Investigation on the internal flow of ventilated partial cavity

Abstract

This study presents investigations on the internal flow behaviors and mechanisms of the ventilated partial cavity created by air ventilation behind a backward-facing step. Both planar particle image velocimetry experiments and numerical simulations have been conducted over a range of freestream velocities (U∞) for varying ventilation rates (QAs). The experimental and numerical internal flows are reasonably concordance, revealing three distinct internal flow regions: the ventilation region, the entrained internal boundary layer region, and the reversed region sandwiched in-between. The three-dimensional internal flow structures and the internal pressure gradients are numerically revealed. The internal recirculation vortex in the ventilation region is found to be induced by the stream-wise adverse pressure gradients, while the transverse airflow near the closure of the cavity is attributed to the presentence of the span-wise pressure gradient. Based on the internal velocity and air flux profiles, and the corresponding internal boundary layer thickness, the entrained and reversed air fluxes are revealed to initially increase, attain a maximum, and then decrease along the cavity. For the increment of U∞, both entrained and reversed air fluxes increase. For the increment of QAs, the entrained air flux rises, while the reversed air flux declines. Such feature is further verified and explained by applying the Couette flow model with adverse pressure gradients, which provides a reasonable estimation of internal flow profiles and offers a theoretical explanation on the change of internal air flux due to the variation of U∞ and QAs.