Multi-objective aerodynamic optimization design of high-speed maglev train nose

Purpose–The nose length is the key design parameter affecting the aerodynamic performance of high-speed maglev train,and the horizontal profile has a significant impact on the aerodynamic lift of the leading and trailing cars Hence,the study analyzes aerodynamic parameters with multi-objective optimization design.Design/methodology/approach–The nose of normal temperature and normal conduction high-speed maglev train is divided into streamlined part and equipment cabin according to its geometric characteristics.Then the modified vehicle modeling function(VMF)parameterization method and surface discretization method are adopted for the parametric design of the nose.For the 12 key design parameters extracted,combined with computational fluid dynamics(CFD),support vector machine(SVR)model and multi-objective particle swarm optimization(MPSO)algorithm,the multi-objective aerodynamic optimization design of highspeed maglev train nose and the sensitivity analysis of design parameters are carried out with aerodynamic drag coefficient of the whole vehicle and the aerodynamic lift coefficient of the trailing car as the optimization objectives and the aerodynamic lift coefficient of the leading car as the constraint.The engineering improvement and wind tunnel test verification of the optimized shape are done.Findings–Results show that the parametric design method can use less design parameters to describe the nose shape of high-speed maglev train.The prediction accuracy of the SVR model with the reduced amount of calculation and improved optimization efficiency meets the design requirements.Originality/value–Compared with the original shape,the aerodynamic drag coefficient of the whole vehicle is reduced by 19.2%,and the aerodynamic lift coefficients of the leading and trailing cars are reduced by 24.8 and 51.3%,respectively,after adopting the optimized shape modified according to engineering design requirements.

Research on numerical simulation of transient pressure for high-speed train passing through the most unfavourable length tunnel

The length of high-speed railway tunnel is an important factor affecting transient pressure of high-speed train.When the tunnel length is the most unfavourable,the transient pressure changes in the tunnel and on the surface of the train are the most severe,which may affect the safe operation of the train or damage the structure in the tunnel.Based on the three-dimensional,compressible,unsteady N-S equation and finite volume method,this paper uses the CFD numerical simulation method to study the change and amplitude distribution of the transient pressure on the train surface and the tunnel when a high-speed train passes through the most unfavourable length tunnel.A fast calculation method is proposed to save the cost of calculation;it has great applicability of pressure amplitude.The results show that the pressure distribution in the tunnel and on the surface of the train is affected by the train speed,the length of the train and the position of the measuring point.The minimum negative peak value in the tunnel appears at the position where the superposition phenomenon is the most severe,and the position will change with the speed of the train.There are two negative peak waveforms of the train surface pressure,and the first waveformn is greatly affected by the train speed.It improves a reference for studying the strength requirement of the most unfavourable length tunnels and trains,and ensures the safe operation of trains in tunnels of different lengths.