Direct and integral noise computation of two square cylinders in tandem arrangement

The present paper presents a comparison between two different approaches for calculating far-field noise of two square cylinders in tandem arrangement. Experimental data show that a flow past such an arrangement results in aeolian tones as well as broadband noise. The turbulent flow past the cylinders is computed using a compressible solver for low-Mach number flows. In order to validate the direct computation of acoustic waves, the complete span including endplates is calculated. Wind tunnel measurements show two different but stable flow states past the cylinders: a quiet state, where no vortex shedding is present in the wake of the upstream cylinder, and a loud state, where separated shear layers flow into the gap between the cylinders intermittently. Different initialisations of the velocity field are used in order to capture both flow states. Mean flow quantities as well as surface pressure spectra are compared to wind tunnel measurements. Far-field noise is calculated directly using the compressible solver, as well as indirectly using a hybrid method based on a Ffowcs Williams Hawkings formulation for stationary rigid surfaces. Far-field spectra and directivity patterns are compared to wind tunnel measurements. Results of both methods show good agreement with experimental data.