Hybrid CFD/FEM calculations for the aero- acoustic noise radiated from a radial fan

In this work, hybrid numerical simulations for the aeroacoustic noise of a radial fan are presented. The geometry of the problem is set up according to an experimental technique: the so-called “InDuct” method described by the industrial norm DIN EN ISO 5136. Three slit-tube microphones inside a circular duct are used to monitor the far-field noise levels. The operating radial fan has a diameter of 200 mm and is of backward-curved type with nine blades. The direct fluid dynamics simulations for the whole system are computationally expensive. Hence, a hybrid approach is employed for the aeroacoustic noise. The near field pressure and velocity values are computed with CFD (using ANSYS software), and the far field acoustic pressure is evaluated performing a coupling of the numerical code with the finite element software COMSOL. In particular, the Stress Blended Eddy Simulation (SBES) is employed in CFD computations. A virtual interface near the beginning section of the duct is used for the data exchange. The acoustic pressure at the locations of probe microphones in the far-field is computed using the FEM. Sound pressure levels inside the duct predicted by these numerical methods are presented and comparison of the numerical results with the experimental values is also shown.