Aeroacoustics Investigation of an Uncontrolled and a Controlled Backward-Facing Step with Large Eddy Simulation

Abstract

In this study, 3D flow over backward-facing step is solved for low Mach number. Large Eddy Simulation is used to resolve turbulent features into the flow field. Numerical results of turbulent flow field are compared with experimental velocity profiles for different stations and those are validated. Additional to accounting a flow field, sound levels for different located receivers due to backward-facing step flow are determined using Acoustic Analogy (AA) which is firstly proposed by Lighthill. Unsteady flow field variables obtained from computational fluid dynamics commercial code is used as input in Ffowcs Williams-Hawkings (FW-H) Equation, which is an extended version of Lighthill equation. Additionally, some active flow control methodologies are carried out to a flow field to understand better relations between flow controls and acoustic results. These flow control techniques are the suction and blowing with different magnitudes at the bottom of backward-facing step. The controlled cases are also compared with experimental flow field results and validated. Acoustic results are plotted in frequency and time domain. Different active control effects on acoustic results are evaluated and interpreted.