Prediction of the Effects of Longitudinal Wall Curvature and System Rotation on Turbulent Boundary Layers.

摘要

Two-dimensional (x,y plane) turbulent boundary layers on walls with convex curvature in the mean flow (x) direction have lower turbulence stress levels than equivalent layers on flat walls. As a result,convex wall flows have higher shape factors H,lower skin friction coefficients (C sub f) and lower momentum-thickness Reynolds numbers (Re sub theta). Opposite effects are seen on concave walls. Flows over flat walls which rotate at a steady rate,as a system,about a spanwise (z) axis have been shown to have similar effects. A calculation method utilizing a simple mixing-length correction factor is developed and is seen to predict the effects of weak curvature and slow rotation on H, (C sub f),and (Re sub theta) reasonably well. The predicted effects of curvature and rotation are shown to be particularly strong in flows with adverse pressure gradients.