Shear layer correction methods for open-jet wind tunnel phased array test

To identify the true location of the noise sources, the shear layer effect must be taking into account when conducting the microphone array test in open-jet wind tunnels. An experimental study for the shear layer correction was performed in the 0.55m×0.40m aero-acoustic tunnel of China Aerodynamics Research and Development Center(CARDC). The shear layer velocity profiles, source-receiver delay times and source identification results were obtained. The Gortler's velocity-profile solution was validated and four different shear layer correction methods were compared and analyzed on the basis of the experimental results. The research results show that:the velocity-profile experimental data agrees well with calculations when the self-similar parameters σ=9, ξ₀=0.2 are chosen, and the relationship between the fitted shear layer thickness and the axial distance data can be presented by the equation y=0.15x; Ma ≤ 0.3 and the measurement angle θ_m within 40°~140°, the relative calculation error of the delay time of different shear layer correction methods is smaller than 1%; the accuracy of the other three methods are quite close to the Amiet 2D method. A fast ray tracing method that is 100 times faster than the conventional ray tracing method is proposed, which makes the ray tracing method applicable for on-line microphone array data processing.