Bifurcation phenomena in the flow through a sudden expansion in a circular pipe

We report the results of an experimental investigation into bifurcation phenomena in laminar and time-dependent flows through a sudden expansion in a circular pipe. The flow state was investigated using high resolution magnetic resonance imaging techniques which have enabled us to identify important qualitative features in the flow field and make quantitative estimates of the velocity distributions. Using these techniques we have uncovered evidence for a steady symmetry breaking bifurcation at a critical value of the Reynolds number. The asymmetric steady state which arises at the bifurcation point eventually gives way to time dependence in the form of bursts of periodic motion with further increase in flow rate. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3065482]