A novel trailing edge noise control technique based on upstream manipulation of large coherent turbulent structures using two dimensional surface treatments has been proposed and tested. To demonstrate the capabilities of the proposed trailing edge noise control technique, a long flat-plate model, equipped with several streamwise and spanwise surface pressure microphones, has been designed and built. Flow and noise measurements have been carried out for a variety of surface treatments, with different geometrical patterns and dimensions. The flow behavior downstream of the surface treatment is also studied by employing a single probe hotwire anemometer. Results have shown that the use of such surface treatments can lead to around 8 dB reduction of the surface pressure fluctuations near the trailing edge. More importantly, it has been observed that the spanwise coherence can be significantly reduced over a wide range of frequencies, implying that the large coherent turbulent structures have been successfully removed from the boundary layer. Furthermore, the unsteady surface pressure and boundary layer velocity cross-correlation studies have shown that the correlation between the turbulent structures within the outer region of the boundary layer and the unsteady surface pressure exerted on the surface can be significantly reduced by using treatments with height of only 10% of the boundary layer thickness.
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