Active Control Study Of Backward Step Flow

There is a common phenomenon that boundary layer separated from solid wall in flow field of aircraft trailing edge and industrial production. There is often a large shear rate in the separation area, where the large-scale vortex structures emerge and develop. These vortex structures have rich pulsating kinetic energy, which can transfer momentum and heat effectively. When these vortex structures attached to the solid wall again, the Fluctuating pressure and convective heat transfer intensity of the attaching area will increase. To affect the development of large-scale vortex structures in the shear layer by instrument of control is large significance to reduce aircraft drag, protect the safety of industrial production, and improve energy efficiency.This article discusses several control methods of the development of large-scale vortex structures in the shear layer, including open-loop and closed-loop method. And a design of a back-step flow bench to study the comprehensive experimental open-loop control of this representative separated flow.In order to get the separated flow characteristics under open-loop active controller. This article uses particle image velocity system to get the information of the macro velocity distribution in the flow field at a certain time.In order to lay the foundation for the closed-loop control experiments, this article also contains the the design of some experimental instruments such as multi-channel pressure sensor, hot-wire anemometer and tracer particles generator that need to use.At the signal processing,this article uses the phase-mean method to process the large amounts of data from particle image velocity system, thus, the velocity distribution of the flow field at the different frequency of the controller has been acquired. Thus, the difference between the physical phenomena that under different actuator’s frequency has been found. Give an reasonable explanation for the difference between the experimental results and numerical analysis, and get the transfer function between input and output. This study will be lots of significance for the closed-loop flow control theory and engineering practice.