The present study investigates the effect of deceleration on the threshold of transition from asymmetry to symmetry with respect to the flow through a symmetric 1:3 sudden expansion. A finite volume computational fluid dynamics code is utilised for simulating the unsteady decelerating flow for various deceleration rates in order to define the critical Reynolds number at which the onset takes place for each case. Results show that higher deceleration rates lead to lower critical Reynolds numbers and furthermore that this, in conjunction with existing studies that show that for steady symmetrically-expanding flows, higher expansion ratios lead to lower critical Reynolds numbers, underlines the flow deceleration effect as the key factor to the onset of asymmetry.

computational fluid dynamics, symmetry-breaking.