Development And Application On Multiphase Flow Computational Model Of High-speed Train With OpenFOAM

With the rapid development of China high-speed railway and the continuous increase of the train speed, the train safety operation under the extreme climate condition has become more and more complicated in different region and season. It is considerably concerned to study the aerodynamic characteristics and safe train operation of high-speed train under extreme weather conditions such as strong cross-wind and heavy snowstorm.Based on open source CFD platform OpenFOAM, the Eulerian method is adopted to conduct the numerical simulation. Based on the incompressible Navier-Storkes equation, standard k-ε turbulence model, and Eulerian two-phase model, the aerodynamic performance of a high-speed train under different weather conditions are simulated. Our numerical results of single-phase flow around the high speed train are compared with commercial software FLUENT, and good agreement prove the plausibility of our OpenFOAM model. For better simulation accurancy and efficiency of OpenFOAM, we have studied the influence of numerical parameter and set-up, for example, the boundary conditions, discrete scheme, grid accurancy, high-efficiency drag model (GidaspowSchillerNaumann), friction stress model (Schaeffer) reflecting the particles_phase nature, as well as effective turbulence model. Effects of these numerical parameters on the simulation results are investigated in details.The validated OpenFOAM model was then used to study the aerodynamic characteristics of high-speed train in strong cross-winds and strong snowstorm weather conditions. Results show that in the cross-wind weather, the lift and side forces of high speed train increase with the cross wind speed. With increasing side force and the lift force, it is possible to cause the train instability and even overturning. In snowstorms, the lift force, side force, and rolling moment of the train increase significantly under snow conditions than no snow condition. The reason is that the densed snow particles fall on the train and the interaction between the snow and the train wall introduce more aerodynamics force besides the forces by the air. Train side force increase plays a dominant role in snowstorm, which may further deteriote the train operation safety. In order to study the impact of aerodynamic changes in extreme weather on the train safety, a quasi-static stability analysis using the moment balance is utilized to determine the limit safety speed of train under different snow and wind levels. Results show that the train is more easily to overturn on the inner curve track. The train limiting speeds under snow decrease about20%-50%, comparing to that of without snow, which means that the train is more easily to overturn under snow condition.