COMPARISON OF NOISE SPECTRA OF THE FLOW PAST A CYLINDER COMPUTED BY DIFFERENT TURBULENCE MODELS

Aero-acoustic features are a contemporary and important topic for many mechanical systems, and include various flow phenomena, such as “singing” of wires, cables, metal rods, antennas, etc. as well as wake shedding from different kinds of blades. The aim of the current computational study is to compare and estimate the reliability of available turbulence and acoustic models in ANSYS FLUENT. A spatial, incompressible, transient flow around a cylinder at relatively low Reynolds number Re = 90000 and Mach number M = 0.2 is used as a benchmark and investigated in detail. Both unsteady Reynolds-averaged Navier-Stokes (URANS) and filtered Navier-Stokes (large eddy simulation, LES) equations are solved and resulting flow fields are compared. In both cases, Ffowcs-Williams and Hawkings (FWH) acoustic model is employed. The presented results include oscillating aerodynamic coefficients, instantaneous and averaged flow field visualizations, noise spectra and overall noise levels. Comparisons between the tested turbulence models confirm that the simpler, computationally less expensive URANS approach captures fewer flow features than LES, as well as the resulting noise frequency components, but is applicable for initial studies. On the other hand, both tested turbulence models underestimate the generated noise by roughly 25%. In can be concluded that the agreement with the corresponding, available experimental data seems acceptable for preliminary analyses. Aerodynamic coefficients can be estimated with more reliability than acoustic quantities.