Numerical simulation of multistage turbine sound generation and propagation

A numerical method has been developed to calculate the noise within a turbine or a compressor by means of CFD (Time Linearized Euler Code). The noise generation, caused by the interaction of neighbouring cascades, can be calculated as well as the noise propagation within the turbomachine. Numerical results obtained by this method are compared to measurements. The CFD results are qualitatively in good agreement with the measurements. For low azimuthal mode orders at BPF1, the computed modal sound power levels at the turbine exit are about 5 to 10 dB too high compared with measurements further downstream in the exhaust duct. Especially the cut-on, cut-off behaviour of the modes in the duct is simulated successfully.