Modeling the Turbulence Spectrum Dissipation Range for Leading-Edge Noise Prediction
Fernanda L. dos Santos, Laura Botero-Bolívar, Cornelis H. Venner, Leandro D. de Santana
Abstract
Noise pollution caused by inflow turbulence is a major problem in many applications, e.g., propellers and fans. The Amiet leading-edge noise prediction model is widely applied in the design of silent propellers and fans, strongly relying on the accuracy of the inflow turbulence spectrum. The von Kármán energy spectrum accurately models the energy-containing range and inertial subrange of the turbulence spectrum. However, this model does not incorporate the dissipation range of the turbulent energy and leads to incorrect far-field noise estimates in the high-frequency range. In this study, empirical formulations are presented for the dissipation frequency and the dissipation range based on experimental data. Two passive grids were used to generate nearly isotropic inflow turbulence, which was characterized by hot-wire anemometry. These results showed that the dissipation frequency depends on the intensity of the velocity fluctuations and on the freestream velocity. The expressions proposed to predict the dissipation frequency and the dissipation range had a fairly good agreement with the measured data in this research and with experimental data from the literature. The predicted leading-edge noise is significantly affected by the dissipation range, causing a decrease in level of up to 17 dB for the highest frequencies.