Sound-Based Calculation of Convective Velocities of Turbulent Vortices in Channel Flows

This study investigates turbulent channel flows and their associated acoustic fields, focusing on the interaction between turbulent structures and their imprints on channel walls. A channel flow at was simulated using Large Eddy Simulation (LES). The total sound was decomposed into compressible and incompressible components, derived respectively from acoustic perturbation wave equations and incompressible flow equations. The analysis revealed that at low Mach numbers, incompressible pressure fluctuations, known as pseudo-sound, dominate the total sound spectrum. These fluctuations arise from the convection of vortices along channel walls and leave measurable imprints. By analyzing wall pressure signals collected via aligned point probes, the convective velocities of flow structures across varying length scales were determined. For large, energy-dominant structures (integral length scales), the convective velocities ranged from ۰.۶U to ۰.۸U, where U is the bulk velocity of the channel. These results, obtained through convective ridge analysis using a ۲D Fast Fourier Transform, provide valuable insights into the interplay between turbulence, wall pressure fluctuations, and flow dynamics.

Keywords:

Channel flow , large eddy simulation , Aeroacoustics , Flow measurement , Convective velocity , Pseudo Sound , Acoustic Pressure