Three-dimensional flow in a lid-driven cavity with width-to-height ratio of 1.6

The flow in a lid-driven cavity with width-to-height ratio of 1.6 is investigated numerically and experimentally. Experimental investigation use an apparatus with a spanwise length-to-height ratio of $Uplambda = 10.85.$ Λ = 10.85 . Increasing the Reynolds number, we experimentally find a gradual change from the quasi-two-dimensional basic flow to a three-dimensional flow pattern. The three-dimensional flow has a significant amplitude at considerably low Reynolds numbers. Streak-line photographs and PIV vector maps are presented to illustrate the structure of the finite-amplitude flow pattern. The smooth transition is in contrast to the linear instability predicted by a linear-stability analysis for a cavity with infinite span. LDV measurements confirm the absence of a distinct threshold Reynolds number and indicate an imperfect bifurcation. The deviations between experimental observations and numerical critical Reynolds number for infinite span are explained by conducting three-dimensional simulations for a finite-span geometry. A good agreement between experimental and numerical simulation is obtained. The numerical and experimental data lead to the conjecture of a premature onset of the three-dimensional flow caused by strong secondary flows which are induced by the cavity end walls. Nevertheless, the flow structure in the finite-span cavity carries the same characteristic signatures as the nonlinear flow in the corresponding infinite-length cavity. We conclude that the observed flow can be identified as the continuation of the normal mode C _e ⁴ earlier identified in a linear-stability analysis.