Estimation of the frequency boundaries of the inertial range for wind noise spectra in anechoic wind tunnels

Wind noise generated by the intrinsic turbulence in the flow can affect the outdoor noise measurements. Various attempts have been made to investigate the wind noise generation mechanism. Wind noise spectra in anechoic wind tunnels can be divided into three frequency regions. In the low frequency region known as the energy-containing range, the wind noise spectrum does not change significantly with frequency. In contrast, in the middle frequency region (or inertial range) the decay rate of the wind noise spectrum curve follows the 7/3 power law, but in the high frequency region (or dissipation range) the decay rate of the wind noise spectrum curve is faster than the 7/3 power law. The boundaries of the 7/3 power law frequency range depend on the Reynolds number; however, no exact value is known according to current literature. This paper proposes a method for predicting the boundary values based on the energy cascade theory. Large eddy simulations of free jet were performed to validate the proposed method and the results were found to be in reasonable agreement with existing experiment measurements obtained in an anechoic wind tunnel. Additional simulations were also conducted with different inflow entrance sizes to further verify the predictions from the proposed method.