Influence of base jets on trailing edge bluntness noise generation

This study investigates the influence of air blowing on the aerodynamic noise generatedby a flat plate with a blunt trailing edge. The uniform blowing was applied through evenlyspaced holes along the span at the base of the flat plate. Acoustic pressure measurementswere conducted in an anechoic wind tunnel using a free-field microphone at Reynolds numbersranging from2.8×105to6.5×105. Particle image velocimetry measurements were performedto obtain time-resolved evolution and statistics of the flow velocity field, providing a detailedunderstanding of the noise reduction mechanisms. The results demonstrated that air blowingeffectively reduces both the amplitude and bandwidth of tonal and broadband noise within alimited frequency range. This phenomenon was attributed to the stabilisation of separatedshear layers over a longer distance by air blowing and a decrease in turbulent kinetic energyin the near-wake region. It was shown that air blowing effectively suppresses the tonal peakof vertical velocity fluctuations at the end of the vortex formation region. It was pronouncedat the fundamental vortex shedding frequency, without weakening the spanwise correlationand convective velocity of the large-scale vortex structures, which is the primary mechanismresponsible for tonal noise reduction.