Numerical Investigation of Aerodynamic Noise and Wake Flow Produced by Porous-Coated Square Cylinders

Kurzfassung

Three-dimensional large-eddy simulation (LES) of incompressible turbulent flow over a porous-coated square cylinder is performed at Re = 2.2 x 10^4. The porous medium is modelled via a Darcy-Forchheimer volume-averaged momentum sink, parameterised by the static airflow resistivity sigma of two polyurethane foam grades, sigma = 700 and 4000 Pa s m^-2. Solid baseline and porous-coated cylinders are compared at incidence angles alpha = 0 degrees and 45 degrees. Far-field noise is predicted via the Ffowcs-Williams-Hawkings (FW-H) analogy.

The porous coating suppresses the tonal vortex-shedding peak by up to 24 dB at 0 degrees and 8 dB at 45 degrees, attenuates peak streamwise turbulence intensity by more than 50 percent, and reduces longitudinal integral length scales in the wake by a factor of ten. Space-time correlations confirm destruction of spatially coherent convecting structures. A Curle-scaling framework accurately predicts the observed tonal attenuation from two LES-derived quantities, providing a mechanistic link between porosity and noise reduction.