The Use of Micro-jets for Airfoil Self-noise Control

The current work is an experimental investigation on the use of open-loop flow control techniques to reduce trailing edge noise of a flat plate. An array of inclined transverse jet nozzles is placed upstream of the trailing edge, with the aim of controlling the hydrodynamic pressure field associated with the boundary layer. The turbulence statistics downstream of the flow control section were measured with the use of hot-wire anemometry, while the simultaneous measurement of the surface pressure fluctuations was performed with flush mounted microphones. It is shown that the proposed flow control method leads to a reduction of the energy content of the surface pressure fluctuations in the region of low and mid frequencies. The spanwise correlation length of the turbulent structures near the trailing edge is also observed to decrease as a consequence of using multiple jet injections. In general, results have shown that the proposed flow control technique can alter theboundary layer structure, and it has the potentials to reduce far-field trailing edge noise.