An experimental investigation of turbulent flow over two-dimensional obstacles on a flat plate

Aeroacoustic and aerodynamic characteristics of the turbulent boundary layer encountering a large obstacle are experimentally investigated in this work. Obstacles with a uniform square and semicircular cross-section mounted on a flat plate are studied in wind tunnel tests, with particular interests in the shear layer characteristics, wall pressure fluctuations, and far-field noise induced by the obstacles. Synchronized measurements of the far-field noise and the wall pressure fluctuations were conducted. Additionally, the streamwise and wall-normal velocity fluctuations behind the obstacle were measured using an X-wire probe. The measured velocity profiles, spectra and the wall pressure spectra are compared, showing that the square obstacle has a significant impact on both the turbulent flow and far-field noise. The large-scale vortical structures shed from the obstacles can be identified in the wall pressure spectra, the streamwise velocity spectra, and the wall pressure coherence analysis. Within the shear layer, the pairing of spanwise vortices occurs, and the frequency of the broadband peak in the wall pressure coherence decreases as the shear layer grows downstream. The eddy convective velocities of large-scale vortical structures inside the shear layer were analyzed based on the wall pressure fluctuations. © INTER-NOISE 2021 .All right reserved.