A Study of Engineering Application of Pulsed Vortex Generator Jet

点击翻译按钮获取中文摘要

The general goal of the present study is to construct the closed loop control system of the reattachment process in a backward facing step flow by a row of the pulsed vortex generator jets. The step height is 40 mm. An expansion ratio of the test section height to the step height is 1.5. The step height Reynolds number is 2.7×10^4. The vortex generator jets are injected through a row of the 2 mm diameter injection holes. A micro wall flow sensor, which can detect near-wall flow reversal with a frequency response up to 500 Hz, measures time fraction of forward and backward flow. The reattachment line is almost parallel to the span-wise direction in the range of the hole pitch ratio of 10 to 20, although the discrete disturbance by jet injection is provided at the step. The reattachment length is decreased linearly up to the velocity ratio of 6. This means that the velocity ratio is one of the most effective manipulated variables in the control system of the reattachment process. The wall static pressure in the reattachment region is selected as the control feedback signal and the velocity ratio is used as the manipulated variable in the control system. The faster response of the system with the time constant of an order of 0.1 second is obtained. As a result, the present system can be employed in the engineering application as the effective control system for flow separation.