| Land transport is mainly formed with rail transport and road transport, occupied a huge proportion in the transportation industry of world, and 16% of the total energy consumption paid for the aerodynamic drag of delivery system. Car and train was respectively the major carrier of road transport and railway transport. Currently, there is a large base of land transport and a steady growing demand, which has brought both great energy consumption and saving space. This paper research the air friction drag reduction problem of flat-plate surface under air film condition combined with theoretical analysis and simulated wind tunnel experiment, trying to reduce the air viscous friction resistance of flat-plate surface moving in air, by a drag reduction method seeping low speed air flow on the surface, and its drag reduction theory and an air film design scheme were studied.The air film condition means that low speed air seeping onto flat-plate surface artificially to mixing with that outer air with higher speed. Studies have shown that air seepage on flat-plate surface helped reducing the air viscous friction resistance.Based on which, this paper carried out the following research work surrounding with hybrid momentum theory of flat-plate boundary layer under air film condition:First, a wind tunnel machine was designed and made out for the air resistance simulated experiments, which can provide continuous, steady and speed adjustable laminar air flow, and wind resistance measurement record of experiment models.Then, friction theories of flat-plate surface under air film condition have been researched, the hybrid momentum theory was put forward, and the corresponding mathematical model was set up to describe relationships between air film and the outer air flow, the change of speed, thickness and viscous friction of the plate boundary layer, and the drag reduction mechanism.At last, the optimal technical conditions for air drag reduction of flat-plate surface under air film condition were investigated by the quadratic regression rotatable orthogonal design in the form of a regression equation’s minimum solution, the design with air vent diameter, seeping angel, seeping speed and speed of outer air flow as optimization factors. |
