Aerodynamic control of bluff body noise

The main aim of this study was to investigate noise reduction techniques for bluff body noise. Three methods were investigated, using a splitter plate on a fairing- strut configuration, applying flow control to the surface of a fairing and fitting a splitter plate behind a isolated bluff body. Aerodynamic tests were performed in wind tunnel facilities using particle image velocimetry (PIV), hotwire anemometry, pressure sensors and a force balance. Acoustic tests using a microphone array, on-surface microphones and freefield mi- crophones were performed to investigate the noise generated by the models. The splitter plate fitted to the fairing-strut configuration was found to be dominated by large scale vortex shedding. The addition of the splitter plate blocked the interaction between the two opposing shear layers aft of the shell's trailing edge thereby reducing their interaction with the downstream strut. Broadband noise reductions were observed as well as reduction in the noise levels of the peaks asso- ciated with the shedding. Applying flow control showed noise reductions for both cases when suction and blowing were applied. These reductions were observed at the lower tested Reynolds numbers (ReDshell = 1.75 x 105), at higher Reynolds numbers (ReDshell = 3.5 x 105) the noise reductions decreased when compared to the baseline case. The splitter plate fitted behind an isolated bluff body modified the wake, decreasing shedding frequency and drag with an increase in the splitter plate length. Broadband noise reductions were observed with all three splitter plate lengths and the tonal peak of the vortex shedding noise was suppressed. The study shed light on the possibility of achieving noise reductions using the three methods. However more research is required to apply these findings on a landing gear.