Boundary layer flow interaction with porous surfaces

The present study demonstrates the mechanisms of flow interaction and sound generation with porous surface as a passive flow control method for different configurations. The flow interaction characteristics have been examined using a flat plate equipped with several surface pressure transducers. To reveal the effect of porosity, four types of porous materials with different porosities and permeability constants were tested. To better understand the effect of flow behaviour over porous surfaces, measurements have been conducted for the boundary layer growth and surface pressure fluctuations, before, over and after the porous section. Velocity measurements have also been performed to investigate the flow pattern and the energy content of the turbulent structure within the boundary layer. Results have shown that the porous surface treatment changes the boundary layer profile and significantly reduces the energy content of the velocity fluctuations within the boundary layer. It has been observed that the porous surface also causes significant reduction in the surface pressure fluctuations of about 6 dB over the high-frequency range. The porous treatment also leads to a noticeable reduction in the coherence and the length-scales of the spanwise flow structures. These results are essential for understanding the flow-porous interaction in real world applications.