Influence of cross wind on the aerodynamic lift of tarpaulin

Railway wagon tarpaulin (referred to as tarpaulin) is an auxiliary appliance for railway wagons, which is used for wet, flammable goods or other goods that need to be covered with tarpaulins. For a long time, due to the shortage of railway boxcars, the transportation of grains and fertilizers has mostly been carried by open car thatch tarpaulins. The truck tarpaulins have played an important role in the increase of cargo transportation in railway transportation. When the tarpaulin of the truck runs in a windy area, the aerodynamic force of the tarpaulin, tarpaulin rope and tarpaulin rope net increases, and the phenomenon that the tarpaulin falls off or the rope hangs on the transport equipment often occurs; at the same time, in the electrified section, if the tarpaulin The cloth and rope net are overturned, which will directly endanger the stability of the catenary. At present, there are many researches on the aerodynamic performance of passenger trains in strong wind environment, but few researches on the aerodynamic performance of freight car tarpaulins. PVC three-proof tarpaulin coated high-strength polyester waterproof cloth is based on high-strength polyester canvas, coated with polyvinyl chloride (PVC) paste resin and added with accelerator (synthetic vegetable ester), antifungal agent, anti-aging agent A variety of chemical additives such as antistatic agent and antistatic agent are plasticized at high temperature. It has the properties of waterproof, plastic tarpaulin anti-mildew, cold resistance, aging resistance, anti-static and other properties; and the breaking strength, tear elongation and tearing strength are much better than traditional tarpaulins. It has a wide range of use and high intensity of use, and is a mainstream product in the modern tarpaulin market. In this paper, the author carried out a numerical simulation calculation of the aerodynamic lift of the tarpaulin under the action of the cross wind, and compared it with the actual vehicle test, and analyzed the influence of the train running speed and the cross wind speed on the aerodynamic lift when the train was running in a strong wind area. The aerodynamic lift of the tarpaulin varies with the speed of the train and the wind speed across the wind. The determination of the calculation area should take into account the full development of the airflow around and the flow field. Therefore, the width and height of the calculation area should be much larger than the cross-sectional size of the vehicle body. For the height size of the calculation area, the blockage of the air flow channel by the train model makes the channel narrower and the flow velocity increases, which is equivalent to changing the incoming flow speed. The height size of the calculation area should be increased as much as possible to reduce the model blocking ratio. influence on the calculation results. For the length of the inlet direction, in order to facilitate the given boundary conditions of the inlet, the inlet section should be as far away as possible from the car body to avoid the influence of the flow around the train, and to ensure that the inlet velocity distribution is uniform. For the length in the exit direction, vortices are generated on the leeward side of the train due to the viscosity of the air. In order to fully develop the air flow on the leeward side of the train, the boundary of the exit area should be kept away from the vehicle body model as much as possible, so that the boundary conditions of the exit can be given. The computational region is discretized using an unstructured grid. The mesh of the car body close to the wall is required to be finer, while the mesh of the part far from the car body adopts sparse mesh. Small computation and faster convergence. The surface element of the car body is a triangular mesh. Considering the influence of the cargo on the aerodynamic force of the tarpaulin after settlement, there is a gap between the tarpaulin and the cargo in the calculation model. The grid in this area is relatively dense, and the total number of grids in the calculation model is 1.6 million. about one. (1) When the train speed is corresponding, the aerodynamic lift on the tarpaulin increases with the increase of the crosswind wind speed, and the aerodynamic lift is approximately proportional to the square of the crosswind wind speed. (2) When the cross wind speed is corresponding, the aerodynamic lift on the tarpaulin increases with the increase of the running speed of the truck. (3) When the train speed is 64km/h and the cross wind speed is 31.5m/s, comparing the calculated and experimental values ​​of the aerodynamic lift on the entire D-type tarpaulin, the difference between the two is only 6.8%, which proves that the paper The numerical calculation method used is feasible.

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