Investigation of the influence of Lighthill's source term parts in an automotive turbocharger compressor

Lighthill’s inhomogeneous wave equation in combination with the Finite Element (FE) method is an adequate approach for computing pressure fluctuations inside a turbocharger compressor, giving multiple advantages. Firstly, computing fluctuations using FE are not influenced by numeric dissipation. Furthermore, this methodology allows investigating the influence of the additions connected to the compressor by interpolating Lighthill’s source terms onto different propagation grids. Lighthill’s source term consists of three different main parts (1) the Reynolds stress term, (2) the excess term, and (3) the viscous term. The influence of those three source term parts on propagation simulations in the inlet and outlet region of turbocharger compressors are investigated by comparing them with flow simulation results and measurements of a cold gas test rig. Furthermore, also the Ffowcs Williams-Hawkings approach was used applied for comparing simulation results.