Aerodynamic Characteristics Numerical Simulation For The External Flow Field Of Multiple Units

With the emergence of high speed railway, the aerodynamic problem of high speed MU(Multiple Unites) stands out increasingly. The research on MU aerodynamics plays an important role on reducing aerodynamic resistance, enhancing aerodynamic performance, saving energy and saving transportation cost. Based on Navier-Stokes equation of uncompressible and compressible viscosity fluid and K-εturbulence model, creating the model of Multiple Units and using fluid simulation software as FLUENT, this paper makes simulations on external flow filed for 200km/h Multiple Units in open air and in crossing conditions.From the simulation on the external flow area of the MU in open air, pressure distribution of MU surface, aerodynamic drag coefficient, velocity distribution for flow area around the MU and the safety distance from the rear of the MU were concluded.As a special aerodynamic problem for high speed railway traffic, aerodynamic pressure pulse by crossing MU bring an important influence on safety of MU and comfort for passengers. This paper simulates the flow area of the crossing MU though sliding mesh technology and concludes distribution of aerodynamic drag coefficient, lift coefficient, side force and transit rule of crossing pressure pulse. Crossing pressure pulse curve is also plotted.Though the analysis on the simulation for external flow filed of the MU, we can make a comprehensive understand for the distribution of pressure and velocity for the external flow field of the MU in open air and in crossing condition, which offer a reliable foundation for the design of facility near railway and criterion about safety and the behavior for the worker near the rail. This paper has particle practical value for further develop the high speed railway in our nation.