A Study of Engineering Application of Pulsed Vortex Generator Jet

本研究的总体目标是通过一排脉冲涡旋产生器射流构建后向台阶流再附着过程的闭环控制系统。台阶高度为40毫米。测试段高度与台阶高度的膨胀比为1.5。台阶高度雷诺数为2.7×104。涡流发生器射流通过一排直径为2 mm的喷口喷出。一种微型壁面流量传感器，可以检测到频率响应高达500赫兹的近壁流动反转，测量正向和反向流动的时间分数。在孔距比为10~20的范围内，虽然在台阶上提供了射流注入的离散扰动，但再附着线几乎平行于跨距方向。再附着长度在速比为6时呈线性减小，这意味着速比是再附着过程控制系统中最有效的操纵变量之一。在控制系统中，选择附着区的壁面静压作为控制反馈信号，以速比作为操纵变量。对于时间常数为0.1秒量级的系统，获得了较快的响应速度。结果表明，该系统可作为一种有效的气流分离控制系统应用于工程应用。

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.