Experimental Study On Flow And Noise Control Of Carrier Aircraft Wake Impinging On Jet Blast Deflector

There are usually deflectors behind the carrier-based aircraft for short take-off and landing on the aircraft carrier deck,which can not only increase the utilization rate of deck space,but also prevent the high-speed,high-temperature and high-pressure wake generated by the carrier-based aircraft from threatening the safety of personnel and materials behind the aircraft.However,the existence of the deflector significantly increases the noise radiation,which seriously threatens the physical and mental health of the ground crew and the safety of the precision instruments on the aircraft carrier deck.In order to optimize the noise environment of the aircraft carrier deck and ensure the safe take-off of the carrier-based aircraft,it is urgent to carry out research on the noise suppression of the carrier-based aircraft wake impact deflector.This problem can be simplified to the problem of supersonic jet impinging on the inclined plate.In this paper,combined with high-frequency PIV,far-field noise arc array experiment and numerical simulation,the coupling structure of the flow field and sound field of the jet impinging on the inclined plate is deeply studied.The noise radiation characteristics and the flow mechanism generated by the noise source are analyzed under different parameters such as nozzle-inclined plate impact distance,nozzle outlet pressure ratio,and inclined plate deflection angle,so as to establish an engineering-applicable impact jet noise prediction model.The micro-modification design of the deflector based on the bionic surface texture can suppress the impacting jet noise of the wake of the carrier aircraft and precisely control the scattering direction of the impacting wake without affecting the performance of the deflector.The research results will provide theoretical guidance and technical support for the reduction of aircraft carrier deck noise and the precise control of the wake of the aircraft carrier-deflector in the future.The main research contents are as follows:Through experiments and numerical methods,the sound field characteristics of the jet impinging on the inclined plate and the flow mechanism of the noise source are deeply analyzed.The specific research contents include: nozzle-inclined plate impact distance,nozzle outlet pressure ratio,inclined plate deflection angle and other working parameters Influence on the sound field characteristics and flow field structure of the impinging jet;the variation law of the internal fine structure of the stagnant bubble in the impingement area of the jet under different working parameters.Based on the in-depth study of the flow field structure,the flow mechanism of noise generation is analyzed,and the correlation mechanism between the working parameters,the flow field structure and the sound field is clarified.The parametric research method is used to summarize the influence of the flow field parameters on the regularity of its position.Based on the in-depth study of the flow field structure,the experiment finds the location of the "quiet zone".It can be seen that when the impact distance L=4.0d～4.4d,the total sound pressure level of the impacting jet noise is relatively small,which is called the "quiet zone".And a prediction model based on semi-empirical formula is established to guide the selection of the relative position of the carrier-based aircraft/deflector in engineering practice.The biomimetic noise reduction surface fence structure developed by imitating the body surface morphological characteristics of organisms with noise reduction function provides an idea for the micro-modification design of the surface of the deflector.Within the allowable range of surface flatness,the small-scale groove structure is used to realize the flow control of the impinging jet wake,so that the jet flow after impingement changes from scattered to upward guidance.In addition,considering the noise suppression of impingement jet and the effect of wake control,a small-scale groove structure with groove width S=4 mm and groove depth H=5 mm is selected for the optimal orbit and low-noise impingement swash plate configuration in this paper.To sum up,this paper focuses on high-frequency PIV and microphone arc array experiments,combined with high-precision numerical simulation methods,and conducts an in-depth analysis of the flow field and sound field characteristics of the jet impinging on the inclined plate under different parameters.Flow mechanism;establish a semi-empirical formula based on experimental data to determine the position of the "quiet zone",thereby guiding the selection of the relative position of the carrier-based aircraft and the deflector in engineering practice;based on the bionic surface texture to micro-modify the surface of the inclined plate to reduce noise The method is used to realize the wake control and noise suppression of the impinging jet.