Experimental And Numerical Study On Aerodynamic Noise Control Of High-speed Train Pantograph Using Bionic Method

With the improvement of train speed, the noise has become serious problemrestricting the further development of the high-speed train. As a current collecting deviceplaced on top of the high-speed train, the pantograph can produce a strong aerodynamicnoise at high speed. To reduce the aerodynamic noise of high-speed train pantograph hasbecome an important subject for the relevant companies and research institutions. Rodsare important components of the pantograph, which are seclected to be the research objectin this paper. Inspired by serrations at the leading edge of the owl’s wing, we explored thebionic control methods and mechanisms in aerodynamic noise of the cylindrical rods andthe four-prismatic rods. An experimental application research of high-speed trainpantograph was carried out as well.On the basis of the bionic research by our research team, the birds with low noiseflight capabilities such as long-eared owl, short-eared owl, etc, we carried out a drag andnoise reduction research regarding the cylindrical rods and the four-prismatic rods usingbionic flow control methd. O-ring and helical hoop are arranged on cylindrical rod surface,and drilling holes on the four-prismatic rod. comparison of fluctuating pressure andaerodynamic noise between the smooth cylinder and the bionic cylinder at speed of14m/s,28m/s,42m/s and56m/s was conducted through the experiments using fluctuating pressuremeasurement system and microphone array noise identification system in FD-09low-speed wind tunnel of China Aerospace Aerodynamics Research Institute.Aerodynamic noise measurement results show that the sound pressure level (SPL) ofthe O-ring cylinder model and the helical hoop cylinder model is significantly lower thanthat of the smooth cylinder both in the low and high frequency regions at speed of14m/s.At speed of28m/s, the SPL of the O-ring cylinder is significantly lower than that of thesmooth cylinder both in low and high frequency regions, and for the helical hoop cylinder,it’s significantly lower from1602Hz to2500Hz. At speed of42m/s, the SPL of the O-ringcylinder is significantly lower than that of the smooth cylinder in low frequency region,but it’s not obvious in other frequency regions. The SPL of the helical hoop cylinder issignificantly lower than that of the smooth cylinder only at about2500Hz. At speed of56m/s, the SPL of the O-ring cylinder is slightly lower than that of the smooth cylinder below250Hz and significantly lower in the high frequency region. The SPL of the helicalhoop cylinder is significantly reduced almost over the whole frequency band.The pulsating pressure measurement results show that the pulsdting pressure of theO-ring cylinder and the helical hoop cylinder are significantly reduced at8test points at14m/s, the maximum reduction of the O-ring cylinder is10.04dB, and that is13.04dBfor the helical hoop cylinder compared with the smooth cylinder. At28m/s, the maximumreduction of the O-ring cylinder and the helical hoop cylinder are2.58dB and4.93dB. At42m/s, the O-ring cylinder and the helical hoop cylinder reduced maximally2.04dB and2.21dB. At56m/s, the O-ring cylinder and the helical hoop cylinder reduced maximally17.13dB and17.44dB compared with smooth cylinder.A numerical investigation on aerodynamics and aeroacoustics performance of thesmooth rod and the bionic rod at uniform velocity of56m/s and106m/s is conductedthrough simulations with Large Eddy Simulation method and FW-H equation. Comparedwith the smooth cylinder, the total SPL of the O-ring cylinder and the helical hoopcylinder are all significantly lower, the fluctuating amplitude of the lift coefficient and thesound pressure are all reduced. Furthermore, the fluctuating frequencies of lift coefficientare all significantly lower than that of the smooth cylinder. The comparesion of pressuredrag results shows that the proportion of pressure drag in total resistance of the O-ringcylinder and the helical hoop cylinder are all lower than that of the smooth cylinder. Thetotal resistance of the the O-ring cylinder and the helical hoop cylinder are all lower thanthat of the smooth cylinder, except the total resistance of the O-ring cylinder is higher thanthat of the smooth cylinder at56m/s. From the flow field comparison we can see theboundary layer separation point of the O-ring cylinder and the helical hoop cylindersignificantly move backward, and the wake vortex scale are smaller than that of thesmooth cylinder. The process of separated shear layer transiting to turbulence is effectivelyrestrained, and the fluctuations amplitude of wake vortex is significantly reduced.The total SPL at two wind conditions of the punching four-prismatic rod weresignificantly lower than the smooth four-prism rod model. The total resistance of thepunching four-prismatic rod is significantly lower than the smooth four-prismatic rod, andthe proportion of pressure drag in total resistance is also lower. It is can be seen thethrough-hole units can reduce the aerodynamic drag of the four-prismatic rod significantly,and effectively balance the lift fluctuations as well. The wake flow is stable, and also thetransition from laminar to turbulent flow is delayed with the reduction of the wake vortexshedding frequency results in the aerodynamic noise.The noise reduction technology of bionic flow control was used to reduce the noise of single-arm pantograph. Aerodynamic noise source identification contours at wind speedof56m/s,1/3octave and center frequency of800Hz indicated that the noise level andradiation scope at bionic pantograph head are all reduced, the distribution of noise energyat arm also become uniform. The disturbance to flow field for closed pantograph issignificantly weaker than the opened pantograph, correspondingly the radiation scope ofnoise sources also significantly narrowed, and the sound pressure level also is significantlyreduced.