Distributed Velocity Negative Feedback Control Study Of Thin Plate Acoustic Vibration Response Under Turbulent Boundary Layer Excitation

Among the structural noise induced by pulsating pressure in turbulent boundary layer,the control of low-frequency radiated noise has been an important research direction.And for the control of low-frequency radiated noise,distributed velocity negative feedback control is a well-established method.Therefore,this paper investigates the acoustic vibration response of a thin plate under pulsating pressure in the turbulent boundary layer based on distributed velocity negative feedback control.In the study,the display expression of active damping for distributed negative velocity feedback control is given based on the modal expansion method,revealing the damping mechanism of active control,solving the problem of time-consuming calculation by the traditional element-based model,and laying the foundation for the optimization of the position and number of feedback control units on larger structures.The main research contents and innovations of this paper are as follows.(1)A theoretical model for distributed negative feedback control of the curved plate velocity under pulsating pressure in the turbulent boundary layer is developed.The effects of feedback control unit distribution,plate thickness and curvature on kinetic energy and radiated acoustic power are discussed.The results show that the control of the low-order high-radiation modes of the curved plate under turbulent boundary layer excitation is crucial,since these modes dominate the acoustic radiation of the plate.However,the control of these modes is sensitive to the ratio of the stiffness associated with the film force to the stiffness associated with the bending force.The control of distributed negative velocity feedback is less effective when the curved plate thickness is thinner and the radius of curvature is smaller.(2)The response and acoustic radiation of the thin plate under the joint action of turbulent boundary layer and distributed velocity feedback control are derived using the modal expansion method,and the displayed expressions for the active damping of the feedback control are given.The effects of the arrangement and number of distributed velocity feedback control units on the modal damping are discussed,as well as the effects of the arrangement of the feedback control units,the free flow velocity,and the thickness of the plate on the kinetic energy and the radiated acoustic power.The numerical analysis results show that the number and location of the feedback control unit have a significant effect on the control effect,and the arrangement of the feedback control unit along the helix can significantly broaden the control band.And with the same gain,the control effect of the feedback control unit becomes worse with the increase of the thickness of the thin plate.(3)The modal average acoustic radiation efficiency of the thin plate under the combined effect of turbulent boundary layer and distributed velocity negative feedback was calculated using the modal expansion method.The effects of free flow velocity,structural damping and thickness on the mode-averaged acoustic radiation efficiency of thin plates under turbulent boundary layer excitation are discussed.The results show that the structural damping can significantly improve the acoustic radiation efficiency of the plate,and the flow rate and thickness have a greater effect on the acoustic radiation efficiency in the middle and high frequency bands.The effects of the arrangement of the control unit,flow rate and thickness on the acoustic radiation efficiency are also discussed.The results show that the arrangement of the feedback control unit along the helix leads to a significant increase in the acoustic radiation efficiency in the middle and high frequency bands of the thin plate,and that the increase in plate thickness suppresses the mode-averaged acoustic radiation efficiency of the thin plate under distributed velocity negative feedback control.