基于CFD的双道超车过程气动特性分析

基于计算流体力学（CFD）中的动网格技术对双道超车进行了数值模拟，研究表明，双道超车过程中，3辆车周围均出现强烈的压强和空气流速变化，当主超车在两车之间时，流场变化更为复杂。随着车辆相对位置的变化，3辆车周围的涡形态发生明显变化，涡的变化消耗流场中的能量，使车身受力发生变化。行驶过程中，3辆车的侧向力、风压中心位置和横摆力矩均发生明显变化。绝对速度增加，主超车与被超车的最大侧向力均呈线性增长，给车辆行驶稳定性带来负面影响。     

Numerical analysis of vortex-induced vibration on a flexible cantilever riser for deep-sea mining system

The flexible cantilever riser, as a special form of the marine riser, can be encountered in a deep-sea mining system, where the bottom of the long vertical lifting pipeline is connected with the intermediate warehouse. The main objective of this paper is to investigate the effects of the bottom weight caused by the intermediate warehouse and the flow speed on the dynamic responses of the cantilever pipeline. A quasi-3D coupling algorithm based on the discrete vortex method and finite element method is employed to calculate the unsteady hydrodynamic forces and vortex-induced vibrations of this pipeline in the time domain, respectively. We first simulate the VIV of a long flexible riser with two fixed ends in a stepped flow to validate the feasibility of the present method. Then, systematic simulations of cross-flow VIV of the cantilever riser are carried out under a wide range of bottom weights and different current speeds. The number of the vibration mode shows the decreasing tendency with the increase of the bottom weight. In a certain range of the weight, the number of the dominant mode remains unchanged, while the vibration amplitude declines with increasing weight. An amplitude jump phenomenon can be observed when the transition of the dominant mode in two contiguous mode clusters occurs. Moreover, the higher-order modes are excited with the increase of the current speed.