A Parallel CFD-CAA computation of aerodynamic noise for cylinder wake-airfoil interactions

The various comparisons of hydrodynamic and aero acoustic results with the experimental data showing that the computational methodology used in the present study is reasonably consistent and accurate. Some discrepancy observed in the computational results is primarily because of the grid resolutions for both flow and acoustics. Another possibility is that any form of subgrid scale model was not used in the present large eddy simulation (LES). The simulation pointed out that the whole flow field and tonal noise are governed by the vortex shedding of the rod. The generation mechanism of the tonal noise is the swinging of the stagnation point around the leading edge of the airfoil through periodic interactions of the Karman vortex with the airfoil. The broadband noise is generated by several sources: turbulent wakes between the rod and the airfoil (large amount of volume sources), their interaction with the airfoil leading edge, and the trailing-edge scattering of eddies within the boundary layers over the airfoil. The span-wise coherence functions of the wall pressure are rapidly decaying in most frequencies. Thereby, the span-wise coherence lengths are smaller than the rod diameter in most cases. © 2007