Three-dimensional Numerical Simulations and Proper Orthogonal Decomposition Analysis of Flow Around a Flexibly Supported Circular Cylinder

Abstract

Numerical simulations of turbulent flow around stationary and vibrating cylinders at Re = 3900 are performed using the Large Eddy Simulation (LES) approach. Detailed convergence and validation studies confirm feasibility of the present model to accurately predict the Vortex-Induced Vibrations (VIV) and turbulent wake characteristics. The thesis is divided into seven chapters. First a brief introduction to the topic is given. Chapter 2 gives a brief review of the theory for flow around circular cylinders. In chapter 3 the theory of Computational Fluid Dynamics (CFD) is given. In chapter 4 a series of simulations for a stationary cylinder configuration with different mesh and time step parameters are performed to find an optimal balance between the computational cost and accuracy. Furthermore, simulation results are compared with an extensive dataset from multiple experimental studies showing a very good agreement of the present simulation results with the experimental data. In chapter 5 simulations of a self-excited cylinder vibrating in the cross-flow direction are performed at three different values of reduced velocity. The flow fields are analyzed and different vortex shedding modes are categorized and then compared with the vortex shedding map derived from forced oscillation tests. Proper Orthogonal Decomposition (POD) is performed on sampled data in the wake of the cylinder to analyze the turbulent flow. The present numerical model is found to give accurate predictions with respect to essential parameters affecting the fluid-structure interaction of circular cylinder in the subcritical regime. In chapter 6 a conclusion of the results is presented and chapter 7 presents recommendation for future work.