Computation of Aeolian Tone Noise from Twin Cylinders by Using Grid-Optimized Dispersion-Relation-Preserving Schemes with Immersed Surface Dipole Model

Grid-Optimized Dispersion-Relation-Preserving (GODRP) schemes are used for the computation of category 5, problem 1 in 4th CAA Workshop. Tam's DRP scheme is implemented only on a uniform Cartesian grid while practical problems in aeroacoustics are seldom confined to uniform Cartesian geometry, with the associated computational grids usually being non-uniform or curvilinear. The GODRP schemes have been developed with grid optimization algorithm to make finite difference equations possess the same dispersion relations as the corresponding partial differential equations on general geometries. Acoustic/viscous splitting techniques with immersed surface dipole model (ISDM) are utilized to solve the sound generation and propagation in viscous, low-Mach number flows for which direct computation of the aerodynamic noise remains difficult because of the large computing resources, the expensive cost and physical/numerical issues inherent in CAA. The ISDM is recently developed for the efficient computation of aerodynamic noise generation and propagation in low Mach number flows in which dipole source, originating from unsteady pressure fluctuation on a solid surface, is known to be more efficient than quadrupole sources. The multi-scale overset grid technique is also applied to resolve the complex geometries. Through the illustrative application to the benchmark problem, it will be shown that the current methods can broaden the application area of computational aeroacoustic techniques to practical aeroacoustic phenomena, enhancing both the speed and accuracy of the computation.