Effect of simplifying metro train bottom geometric structure on flow and motor heat dissipation
In numerical simulation,the simplification of geometrical structures can effectively improve the computational efficiency and reduce the computational cost.In this study,a three-dimensional,constant,compressible Reynolds-averaged Navier-stokes(RANS)equation-based model with thermal radiation was used to investigate the effects of three simplified models(A,B and C)of the bottom structure on the bottom flow field of a subway train as well as on the surface temperature distribution of the linear motors,and evaluate the computational accuracy and efficiency of the simplified models.The results show that the simplification of the bottom structure reduces the wake area behind the motor,which enhances the bottom flow.The more simplified the model,the higher the flow rate of the cooling air,and the circulation of the traveling air can be affected by the simplified geometric structure.The increase of cooling air flow affects the convective heat transfer of the motors,and compared with the original model,the three simplified models make the average value of the temperature of each motor decrease by 1.2%,2.4%and 7.5%,respectively.In order to improve the calculation efficiency on the premise of guaranteeing the calculation accuracy,considering the flow field distribution law and the temperature field calculation results of the underbody,only the structure of wheel axle,brake disk,transverse tie rod and suspension device of the bogie of the original model should be simplified.
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