Numerical and Experimental Studies of Transition in Three-Dimensional Boundary Layers

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Support is provided for a combined numerical (super-computer) and experimental study of instability and transition to turbulence in the KEB class of 3-d boundary layers; the vonKarman-Ekman-Bodewadt layers. In particular, we emphasize the roll of free-stream disturbances and the excitation of the Type II instability, which has received little or no attention in previopus studies, and the different routes to transition dependent upon the relative amplitudes of the Type I and Type II unstable vortices that are known to occur in thes layers. These studies should be viewed as generic research, i.e. having application to a wide variety of problems that occur throughout mechanical, chemical, and civil and aerospace engineering. The results of a successful program of research will provide the background information for understanding transition to turbulence in a broad class of 3-d boundary layers. Three-dimensional boundary layers occur over swept-back airfoils, in the flow over and around vehicles of all sorts, in rotating machinery (fans, pumps, turbines, etc.), on the noses of rotating projectiles, incurved pipes, river bends, and planetary boundary layers. Transitition to turbulenace in these layers is important in enginerring design because it affects stresses, vibrations, nois, lift, heat transfer, ablation, etc.