Effects of Pressure Gradients on Turbulent Boundary Layer Flow Over a Flat Plate with Riblets
AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
Pagination or Media Count:
The Air Force Institute of Technology Boundary Layer Research Facility test section was modified to create controlled non-zero streamwise pressure gradients. The capability of the modified facility to reproduce theoretical laminar boundary layer velocity profiles and to create a self-preserving flow with an adverse streamwise pressure gradient was verified with three-dimensional laser Doppler anemometry. The effects of streamwise adverse and favorable pressure gradients on turbulent boundary layer flow characteristics velocity profiles, turbulence and skin friction and vortex formation over a flat plate with riblets at low speed U 5 mIs were studied. Normal and spanwise velocity profiles for both pressure gradients showed the presence of paired counter-rotating vortices nested within the riblet valleys. These flow structures increased drag and significantly altered near-wall flow compared to a smooth plate turbulent boundary layer. The adverse pressure gradient tended to degrade these vortices as the flow progressed.
- Fluid Mechanics