The basic head shape of high-speed train is determined by its longitudinal type-line(LTL),so it is crucial to optimize its aerodynamic performance.Based on the parametric modeling of LTL constructed by non-uniform relational B-spline(NURBS)and the fluctuation pressure obtained by large eddy simulation(LES),the Kriging surrogate model(KSM)of LTL was constructed for low aerodynamic noise,and the accuracy of the KSM was improved gradually by adding the sample point with maximum expected improvement(EI)and the optimal point from optimization.The optimal objective was searched with genetic algorithm(GA).The results show that the total fluctuation pressure level(FPL)of the optimal LTL can be 8.7 dB less than that of original one,and the shape optimization method is feasible for low aerodynamic noise design.
To study the aerodynamic performance of a new six-axis X2K double-deck container vehicle,numerical simulation was done based on three-dimensional,steady Navier-Stokes equations and k-ε turbulence model.The results show that the pressure on the front surface of vehicle is positive,and others are negative.The maximum negative one appears as a "gate" shape on front surfaces.The pressure on vehicle increases with train speed,and pressure on vehicles with cross-loaded structure is smaller than that without it.The airflow around vehicles is symmetrical about train vertical axis,and the flow velocity decreases gradually along the axis to ground.Airflow around vehicles with cross-loaded structure is weaker than that without the structure.The aerodynamic drag increases linearly with the train speed,and it is minimum for the mid-vehicle.The linear coefficient for mid-vehicle without cross-loaded structure is 29.75,nearly one time larger than that with the structure valued as 15.425.So,from the view-point of aerodynamic drag,the cross-loaded structure is more reasonable for the six-axis X2K double-deck container vehicle.
