Flow Separation Opposite A Side Branch

The flow of a fluid along a tube becomes distinctly three-dimensional in the vicinity of a side branch which carries away a fraction of the total flow. In some circumstances the flow on the straight tube wall separates opposite the side branch with the formation of a separation bubble or horseshoe vortex according to various observers. Here it is proposed that the conditions for this flow separation can be predicted by adapting the analysis known to predict separation in divergent ducts bearing two-dimensional flows. The prediction of this adapted analysis is examined experimentally and is shown to hold in a range of Reynolds numbers of physiological interest for branching of systemic arteries.