Unsteady, Separated Laminar Flow in Non-Uniform Vessels
Regions of flow separation appear to be important sites for athero-genesis. Here we show that flow unsteadiness, even at low frequencies, has a significant effect on the location of and wall shear stress in separated eddies. Experimental and computational results are presented for (i) flow past a time-dependent, asymmetric indentation in a two-dimensional channel, and (ii) oscillatory flow through a fixed expansion. Trains of vorticity waves are observed downstream of the indentation or expansion, each wave associated with a separated eddy which somtimes itself divides into two. The wall shear stress in the eddies is much larger than in steady or parallel flow. Also, in each case the flow eventually becomes three-dimensional.
KeywordsWall Shear Stress Strouhal Number Oscillatory Flow Plane Wall Flow Unsteadiness
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