Free-stream Turbulence Effects on Vortex Shedding: A CFD Study

Abstract

This study investigates the nuances of the effects of free-stream turbulence (FST) on bluff bodies using a method that blends computational fluid dynamics (CFD) simulations and synthetic turbulence generation techniques. This research focuses on using the divergence-free synthetic eddy method (DFSEM), a synthetic turbulence generator for the inlet condition, for large eddy simulation (LES) using Open-FOAM. This open-source CFD solver leverages the finite volume method (FVM). DFSEM mimics the structural properties of turbulence by carefully injecting randomly generated eddies into the velocity field, resulting in turbulence-like fluctuations. The parameters of the approach, such as mean velocity, integral length scale, and Reynolds stress, are critical in determining turbulent flow properties. The flow is treated as homogeneous isotropic turbulence (HIT), and the turbulence intensity is assumed to be 10%. The simulations in this work are focused on bluff bodies, particularly cylinders and spheres, to evaluate the effect of free-stream turbulence (FST) on their aerodynamic properties. The study investigates how synthetic turbulence affects the vortex-shedding phenomenon around these bluff bodies. The findings emphasize the complex interplay between free-stream turbulence and bluff body aerodynamics, providing essential insights into flow behaviour and shedding light on funda-mental features of turbulent flow dynamics. The study’s significance goes beyond fundamental research, with potential applications ranging from sports aerodynamics, particularly in tennis, where seam structure is critical, to advances in LES techniques. By explaining the complex interaction between free-stream turbulence and bluff body aerodynamics within the LES framework, this study sets the way for future research into turbulence modelling and aerodynamic optimization, providing significant insights into real-world flow phenomena.