orthogonal by the application of control. The synthesis of...
F. Pontiga - One of the best experts on this subject based on the ideXlab platform.
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destabilization of Plane Poiseuille Flow of insulating liquids by unipolar charge injection
Physics of Fluids, 1997Co-Authors: J.l. Lara, A. Castellanos, F. PontigaAbstract:The electrohydrodynamic instabilities of Plane Poiseuille Flow when subjected to an orthogonal arbitrary unipolar injection of charge has been studied. Appropriate boundary conditions for the perturbed charge density in the space charge limited current regime in the presence of forced Flows has been derived. The effect of the injection level on the stability of the Flow is analyzed, as well as the role played by the ratio of the hydrodynamic to the true ionic mobility. It is shown that in the low Reynolds number region traverse rolls are destabilized more strongly as the ratio of mobilities decreases.
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Influence of unipolar charge injection on the stability of Plane Poiseuille Flow
ICDL'96. 12th International Conference on Conduction and Breakdown in Dielectric Liquids, 1996Co-Authors: J.l. Lara, A. Castellanos, F. PontigaAbstract:The electrohydrodynamic instabilities of Plane Poiseuille Flow when subjected to an arbitrary unipolar injection of charge has been studied. The electric field is applied orthogonal to the direction of the forced Flow. Particular attention has been given to the role of the injection level and the ratio of the hydrodynamic to the ionic mobility.
Herbert Werner - One of the best experts on this subject based on the ideXlab platform.
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ECC - An LPV gain scheduling approach to transition control in Plane Poiseuille Flow
2009 European Control Conference (ECC), 2009Co-Authors: Saulat S. Chughtai, Herbert WernerAbstract:This paper presents the synthesis of a gain scheduled controller - parameterized by the Reynolds number - for transition control in Plane Poiseuille Flow. In a real system, the Reynolds number is time-varying - it changes with the speed of Flow. The problem considered here is to prevent the transition from laminar to turbulent Flow at the very onset of turbulence, when the velocity of Flow is changing with time. For this problem a gain scheduled controller, parameterized by the Reynolds number, is proposed. A linear parameter-varying (LPV) model of Plane Poiseuille Flow parameterized by the time-varying Reynolds number is first obtained, which is used to synthesize a gain scheduled control law. Simulation results show that this control scheme can to a significant degree reject disturbances with time-varying Reynolds number.
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An LPV gain scheduling approach to transition control in Plane Poiseuille Flow
2009 European Control Conference (ECC), 2009Co-Authors: Saulat S. Chughtai, Herbert WernerAbstract:This paper presents the synthesis of a gain scheduled controller - parameterized by the Reynolds number - for transition control in Plane Poiseuille Flow. In a real system, the Reynolds number is time-varying - it changes with the speed of Flow. The problem considered here is to prevent the transition from laminar to turbulent Flow at the very onset of turbulence, when the velocity of Flow is changing with time. For this problem a gain scheduled controller, parameterized by the Reynolds number, is proposed. A linear parameter-varying (LPV) model of Plane Poiseuille Flow parameterized by the time-varying Reynolds number is first obtained, which is used to synthesize a gain scheduled control law. Simulation results show that this control scheme can to a significant degree reject disturbances with time-varying Reynolds number.
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Transition control of Plane Poiseuille Flow - a spatially interconnected model
2008 47th IEEE Conference on Decision and Control, 2008Co-Authors: Saulat S. Chughtai, Herbert WernerAbstract:This paper proposes a new mathematical model for the transition control problem in Plane Poiseuille Flow. Most of the previously proposed models are based on pseudospectral approaches and are valid only for a single spatial wave number. In this work we propose a new model which is based on a finite difference approach in streamwise direction and a spectral approach in wall normal direction. The model obtained is valid for all spatial frequencies and can be used for the synthesis of controllers for Flow control problems, using some recently developed ideas for spatially interconnected systems. Since these controllers are designed in physical domain they are simple to implement using MEMS arrays. The model is compared with results obtained with previously proposed models and is found to be in good agreement with them. To illustrate its usefulness, a stabilizing dynamic output feedback controller is designed for a Reynolds number of 6000.
Dan S Henningson - One of the best experts on this subject based on the ideXlab platform.
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Spatial Evolution of Disturbances in Plane Poiseuille Flow
Transition Turbulence and Combustion, 1994Co-Authors: Peter J. Schmid, Anders Lundbladh, Dan S HenningsonAbstract:The spatial evolution of disturbances in Plane Poiseuille Flow is considered. For disturbances governed by the linearized equations potential for significant transient growth of the amplitude has been found. The maximum amplification occurs for disturbances with zero or low frequencies. Spatial numerical simulations of the complete transition scenario involving a pair of oblique waves have also been conducted. A modal decomposition indicates that non-linear excitation of the transient growth is responsible for the rapid emergence of low-frequency structures. Physically, this results in streaky Flow structures, as seen from the results of a numerical amplitude expansion. Thus, this spatial transition scenario has been found to be similar to the corresponding temporal one (Schmid & Henningson, 1992).
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Turbulence characteristics inside a turbulent spot in Plane Poiseuille Flow
Turbulent Shear Flows 7, 1991Co-Authors: Dan S HenningsonAbstract:Turbulence characteristics inside a turbulent spot in Plane Poiseuille Flow are investigated by analyzing a database obtained from a direct simulation. The spot area is divided into two distinct regions—a turbulent area and a wave area. It is found that the Flow structures inside the turbulent area have strong resemblance to those found in fully-developed turbulent channel Flow. A suitably defined mean and r.m.s. fluctuations as well as the internal shear-layer structures are found to be similar to the turbulent counterpart. The r.m.s. fluctuations and Reynolds stress are found to be higher in the wave area, and the shear-layer structures are similar to those observed in the secondary instability of two-dimensional Tollmien-Schlichting waves.
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on turbulent spots in Plane Poiseuille Flow
Journal of Fluid Mechanics, 1991Co-Authors: Dan S HenningsonAbstract:Turbulence characteristics inside a turbulent spot in Plane Poiseuille Flow are investigated by analysing a database obtained from a direct numerical simulation. The spot is found to consist of two distinct regions ― a turbulent area and a wave area. The Flow inside the turbulent area has a strong resemblance to that found in the fully developed turbulent channel
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on turbulent spots in Plane Poiseuille Flow
STIN, 1991Co-Authors: Dan S HenningsonAbstract:Turbulence characteristics inside a turbulent spot in Plane Poiseuille Flow are investigated by analyzing a database obtained from a direct numerical simulation. The spot is found to consist of two distinct regions - a turbulent area and a wave area. The Flow inside the turbulent area has a strong resemblance to that found in the fully developed turbulent channel. Suitably defined mean and r.m.s. fluctuations as well as the internal shear-layer structures are found to be similar to the turbulent counterpart. In the wave area the inflexional mean spanwise profiles cause a rapid growth of oblique waves, which break down to turbulence. The breakdown process of the oblique waves is reminiscent of the secondary instability observed during transition to turbulence in channel and boundary-layer Flows. Other detailed characteristics associated with the Poiseuille spot are presented and are compared with experimental results.