Experimental Investigation of Suction on the Boundary Layer Flow Over a Rotating Disk

An experiment was performed to study the effects of applying a uniform normal flow of suction to the surface of a flat disk rotating at constant speed. Previous research has shown that the absolute instability of Type I crossflow modes can initiate transition to turbulence in the boundary layer flow over a rotating disk. This same crossflow instability is evident in boundary layer flow over the leading edge of a swept wing. Thus, an understanding of the transition to turbulence in flow on the rotating disk can help in future research and development of laminar flow control on swept wings. For this experiment, a new disk was designed that applied suction through two different surfaces. The basic flow over this disk was documented for each surface, both with and without suction, by acquiring hot-wire velocity measurements at various radial and wall-normal positions throughout the boundary layer. These results were compared to see the effect suction had on the location of the boundary layer's transition to turbulence, as well as the wall-normal and radial growth of velocity fluctuations caused by Type I stationary modes. The amplitudes and frequencies of these modes were also examined.