Numerical Study On Vortex-induced Vibration Of Locomotive Carbody In Tunnel Based On Fluid-structure Interaction

Since the operation of the CR200J EMU Train,the motor car at the tail of EMUs and the cab of the control car have been showing poor lateral stability,especially in single-track tunnels,where the lateral low-frequency swaying range of the car body is more obvious.Such instability is difficult for drivers and passengers to stand,which has attracted great attention from China State Railway Group Co.,Ltd.,locomotive factories,and scientific research institutes.In June 2020,the Locomotive&Car Research Institute of China Academy of Railway Sciences tested the 160 km·h^-1 EMUs’small radius curve-passing performance and studied whether it could successfully get through the tunnels within the governance of China Railway Xi’an Group Co.,Ltd.It was found that when the train passes through the single-track tunnel,two motor cars and two control cars have the same problem of obvious periodic vibration at the tail of the vehicle.The main frequency range of the vibration is 1～2 Hz,the lateral stability index of the cab of the motor car reaches 3.4,and the acceleration reaches 2.4 m·s^-2.Considering that the motor car and the control car have a similar head shape,it is preliminarily concluded that the vibration is related to the disturbance of airflow at the tail of the train in the tunnel.To solve this problem,theoretical and numerical simulations of fluid-structure interaction of high-speed locomotive in a tunnel are carried out in this thesis.Firstly,considering that the wake flow field of the train has complex turbulence,the flow around a bluff body with a simple shape is taken as a typical vortex-induced vibration model for numerical simulation based on the UDF development of FLUENT,structural dynamics principle,and chimera grid method.Then the numerical simulation in a typical model of flow around a circular cylinder is also performed,after which the above two results are compared.Results show that the velocity grade and edge shape have a great influence on vortex removal at the tail of the bluff body.Furthermore,a two-dimensional fluid-structure interaction model of two-degree-of-freedom car body structure in the tunnel is established.Based on that model,the vortex removals in the wake flow field of the train under different working conditions including running speed,the length-width ratio of head shape and single-and double-track tunnel are investigated.Results show that both running speed and the length-width ratio of head Shape will affect the vortex-off frequency and vibration amplitude of the train tail.With the increasing running speed and the length-width of head form,the vortex-off frequency will also increase.Compared with the performance in double-track tunnel,the aerodynamic effect at the tail of the train in the single-track tunnel is more obvious.Finally,to study the effects of fluid-structure interaction vibration on the vehicle lateral dynamic performance and propose effective measures,a fluid-structure interaction calculating model based on real-time collaborative simulation of FLUENT fluid calculation and MATLAB/Simulink locomotive dynamics analysis is established.Simulation results are as follows:under the extreme wheel-rail contact geometry with low equivalent conicity,poor primary hunting stability of locomotive leads to the poor lateral stability of the car body;Fluid-structure interaction can improve the amplitude of lateral vibration of the car body,but it has little effect on vibration frequency.By reducing the damping of the anti-hunting damper and increasing the damping of the secondary lateral damper,the lateral vibration acceleration of the rear end of the car body can be reduced by 25%and 29%,respectively.