Decay of streamwise vorticity downstream of a three-dimensional protuberance

Abstract

Streamwise vortices generated in boundary layers are known to persist for hundreds of boundary-layer thicknesses. This remarkable property is the main topic of this paper. The particular case of the flowfield generated by a three-dimensional protuberance immersed in a flat plate boundary layer is studied using numerical modeling. Experimental measurements in a downstream crossflow plane are used to construct initial data for a marching calculation using the boundary-layer and boundary-region approximations; the latter includes crossflow diffusion terms. The former fails to predict the flowfield, but results from the latter agree qualitatively with aspects of the flowfield determined from the measurements of Tani et al. and are also in fair quantitative agreement.