Study of bifurcation flow phenomena in symmetric sudden expansions

Incompressible flow in sudden expansions is one of the classical examples in the field of separated flows. Study of such flows can improve our understanding of the separation mechanism in both laminar and turbulent flow regimes. At certain Reynolds numbers these flows present instabilities which may lead to bifucation, unsteadiness, and chaos. The importance of investigating nonlinear bifurcation phenomena in fluid mechanics is in enabling a clearer understanding of hydrodynamic stability and the mechanism of laminar-to-turbulent flow transition. Furthermore, flow through sudden expansions can be encountered in a variety of physiological flows, e.g. flow through prosthetic devices and aortic stenoses, as well as, in various engineering applications, such as, fluid delivery systems and heat exchangers. The phenomenon of asymmetric separation in sudden-expansion flows has been discussed in several research works mostly of which are experimental (Durst et al., 1993) but some numerical (Shapire et al., 1990). However, there are inconsistencies in the results of these research efforts regarding the critical Reynolds number for the symmetry-breaking bifurcation. The objective of the present study is to investigate Reynolds number effects and elucidate open questions on separated flows in a plane sudden-expansion with expansion ratio 1 : 2.