高速列车头型长细比对气动噪声的影响

高速列车的头尾车外形对气动噪声具有重要的影响.工程实践中随着车速的增加,车辆头部越来越细长,日本高速磁悬浮列车实践中甚至出现了具有极端长细比的头部形状.本文以讨论头型长细比对列车气动噪声的影响规律为出发点,应用非线性声学求解器(NLAS)和FW-H声学比拟法的混合算法,在3种运行速度下对基于CRH380A高速列车头型概化的4种不同头型长细比的模型车的气动噪声进行了数值模拟.给出了不同头型长细比列车的流场特征、气动阻力和气动噪声.结果表明,列车的气动总阻力随头型长细比的增大而减小,且头型长细比对列车总气动阻力的影响随运行速度的增加而增强.而头型长细比对气动噪声的影响呈现出较为复杂的影响,并不存在单调的影响关系;综合考虑气动阻力和气动噪声,长细比最大的头型综合性能较优,但差异并不显著,因此在不考虑微气压波等因素的条件下,简单增加车头长细比并不一定能带来明显的气动噪声性能提升.

STUDY ON THE INFLUENCE OF THE NOSE SLENDERNESS RATIO OF HIGH-SPEED TRAIN ON THE AERODYNAMIC NOISE

In the high-speed train design, the nose shape is a crucial control factor influencing not only aerodynamic performance but also the aerodynamic noise. In the engineering practice, the nose shape becomes more and more slender along with the increasing of the design speed, e.g. the Japanese high-speed maglev train L0 series even has a 15 m long slender nose (the slenderness ratio reach to 8.8). This study aims to discuss the influence of the slenderness ratio of the nose shape on the aerodynamic noise. The hybrid numerical method of nonlinear acoustics solver (NLAS) and Ffowcs Williams-Hawkings (FW-H) acoustic analogy method is employed to study the aerodynamics noise characteristics. The numerical method is validated with a standard wind mirror test case and a set of acoustics wind tunnel experiments of the CRH380A train. The shape of the CRH380A train is chosen as a bench mark, and four different nose shapes of different slenderness ratio under different running speed situation are studied with numerical simulation. The flow field, aerodynamic drag, and the aerodynamic noise are obtained and discussed. The result shows that the total drag decrease with the increase of the slenderness ratio, and this effect enhances when the train speed increases. However, the influence of the slenderness ratio on the aerodynamic noise is much complex as no simple trend is observed. Considering both the aerodynamic and aeroacoustics characteristics, the train with the most slender nose shape is the best while this advantage is not notable compared with the second-best. Thus, simply increase the slenderness does not necessarily result in better aerodynamic noise performance if the effect of tunnel boom is not considered.