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E Longatte - One of the best experts on this subject based on the ideXlab platform.
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Parametric study of flow-induced vibrations in cylinder arrays under single-phase Fluid Cross flows using POD-ROM
Journal of Fluids and Structures, 2018Co-Authors: E Longatte, Jean François Sigrist, Erwan Liberge, Marie Pomarede, Aziz HamdouniAbstract:Abstract Modeling numerically Flow-Induced Vibrations in heat exchangers at a microscopic scale requires high computational resources and time which are still unreachable. Therefore model reduction is investigated in the present work in order to address the issue of simulation computational time reduction. In the framework of POD-Galerkin projection methods, the purpose is to propose optimal a posteriori reduction strategies enabling error control on approximation as well as Reduced-Order Model (ROM) interpolation to deal with sensitivity analysis of solutions to parameter perturbations. A multi-phase Fluid–solid POD-Galerkin-based method is proposed for modeling flows and vibrations in cylinder arrangements under single-phase Fluid Cross-flows. Moreover a single-POD basis method is evaluated in the context of ROM interpolation. This work is a first step in the development of robust ROM describing Fluid and solid dynamics in the presence of turbulence, heat transfer effects and large magnitude structure displacements and deformations.
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An algebraic expansion of the potential theory for predicting dynamic stability limit of in-line cylinder arrangement under single-phase Fluid Cross-flow
Journal of Fluids and Structures, 2017Co-Authors: Mustapha Benaouicha, Franck Baj, E LongatteAbstract:Abstract Flow-induced vibration in square cylinder arrangement under viscous Fluid incompressible Cross-flow is investigated in the present work. The purpose is to contribute to better modeling and understanding external Fluid loads exerted on long thin cylinders inducing flow perturbations. Due to high flow confinement, thin cylinders may be subjected to strong vibrations, which may lead to dynamic instability development. A theoretical approach is developed to determine a stability criterion of the dynamical system. The influence of geometric, mechanical and flow parameters such as reduced velocity and pitch ratio is investigated. The proposed model is derived from the potential flow theory and enhanced through an algebraic phase lag model in order to predict the critical limit of the reduced velocity for a square cylinder arrangement submitted to an external in-line Cross flow. A theoretical formulation of the total damping, including added damping in still Fluid, the damping due to Fluid flow and the damping derived from the phase shift between the Fluid load and the tube displacement, is expressed. A function depending on Fluid and structure parameters, such as reduced velocity, pitch ratio and Scruton number is thus obtained. It is shown that this function provides a prediction of the dynamic stability limit of the system for several ranges of the major parameters to be considered. The results are compared to experimental reference solutions and to those provided by other theoretical models. This work proposes a consistent original model based on a potential flow theory enriched by using an algebraic formulation based on standard physical assumptions from literature. The major advantage of this model is due to the fact that it is in the same time robust and very user-friendly from a computational point of view thanks to the potential framework. In order to describe Fluid and solid dynamics in the domain, terms coming from the potential flow theory are estimated by using a finite element method and complementary terms acting on damping are obtained through an algebraic formulation. Therefore this is a convenient way to propose a hybrid numerical / algebraic model for predicting dynamic instability limit in cylinder arrangements.
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large eddy simulation of Fluid elastic instability in square normal cylinder array
Volume 5: High-Pressure Technology; Rudy Scavuzzo Student Paper Competition and 23rd Annual Student Paper Competition; ASME NDE Division, 2015Co-Authors: Vilas Shinde, E Longatte, Franck BajAbstract:Large Eddy Simulations (LES) are performed at low Reynolds number (2000 upto 6000) to investigate the dynamic Fluid-elastic instability in square normal cylinder array for a single-phase Fluid Cross flow. The Fluid-elastic instability is dominant in flow normal direction, at least for all water-flow experiments (Price et al. [18]). The instability appears even in the case of single moving cylinder in an otherwise fixed-cylinder arrangement resulting in the same critical velocity (Khalifa et al. [1]). Therefore, in the present work only a central cylinder out of 20 cylinders is allowed to vibrate in flow normal direction. The square normal (90°) array has 5 rows and 3 columns of cylinders with 2 additional side columns of half wall-mounted cylinders. The numerical configuration is a replica of the experimental setup except for the length of cylinders, which is 4 diameters (4D) in numerical setup against about 8D in the experiment facility. The single-phase Fluid is water. The standard Smagorinsky turbulence model is used for the sub-grid scale eddy viscosity modeling. The numerical results are analysed and compared with the experimental results, for a range of flow velocities in the vicinity of the instability. Moreover, instantaneous pressure and Fluid-force profiles on the cylinder surface are extracted from the LES calculations in order to better understand the dynamic Fluid-elastic instability.Copyright © 2015 by ASME
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Numerical simulation of an elementary Vortex-Induced-Vibration problem by using fully-coupled Fluid solid system computation
International Journal of Multiphysics, 2010Co-Authors: M. Pomarède, E Longatte, Jean François SigristAbstract:Numerical simulation of Vortex-Induced-Vibrations (VIV) of a rigid circular elastically-mounted cylinder submitted to a Fluid Cross-flow has been extensively studied over the past decades, both experimentally and numerically, because of its theoretical and practical interest for understanding Flow-Induced-Vibrations (FIV) problems. In this context, the present article aims to expose a numerical study based on fully-coupled Fluid-solid computations compared to previously published work [34], [36]. The computational procedure relies on a partitioned method ensuring the coupling between Fluid and structure solvers. The Fluid solver involves a moving mesh formulation for simulation of the Fluid structure interface motion. Energy exchanges between Fluid and solid models are ensured through convenient numerical schemes. The present study is devoted to a low Reynolds number configuration. Cylinder motion magnitude, hydrodynamic forces, oscillation frequency and Fluid vortex shedding modes are investigated and the "lock-in" phenomenon is reproduced numerically. These numerical results are proposed for code validation purposes before investigating larger industrial applications such as configurations involving tube arrays under Cross-flows [4].
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Benchmark of Numerical Codes for Coupled CSD/CFD Computations on an Elementary Vortex Induced Vibration Problem
Volume 4: Fluid-Structure Interaction, 2009Co-Authors: Marie Pomarede, E Longatte, Jean-franc¸ois SigristAbstract:Numerical simulation of vortex-induced-vibrations (VIV) of an elastically supported rigid circular cylinder in a Fluid Cross-flow has been thoroughly studied over the past years, both from the experimental and numerical points of view, because of its theoretical and practical interest in the understanding of flow-induced vibrations problems. In this context, the present paper aims at exposing a numerical study based on a coupled Fluid-structure simulation, compared with previously published studies [34], [36]. The computational procedure relies on a partitioned method ensuring the coupling between Fluid and structure solvers. The Fluid solver involves a moving mesh formulation for simulation of the interface motion. Energy exchanges between both systems are ensured through convenient coupling schemes. The present study is devoted to a low Reynolds number configuration ( Re = 100). Cylinder motion magnitude, hydrodynamic forces, oscillation frequency and Fluid vortex shedding modes are investigated with the intention to observe the “lock-in” phenomenon. These numerical simulations are proposed for code validation purposes prior to industrial applications to tube bundle configurations [4].Copyright © 2009 by ASME
E.j. Chapyak - One of the best experts on this subject based on the ideXlab platform.
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Apparent target strength in long-rod penetration
International Journal of Impact Engineering, 1998Co-Authors: R.p. Godwin, E.j. ChapyakAbstract:We investigate the apparent enhancement of target strength in the steady-state Tate model of long-rod penetration. Computing the effective area over which the target behaves as a Fluid provides a satisfactory explanation of the measured effective one-dimensional target strength. Expressing the effective target strength as Rt = aYt, we postulate that a = AeAp, where Yt is the nominal strength; Ae is the effective target Fluid Cross-sectional area and Ap the true projectile Cross-sectional area. For the case of a rod and projectile of the same material, we use the Tate model together with the Birkhoff jet model to show a ≈ 4 is likely. Simultaneously satisfying Newton's Second Law and the Tate model yields a = 4 for purely Fluid behavior, i.e. at high penetrator velocities. By explicitly including strength terms in both Bernoulli's Law and Newton's Second Law, we derive a more general strength multiplier. This multiplier is a function of the penetrator velocity as well as the density and strength of both the penetrator and target. At the velocity threshold for steady-state eroding-rod penetration, a = 2 + 2 √1−YpYt, where Yp is the projectile strength.
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Apparent target strength in long-rod penetration
1996Co-Authors: R.p. Godwin, E.j. ChapyakAbstract:The authors investigate the apparent enhancement of target strength in the steady-state Tate model of long-rod penetration. They show that computing the effective area over which the target behaves as a Fluid provides an explanation of the effective 1-D target strength measured empirically. Expressing the effective target strength as R{sub t} = a {times} Y{sub t}, they postulate that a = A{sub e}/A{sub p}, where Y{sub t} is the nominal strength; A{sub e} is the effective target Fluid Cross-sectional area and A{sub p} the projectile Cross-sectional area. For the case of a rod and projectile of the same material, they use the Tate model together with the jet model of Birkhoff et al. to show a {approx} 4 is likely. Simultaneously satisfying Newton`s Second Law and the Tate model yields a very general derivation of a = 4. By explicitly including strength terms in both the Tate equation and Newton`s Second Law, an even more general a = f(v,{rho}{sub p},{rho}{sub t},Y{sub p},Y{sub t}) can be derived.
Aziz Hamdouni - One of the best experts on this subject based on the ideXlab platform.
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Parametric study of flow-induced vibrations in cylinder arrays under single-phase Fluid Cross flows using POD-ROM
Journal of Fluids and Structures, 2018Co-Authors: E Longatte, Jean François Sigrist, Erwan Liberge, Marie Pomarede, Aziz HamdouniAbstract:Abstract Modeling numerically Flow-Induced Vibrations in heat exchangers at a microscopic scale requires high computational resources and time which are still unreachable. Therefore model reduction is investigated in the present work in order to address the issue of simulation computational time reduction. In the framework of POD-Galerkin projection methods, the purpose is to propose optimal a posteriori reduction strategies enabling error control on approximation as well as Reduced-Order Model (ROM) interpolation to deal with sensitivity analysis of solutions to parameter perturbations. A multi-phase Fluid–solid POD-Galerkin-based method is proposed for modeling flows and vibrations in cylinder arrangements under single-phase Fluid Cross-flows. Moreover a single-POD basis method is evaluated in the context of ROM interpolation. This work is a first step in the development of robust ROM describing Fluid and solid dynamics in the presence of turbulence, heat transfer effects and large magnitude structure displacements and deformations.
R.p. Godwin - One of the best experts on this subject based on the ideXlab platform.
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Apparent target strength in long-rod penetration
International Journal of Impact Engineering, 1998Co-Authors: R.p. Godwin, E.j. ChapyakAbstract:We investigate the apparent enhancement of target strength in the steady-state Tate model of long-rod penetration. Computing the effective area over which the target behaves as a Fluid provides a satisfactory explanation of the measured effective one-dimensional target strength. Expressing the effective target strength as Rt = aYt, we postulate that a = AeAp, where Yt is the nominal strength; Ae is the effective target Fluid Cross-sectional area and Ap the true projectile Cross-sectional area. For the case of a rod and projectile of the same material, we use the Tate model together with the Birkhoff jet model to show a ≈ 4 is likely. Simultaneously satisfying Newton's Second Law and the Tate model yields a = 4 for purely Fluid behavior, i.e. at high penetrator velocities. By explicitly including strength terms in both Bernoulli's Law and Newton's Second Law, we derive a more general strength multiplier. This multiplier is a function of the penetrator velocity as well as the density and strength of both the penetrator and target. At the velocity threshold for steady-state eroding-rod penetration, a = 2 + 2 √1−YpYt, where Yp is the projectile strength.
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Apparent target strength in long-rod penetration
1996Co-Authors: R.p. Godwin, E.j. ChapyakAbstract:The authors investigate the apparent enhancement of target strength in the steady-state Tate model of long-rod penetration. They show that computing the effective area over which the target behaves as a Fluid provides an explanation of the effective 1-D target strength measured empirically. Expressing the effective target strength as R{sub t} = a {times} Y{sub t}, they postulate that a = A{sub e}/A{sub p}, where Y{sub t} is the nominal strength; A{sub e} is the effective target Fluid Cross-sectional area and A{sub p} the projectile Cross-sectional area. For the case of a rod and projectile of the same material, they use the Tate model together with the jet model of Birkhoff et al. to show a {approx} 4 is likely. Simultaneously satisfying Newton`s Second Law and the Tate model yields a very general derivation of a = 4. By explicitly including strength terms in both the Tate equation and Newton`s Second Law, an even more general a = f(v,{rho}{sub p},{rho}{sub t},Y{sub p},Y{sub t}) can be derived.
Jean François Sigrist - One of the best experts on this subject based on the ideXlab platform.
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Parametric study of flow-induced vibrations in cylinder arrays under single-phase Fluid Cross flows using POD-ROM
Journal of Fluids and Structures, 2018Co-Authors: E Longatte, Jean François Sigrist, Erwan Liberge, Marie Pomarede, Aziz HamdouniAbstract:Abstract Modeling numerically Flow-Induced Vibrations in heat exchangers at a microscopic scale requires high computational resources and time which are still unreachable. Therefore model reduction is investigated in the present work in order to address the issue of simulation computational time reduction. In the framework of POD-Galerkin projection methods, the purpose is to propose optimal a posteriori reduction strategies enabling error control on approximation as well as Reduced-Order Model (ROM) interpolation to deal with sensitivity analysis of solutions to parameter perturbations. A multi-phase Fluid–solid POD-Galerkin-based method is proposed for modeling flows and vibrations in cylinder arrangements under single-phase Fluid Cross-flows. Moreover a single-POD basis method is evaluated in the context of ROM interpolation. This work is a first step in the development of robust ROM describing Fluid and solid dynamics in the presence of turbulence, heat transfer effects and large magnitude structure displacements and deformations.
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Numerical simulation of an elementary Vortex-Induced-Vibration problem by using fully-coupled Fluid solid system computation
International Journal of Multiphysics, 2010Co-Authors: M. Pomarède, E Longatte, Jean François SigristAbstract:Numerical simulation of Vortex-Induced-Vibrations (VIV) of a rigid circular elastically-mounted cylinder submitted to a Fluid Cross-flow has been extensively studied over the past decades, both experimentally and numerically, because of its theoretical and practical interest for understanding Flow-Induced-Vibrations (FIV) problems. In this context, the present article aims to expose a numerical study based on fully-coupled Fluid-solid computations compared to previously published work [34], [36]. The computational procedure relies on a partitioned method ensuring the coupling between Fluid and structure solvers. The Fluid solver involves a moving mesh formulation for simulation of the Fluid structure interface motion. Energy exchanges between Fluid and solid models are ensured through convenient numerical schemes. The present study is devoted to a low Reynolds number configuration. Cylinder motion magnitude, hydrodynamic forces, oscillation frequency and Fluid vortex shedding modes are investigated and the "lock-in" phenomenon is reproduced numerically. These numerical results are proposed for code validation purposes before investigating larger industrial applications such as configurations involving tube arrays under Cross-flows [4].