真空管道磁浮交通气动特性的尺度效应

Scale Effect of Aerodynamic Characteristics in Evacuated Tube Maglev Transport

为了探究管道列车的尺度对波系、尾涡以及气动载荷的影响,基于CFD软件建立三种模型尺度(1∶1,1∶5和1∶10),同时考虑两种悬浮间隙关系(车轨相对间隙不变和绝对悬浮高度不变)的模型;采用改进的延迟分离涡模拟(IDDES)湍流模型和重叠网格技术模拟了列车在管道动态运动,并用风洞试验数据验证了数值方法和网格策略的合理性.研究结果表明:列车尺度(雷诺数)增大,车前活塞区域变长,尾流扰动区范围缩短;雷诺数对近尾流区的涡对演化影响较小,但在远尾流区,随着列车尺度减小,涡对脉动变强,涡对强度的差异导致了车后正激波形态的差异;列车表面最大正压值和最大负压值均随着列车尺度增大而增大,悬浮间隙对最大正压值影响较小,但与最大负压值成正相关关系;尺度效应从压差阻力和摩擦阻力两方面共同影响气动阻力,整车摩擦阻力和头、中间车的压差阻力与雷诺数正相关,但是尾车压差阻力受附着激波的强度影响恰恰相反;列车尺度和悬浮高度均对升力影响较大.相对于全尺寸模型,1∶10模型(悬浮高度20 mm)的最大正压值减小3.82%,最大负压值增大3.94%,整车总阻力增大8.64%,头车升力减小101.56%,尾车升力增大15.88%.

In order to investigate the effect of the scale of a tube train on wave systems,wake vortices,and aerodynamic loads,three model scales(1∶1,1∶5,and 1∶10)were established based on computational fluid dynamics(CFD)software,and two types of suspension gap relationships(constant relative gap between tracks and constant absolute suspension height)were considered.The improved delayed detached eddy simulation(IDDES)turbulence model and the overlapping mesh method were utilized to simulate the train’s dynamic motion in the tube,and wind tunnel test data were used to validate the numerical method and mesh strategy.The study results demonstrate that as the train scale(Reynolds number)increases,the front piston region lengthens,and the wake disturbance region shrinks in extent;Reynolds number has less effect on vortex pair evolution in the near wake region,but in the far wake region,vortex pair pulsation becomes stronger as the train scale decreases,and the difference in vortex pair strength leads to differences in the normal shock wave pattern in the rear of the train;the maximum positive and negative pressure values on the train surface increase as the scale of the train increases;the suspension gap has less influence on the maximum positive pressure value,but it is positively correlated with the maximum negative pressure value.The scale effect affects the aerodynamic drag from both pressure drag and friction drag.The friction drag of the whole train and the pressure drag of the head and middle trains are positively related to the Reynolds number;the pressure drag of the tail train,however,is influenced by the strength of the attached shock wave in an opposite way.Both train scale and suspension height significantly affect the lift.Compared with the full-scale model,the 1∶10 model(suspension height of 20 mm)has a 3.82%reduction in maximum positive pressure,a 3.94%increase in maximum negative pressure,an 8.64%increase in total drag,a 101.56%reduction in the lift of the head train,and a 15.88%increase in the lift of the tail train.