| 1 | Effect of surface roughness on the aerodynamics of a high-speed train subjected to crosswinds显示文摘The irregularities on trains bodies are normally ignored or greatly simplified in studies concerned with aerodynamics.However,surface roughness is known to affect the flow characteristics in the boundary layer near the wall,hence potentially influencing the aerodynamic performance of a train.This work investigates the effects of roughness on the overall aerodynamic characteristics of a high-speed train subjected to crosswinds.Both experimental work and numerical work have been conducted to simulate a typical high-speed train with a 90?yaw angle,with both a smooth and rough surface.Roughness is applied to the roof of the train surface in the form of longitudinal strips.Results reveal that the addition of roughness is able to reduce the surface pressure on the roof and leeside of the train.Numerical results agree well with experimental ones and confirm that an increase in the roughness relative size can effectively restrain flow separation and reduce surface pressure.Moreover,numerical simulation results show that side force coefficient and roll moment coefficient subjected to rough model significantly decreased compared with smooth model.The conclusions drawn in this study offer the chance to derive critical reference values for the optimization of the aerodynamic characteristics of high-speed trains. | M.Y.Wang S.A.Hashmi Z.X.Sun D.L.Guo G.Vita G.W.Yang H.Hemida | 2021 | Acta Mechanica Sinica2021，37，7： | 1 |
| 2 | Aerodynamic shape optimization of an urban maglev train显示文摘With rapid development of urban rail transit,maglev trains,benefiting from its comfortable,energy-saving and environmentally friendly merits,have gradually entered people's horizons.In this paper,aiming at improving the aerodynamic performance of an urban maglev train,the aerodynamic optimization design has been performed.An improved two-point infill criterion has been adopted to construct the cross-validated Kriging model.Meanwhile,the multi-objective genetic algorithm and complex three-dimensional geometric parametrization method have been used,to optimize the streamlined head of the train.Several optimal shapes have been obtained.Results reveal that the optimization strategy used in this paper is sufficiently accurate and time-efficient for the optimization of the urban maglev train,and can be applied in practical engineering.Compared to the prototype of the train,optimal shape benefits from higher lift of the leading car and smaller drag of the whole train.Sensitivity analysis reveals that the length and height of the streamlined head have a great influence on the aerodynamic performance of the train,and strong nonlinear relationships exist between these design variables and aerodynamic performance.The conclusions drawn in this study offer the chance to derive critical reference values for the optimization of the aerodynamic characteristics of urban maglev trains. | Z.X.Sun M.Y.Wang L.Y.Wei F.B.Kong G.W.Yang | 2021 | Acta Mechanica Sinica2021，37，6： | 1 |
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