Simulation of oscillating fluid structure interactions

In this thesis, a numerical investigation of Fluid Structure Interaction (FSI) problems has been carried out. Such Fluid Structure Interactions (FSI) have been the subject of interest in many studies as they are encountered in almost all practical engineering applications. In particular Vortex Induc...

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Main Author: Sarkar, Abhishek.
Other Authors: Jorg Uwe Schluter
Format: Theses and Dissertations
Language:English
Published: 2013
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Online Access:http://hdl.handle.net/10356/51134
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-511342023-03-11T17:34:29Z Simulation of oscillating fluid structure interactions Sarkar, Abhishek. Jorg Uwe Schluter School of Mechanical and Aerospace Engineering DRNTU::Engineering::Mechanical engineering::Fluid mechanics DRNTU::Engineering::Aeronautical engineering::Aerodynamics In this thesis, a numerical investigation of Fluid Structure Interaction (FSI) problems has been carried out. Such Fluid Structure Interactions (FSI) have been the subject of interest in many studies as they are encountered in almost all practical engineering applications. In particular Vortex Induced Vibrations (VIV) are of great interest, as the oscillation of a structure due to the flow can lead to fatigue and even failure. The fluid flow and the motion of the body are strongly coupled because the fluid exerts forces on the body, which in turn affects the flow field. The flow exerts periodic forces on the body due to the vortex shedding and the body tends to oscillate. The wake behind the body changes considerably depending on the lift and drag force coeffcients, amplitude and frequency of oscillation. Thus, understanding the behavior of the turbulent wake behind the body is crucial to the understanding of any VIV problem. In the present study, the methodology for analyzing the turbulent energy budget in the wake of structures immersed in a fluid flow has been developed. The analysis of a periodically excited turbulent mixing layer using Large Eddy Simulations (LES) provides a validation test case to assess the accuracy of this methodology. The determination of large scale quasi-organized coherent structures were done by phase averaging. Then, turbulent energy production and their mutual interactions between the mean flow, the coherent structures, and the random flow is computed using the triple decomposition approach to understand the energy transfer between organized and stochastic turbulent structures. Next, numerical investigations of an elastically mounted circular cylinder undergoing VIV have been carried out. The cylinder motion is restricted to oscillate only in the transverse direction of flow with one degree of freedom. The Immersed Boundary Method (IBM) is used to simulate the moving boundaries, thereby requiring a single cartesian mesh for all time steps. Simulations are carried out at moderate Reynolds number of Re = 8000 with a low mass-damping parameter at different reduced velocities and damping ratios. The response of self-regulating cylinder in cross-flow were compared with the results of another numerical study. The analysis is focused on a cylinder vibrating only in the synchronization region where the frequency of vortex shedding is locked to the frequency of oscillation of the cylinder as this is the most challenging and most hazardous regime. The results give very interesting insight into the wake dynamics of the cylinders undergoing VIV and the flow physics in such Fluid-Structure Interaction problems. The results show that the maximum amplitude of a VIV is limited by the ability of the mean flow to feed energy to the wake vortices. Doctor of Philosophy (MAE) 2013-02-05T04:21:43Z 2013-02-05T04:21:43Z 2012 2012 Thesis http://hdl.handle.net/10356/51134 en 158 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Mechanical engineering::Fluid mechanics
DRNTU::Engineering::Aeronautical engineering::Aerodynamics
spellingShingle DRNTU::Engineering::Mechanical engineering::Fluid mechanics
DRNTU::Engineering::Aeronautical engineering::Aerodynamics
Sarkar, Abhishek.
Simulation of oscillating fluid structure interactions
description In this thesis, a numerical investigation of Fluid Structure Interaction (FSI) problems has been carried out. Such Fluid Structure Interactions (FSI) have been the subject of interest in many studies as they are encountered in almost all practical engineering applications. In particular Vortex Induced Vibrations (VIV) are of great interest, as the oscillation of a structure due to the flow can lead to fatigue and even failure. The fluid flow and the motion of the body are strongly coupled because the fluid exerts forces on the body, which in turn affects the flow field. The flow exerts periodic forces on the body due to the vortex shedding and the body tends to oscillate. The wake behind the body changes considerably depending on the lift and drag force coeffcients, amplitude and frequency of oscillation. Thus, understanding the behavior of the turbulent wake behind the body is crucial to the understanding of any VIV problem. In the present study, the methodology for analyzing the turbulent energy budget in the wake of structures immersed in a fluid flow has been developed. The analysis of a periodically excited turbulent mixing layer using Large Eddy Simulations (LES) provides a validation test case to assess the accuracy of this methodology. The determination of large scale quasi-organized coherent structures were done by phase averaging. Then, turbulent energy production and their mutual interactions between the mean flow, the coherent structures, and the random flow is computed using the triple decomposition approach to understand the energy transfer between organized and stochastic turbulent structures. Next, numerical investigations of an elastically mounted circular cylinder undergoing VIV have been carried out. The cylinder motion is restricted to oscillate only in the transverse direction of flow with one degree of freedom. The Immersed Boundary Method (IBM) is used to simulate the moving boundaries, thereby requiring a single cartesian mesh for all time steps. Simulations are carried out at moderate Reynolds number of Re = 8000 with a low mass-damping parameter at different reduced velocities and damping ratios. The response of self-regulating cylinder in cross-flow were compared with the results of another numerical study. The analysis is focused on a cylinder vibrating only in the synchronization region where the frequency of vortex shedding is locked to the frequency of oscillation of the cylinder as this is the most challenging and most hazardous regime. The results give very interesting insight into the wake dynamics of the cylinders undergoing VIV and the flow physics in such Fluid-Structure Interaction problems. The results show that the maximum amplitude of a VIV is limited by the ability of the mean flow to feed energy to the wake vortices.
author2 Jorg Uwe Schluter
author_facet Jorg Uwe Schluter
Sarkar, Abhishek.
format Theses and Dissertations
author Sarkar, Abhishek.
author_sort Sarkar, Abhishek.
title Simulation of oscillating fluid structure interactions
title_short Simulation of oscillating fluid structure interactions
title_full Simulation of oscillating fluid structure interactions
title_fullStr Simulation of oscillating fluid structure interactions
title_full_unstemmed Simulation of oscillating fluid structure interactions
title_sort simulation of oscillating fluid structure interactions
publishDate 2013
url http://hdl.handle.net/10356/51134
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