On the enhancement and suppression of turbulent wall pressure by the Large Eddy BreakUp devices

Abstract

An experimental study is presented on the application of Large Eddy BreakUp (LEBU) on a flat plate as an aeroacoustics noise source-targeting device to perturb the wall pressure fluctuations of a turbulent boundary layer. When interacting with a LEBU wake, the wall pressure spectra can establish a self-similar behavior against s′, which is a normalized separation distance between the LEBU's trailing edge and the targeted location for aeroacoustics noise source mitigation. It is found that s′>3 is needed to achieve an overall reduction in the wall pressure fluctuations. The fundamental mechanism by which the LEBU can reduce the wall pressure fluctuation is investigated by studying the spatio-temporal evolution of turbulent spots. When the emanated LEBU wake is interacted with the outer part of turbulent spot, the shielding effect can always inhibit the turbulent fluids ejection from the spot's leading edge. However, incursion of the high momentum fluids wall-sweeping event at the spot's trailing edge can only be effectively prevented when s′>3.