Infuence Of Free-Stream Turbulence On Boundary Layers
National Aeronautics and Space Administration (NASA)
The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent boundary layers is presented for the cases of zero and mild adverse pressure gradients. With free- stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free-stream, both of which act to improve the transmission of momentum from the free-stream to the boundary layers.
Hoffman, J. A.; Kassir, S. M.; and Larwood, Scott M., "Infuence Of Free-Stream Turbulence On Boundary Layers" (1992). School of Engineering and Computer Science Faculty Reports. 7.