Simulation of the Flow and Acoustic Field of a Fan

The focus of the present work is the steady and unsteady numerical simulation of flow field and flow-induced acoustic field of a fan using a hybrid approach. The steady simulation of the flow field is carried out with a realizable k-epsilon turbulence model. In a second step the result are used for the evaluation of the acoustic sources, which are used as input data of the Broadband Noise Model. From this computational acoustics (CA) we get a qualitative map of acoustic power level in the entire computational domain. From steady flow fields with different mass flows as inlet boundary condition the characteristic curve of the fan (pressure vs. mass flow) is evaluated.

In the unsteady simulation, the acoustic noise propagation is computed using the Ffowcs Williams and Hawkings (FW-H) analogy. The source term in the acoustic propagation equation is achieved from the CFD result. With this unsteady simulation the transient acoustic power level in every location can be calculated, which enables a FFT-analysis of the acoustic field.