Pulsating jet control for manipulating the separation bubble behind the fence

Abstract

An optimization study of a pulsating jet was performed to manipulate the separation bubble behind the fence. The experiments were carried out in a circulating water channel and the vertical fence was submerged in the turbulent boundary layer. The parameters used for controlling the pulsating jet included the frequency, speed and velocity profile of jet, and the geometries including angle and location of nozzle. In addition, we investigated the effect of upstream boundary layer changed by continuous suction in front of the jet nozzle. Each test case was divided into 20 phases and phase-averaged DPIV method was applied to measure the velocity field. From the results, the main mechanism of reduction of bubble length was the vortex shedding from the recirculating region. The specific jet condition and nozzle geometries which were effective to reduce the separation bubble behind the fence were found.