A hybrid prediction method for low-subsonic turbulent flow noise

A hybrid method is proposed for prediction of low-subsonic, turbulent flow noise. In this method, the noise sources in the near wall turbulences or in the wake are computed by the incompressible large eddy simulation (LES), while the generation and propagation of the acoustic waves are solved by the linearized perturbed compressible equations (LPCE), with acoustic sources represented by a material derivative of the hydrodynamic pressure, DP/Dt. The accuracy of the present method is critically assessed for two experiments conducted at the Ecole Centrale de Lyon and the University Erlangen, where aeroacoustic measurements were taken for (i) the flat plate self-noise at zero angle of attack (Rec=1.3×105,M=0.06) and (ii) the forward-facing step noise (Reh=8000,M=0.03), respectively. The noise sources are identified and analyzed further to determine their spectral-dependent, spanwise coherence functions, γij of the wall pressure fluctuations, in order to quantify the sizes of the noise sources. The far-field sound pressure level (SPL) spectra predicted by the present method are found in excellent agreement with the experimental measurements.