受电弓是露置于高速列车顶部的重要受流装置,其所产生的气动噪声是高速列车的主要噪声源之一.为了降低受电弓所产生的气动噪声,采用椭圆截面直杆件和椭圆截面纵向扭转杆件两种方案替代原有上下臂杆的圆形截面直杆件,基于大涡模拟(large eddy simulation,LES)结合Ffowcs Williams and Hawkings(FW-H)声类比的方法分析流场特征与气动噪声辐射,研究新型受电弓杆件对流场及近、远场气动噪声特性的影响.研究结果表明:在不同列车速度下,与圆形截面杆件相比,椭圆截面纵向扭转杆件受电弓在近、远场辐射的气动噪声有所减弱,具有一定降噪效果;当列车速度为300 km/h时,椭圆截面纵向扭转杆件受电弓远场25 m处声压级最大值可降低约4.3 dB(A),降幅约4.4%;当列车速度为400 km/h时,其近场7.5 m处声压级最大值可降低约5 dB(A),降幅约5.5%.
Large eddy simulation of aerodynamic noise reduction of upper and lower arms of high-speed train pantographs
As an important current receiving device exposed on the top of a high-speed train,the pantograph radiates aerodynamic noise and thus has become one of the main noise sources of high-speed trains.In order to suppress the aerodynamic noise radiated from pantograph and its components,large eddy simulation(LES)of air flow was carried out around a simplified on-roof-pantograph via replacing original circular cross-section straight rods of the upper and lower arms with elliptical cross-section straight rods and elliptical cross-section longitudinal torsion rods,respectively,combined with the sound analogues of Ffowcs Williams and Hawkings(FW-H).The flow characteristics and aerodynamic noise radiation were analyzed to study the effect of the new type of pantograph arms on the flow and the aerodynamic noise characteristics in the near and far fields.The results show that the aerodynamic noise in the near and far fields radiated by pantographs with elliptical cross-section longitudinal torsion arms appears to be weaker at different speeds of high-speed train,implying some kind of noise reduction effect.Specifically,when the speed is 300 km/h,the peak of sound pressure level at 25 m in the far field can be reduced by about 4.3 dB(A),or about 4.4%.When the speed is 400 km/h,the peak of sound pressure level at 7.5 m in the near field can be reduced by about 5 dB(A),or about 5.5%.
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