Study On The Mechanism Of Viscous Drag Reduction By Wall Flow Control In High-speed Train

Air drag is a key factor contributed to train speed up, passenger comfort, reducing aerodynamic noise and energy consumption. The purpose of the research in this paper is to investigate the aerodynamic response of train with air flow vents, using Detached Eddy Simulation (DES), implemented by setting windshields as velocity-inlet in the commercial CFD (Computational Fluid Dynamics) package. The computational model of such a train is a1/20th scale of railway high-speed train.The DES results show a great effect of air flow vents on the train aerodynamic performance. Specifically, train with suction windshields had a bigger drag than that of the original car, and the drag increases7.3%with the increase of flow vent velocity changing to lOm/s. Meanwhile, a train with blow windshields has a smaller drag than that of the original train, and the drag decreases20%with the increase of flow vent velocity changing from0to lOm/s, and it almost stays unchangeable when velocity changes from10to20m/s. When the velocity of suction windshields and blow windshields are same, blow windshield has much more influence on train aerodynamic performance than suction windshields.Train with windshield Ⅰ setting as air flow vent set has different aerodynamic performance from train with windshield Ⅱ setting as air flow vent when the speed magnitude is same, and the former has bigger drag variation than the latter. When a train has hybrid suction-blow windshields, drag of train with blow windshield Ⅰ and suction windshield Ⅱ bigger than train with suction windshield Ⅰ and blow windshield Ⅱ. Drag reduction effect of train with two blow windshields is better than train with hybrid suction-blow windshields, which is in turn better than train with one blow windshield at any position.