Turbulence Augmentation over a Bristled Shark Skin Model

Experiments were conducted to discern the turbulence augmentation achieved over a bristled shark skin model embedded inside a turbulent boundary layer. It is hypothesized that shark scales are passively bristled by the flow in regions where incipient separation is present. The formation of embedded vortices within the model leads to the presence of partial slip velocities adjacent to the main boundary layer flow which range from 5 – 30% of the freestream velocity. The turbulence levels in the boundary layer are increased as measured by the increase in Re stress levels, which also leads to the high partial slip velocities via mixing in and out of the cavities. It is hypothesized that that positive effect of an increase in momentum adjacent to the surface will prevent local flow reversal and global flow separation. Results suggest that the negative aspects of increased overall drag, as evidenced in the boundary layer profiles, would be minimized if only localized bristling were to occur thereby minimizing the surface area of the bristled microgeometry.