Research On Drag Reduction Characteristics Of Non-smooth Surfaces Hull For The Boat-type Tractor

As the characteristic of agricultural equipment in China,the boat-type tractor has not destoried the soil hard bottom by using of the principle of floating,which would be suitable for complex paddy field of southern China.However,the boat-type tractor as the power of agricultural equipment,the sliding resistance of the hull in paddy field is the main resistance in working operation.If the sliding resistance could be reduced,the working efficiency could be improved and the fuel consumption would be reduced.At present,the drag reduction characteristics of non-smooth surface structure have been more studied in air or water and the research on drag reduction characteristics in non-newtonian fluid were less.In this article,the drag reduction performance would be explored through analysing the resistance properties of non-smooth surface hull of boat-type tractor in non-newtonian fluid.Based on the existing non-smooth surface drag reduction mechanism,the non-smooth surface hull of boat-type tractor is designed and its drag reduction performance in non-newtonian fluid is studied by using experimental test,simulation and analysis optimization.First of all,the flow field simulation model of non-smooth surface hull of boat-type tractor is established.Based on the rheological properties of non-newtonian fluid,the rheological parameters of slurry are measured by experiments.The structure size of non-smooth surface is estimated according to the formula of boundary layer thickness.According to the rheological parameters of slurry,the structure of non-smooth surface,the driving conditions of boat-type tractor and the principle of CFD simulation,the basin is established.Then it verifies the accuracy of the established simulation model that the resistance of smooth surface of the hull in water medium is calculated in comparison with the resistance formula of ship.Secondly,different shapes of non-smooth surfaces of the hull and smooth surfaces of the hull are simulated under different speeds by CFD software.By comparing the resistance value of smooth surfaces of hull and non-smooth surfaces of hull,the mechanism of drag reduction or increase of non-smooth surface resistance is analysed from the forming reason of frictional resistance and pressure resistance.It is found that the slurry in boundary lyaer separates from macro non-smooth surfaces.Then it changes the velocity gradient of slurry and results a drag reduction effect.Finally,based on the drag reduction mechanism of non-smooth surface hull,the influence rules of the hull's shape,size and other factors on drag reduction effect of non-smooth surface hull are explored by orthogonal factor analysis.And the size of non-smooth surface hull is optimized in order to make the resistance least.In short,the drag reduction rate of non-smooth surface of a new hull which is desgined in this paper can reach 12.5% by exploring the drag reduction performance of the non-smooth surface hull in slurry medium.The results show that the achievements of this paper can greatly reduce operating costs,reduce the pollution of environment andalso it establishes the foundation for optimizing the performance of energy-saving emission reduction and low resistance of other agricultural power equipments in paddy.