The use of surface treatments as a passive flow control method for trailing edge noise reduction is considered in this paper. In order to investigate the effects of different types of surface treatments on surface pressure fluctuations, eddy convection velocity and spanwise length scale, a long flat-plate model, equipped with several streamwise and spanwise surface pressure microphones has been designed and built. Measurements have been carried out for a variety of 2D and 3D surface treatments. The flow behavior downstream of the surface treatments is also studied by employing a single probe hotwire anemometer. Results indicated that the use of finlets with coarse spacing leads to a favorable reduction in PSD at mid to high frequencies and an undesirable increase in spanwise length scale. In the case of finlets with fine spacing, the high frequency pressure fluctuations have been effectively suppressed and the spanwise length-scale has been reduced, but with a penalty of low to mid frequency surface pressure elevation. Furthermore, it is found that the ratio of the finlets spacing to the boundary layer thickness is a critical parameter for achieving maximum surface pressure PSD reduction and the finlets spacing should be in the order of the boundary layer inner region. It has also been shown that the proposed novel 3D surface treatments have better aeroacoustic performance than the standard 2D ones in terms of the reduction in the surface pressure power spectral density, the longitudinal and lateral coherence and eddy convection velocity.
|Title of host publication||23rd AIAA/CEAS Aeroacoustics Conference|
|Publisher||American Institute of Aeronautics and Astronautics Inc. (AIAA)|
|Number of pages||17|
|Publication status||Published - 5 Jun 2017|