Numerical prediction of noise generated from a box fan

The noise generated from a box fan is numerically predicted with two approaches. The first one is the FW-H method that can simulate flow and acoustic together by the flow solver scFLOW but assumes sound propagation in free-space. The second one is the ring of dipoles method that is a hybrid approach between the flow solver scFLOW and the acoustic solver Actran. These approaches are validated for small box fans of two different blade configurations with experimental data available for comparison. An incompressible unsteady LES solver with WALE model is used with a fine mesh to solve unsteady flow fields. The numerical results show quantitatively agreement of the pressure rise performance with the experimental results and that the ring of dipoles method gave closer result to the experiment than the FW-H method especially on the low frequency range. Also, we show that the flow rate dependence of the radiated sound pressure of the experiment can be qualitatively well captured with the ring of dipoles method. Finally, we discuss the causes of the different sound characteristics with different blade configurations.