Drag Reduction Of Flat-plate Turbulent Boundary Layer Using Synthetic Jet Actuator Based On PD Control

In the field of engineering,the effect of friction drag can be seen everywhere.Airplanes and submarines are often able to greatly reduce fuel consumption by reducing friction drag.With the development of the times,the global warming problem is imminent which is connected to excess carbon dioxide(CO2)emission,and the reduction of CO2 emission can be significantly reduced through active control.Therefore,the boundary layer drag reduction not only has a high economic value,but also has a very high practical value in the field of environmental protection.Friction drag is predominantly depended on the boundary layer.With the discovery of the near-wall coherence structure of the boundary layer,many domestic and overseas scholars are motivated to do research in boundary layer drag reduction in unprecedented enthusiasm.Various countries have also vigorously promoted the project of drag reduction of boundary layer.Drag reduction through active control is of loads of advantages,such as high drag reduction rate,are expected to be the outstanding method to solve problem of drag reduction.This project is based on the synthetic jet technology to design the actuator for the turbulent boundary layer drag reduction.With periodical vibration of piezo-electric ceramic membrane within the cavity,a periodically varying synthetic jet is formed outside the exit slit of the cavity.The zero mass jet outputs momentum but the outward mass is zero,and has advantages of low energy consumption and simple structure.The synthetic jet actuator based on the piezoelectric ceramic membrane has the advantages of strong controllability and low cost.Based on the above considerations,the synthetic jet actuator is used to control the drag reduction of the flat-plate turbulent boundary layer.This paper studies the various characteristics of the synthetic jet actuator,including voltage characteristics,frequency characteristics,spectrums,exit velocity,and derives the theoretical formula of the exit velocity.Two methods are used to verify that the mass of the synthetic jet is zero.The formation of synthetic jet is revealed according to the Particle Image Velocimetry experiment.In this experiment,open-loop control and feedforward PD control experiments were performed and compared.The open loop control structure is simple and has achieved a drag reduction of 19.11%.Based on the open-loop control,this experiment carried out the experiment of feedforward PD control,calculated the delay time in the system,and established the feedforward prediction function.After that,the experiment of feedforward PD control achieved the control effect of the maximum drag reduction of 20.42%,which was 1.31% more than the open loop control and greatly reduced the energy consumption and consequently improved the control efficiency.