高速列车转向架区域近地空腔内复杂结构气动噪声产生机理与控制研究

The bogie region is one of the main aerodynamic noise sources of high-speed trains. Due to the influence from the three-dimensional cavity flow, the vortex shedding and the ground boundary layer, the flow and flow-induced noise developed around the bogie are complex. It was found that the dominant noise sources around the bogie areas were generated from wall pressure fluctuations whose generating mechanism and the influence factor were not clear. The vortex generating in the shear layer introduced from the bogie cavity leading edge and the vortex interactions within the bogie cavity as well as around the cavity trailing edge might produce the wall pressure fluctuations. Therefore, the theory of vortex sound will be applied to study the relations between the vortices and the wall pressure fluctuations. The acoustic analogy method using the permeable integration surfaces will be developed to investigate the key factors on generating the aerodynamic noise around the bogie areas. Based on the numerical simulations using the high-precision numerical scheme and the experimental measurements in the large low-noise anechoic wind tunnel, the research will be carried out to reveal the behaviour of the unsteady flow and the characteristics of the pressure fluctuation induced by the interaction between the various vortices and geometries of the bogie and bogie cavity. The noise generating mechanisms will be disclosed around the bogie region which can be treated as a complex structure situated within the bogie cavity in proximity to the ground. Moreover, the aerodynamic noise control methods for the bogie areas will be developed by introducing the shear layer disturbance along the bogie cavity leading edge and optimizing the configuration of the bogie cavity trailing edge.

转向架区域是高速列车气动噪声的主要声源部位之一，由于三维空腔流动、转向架涡脱落以及近地面边界层等多重效应影响，导致其内部流动及其诱发的噪声问题影响因素十分复杂。已有的研究表明转向架区域固体壁面上压力脉动是主要噪声源，但是诱发壁面压力脉动的机理和影响因素尚不明确。其中，转向架舱前缘剪切层涡流、转向架舱内的空腔涡流以及转向架尾迹涡脱落等都有可能诱导出上述壁面压力脉动。本项目设想采用涡声理论与发展基于可穿透积分面的声比拟方法，揭示转向架区域涡流与壁面压力脉动之间的关联机理和气动噪声产生的关键影响因素。项目研究中借助高精度数值模拟方法和大型声学风洞测试技术，获取详细的转向架区域非定常流动特征，阐明不同涡流结构与转向架舱以及转向架等边界干涉诱发的压力脉动特征，揭示转向架区域近地空腔内复杂结构气动噪声产生机理。在此基础上，引入流动控制方法和优化转向架舱后缘结构，开展高速列车转向架区域气动噪声控制研究。

高速铁路以其迅速高效、节能环保以及安全舒适等优越性，在世界各国得到了迅猛发展。铁路高速化已成为当今世界发展的一个重要趋势。当高速列车运行速度超过300km/h并且不断提高时，气动噪声将高于滚动噪声和牵引噪声，成为主要噪声源。本项目针对高速列车气动噪声主要声源的转向架区域，根据涡声理论和声类比方法，基于数值模拟和风洞测试研究转向架区域流动特性及其对气动噪声产生的影响，获取该区域气动噪声控制的有效措施。研究结果表明：由于转向架舱在车体侧墙与底部存在表面结构不连续，流体通过转向架区域时产生了不同尺度和方向的复杂涡结构，上游几何体周围产生的涡向下游传播并与下游几何体相互作用，从而在转向架后端形成高湍流度尾迹区；转向架结构近壁流场内形成的四极子噪声中，体偶极子声源高于体四极子声源，成为四极子主要声源；转向架、转向架舱后壁面以及尾部等部位的涡脱落、流动分离和流体相互作用剧烈，涡结构发展集中，几何体表面压力脉动变化显著，诱发形成偶极子气动噪声源；所得气动噪声降噪措施中，在高速列车排障器底部后端设置凹坑或在转向架舱前缘设置锯齿形扰流板，可抑制该部位分离剪切层的形成与发展，削弱转向架舱前缘流动分离并缓和尾迹与舱内各部件的流动冲击作用，干扰转向架周围大尺度湍涡的形成和脱落，减少由几何体表面压力脉动诱发气动噪声的产生；排障器前后贯通，气流流经后干扰了前车轮附近的湍涡形成和发展，减弱转向架舱前缘分离边界层与转向架结构的相互作用，降低了转向架舱内特别是车轮周围的流动分离和涡脱落，使得流致噪声得到有效控制；另外，转向架舱外侧安装流线型裙板，可以减弱转向架区域流动冲击与湍流脉动，削弱转向架舱外剪切层冲击和流动分离，抑制转向架舱内结构表面压力脉动，降低气动噪声的产生与辐射；声学风洞测试验证了转向架区域各气动噪声降噪措施的有效性。