Drag Reduction Performance Analysis Of The Boat-type Tractor Hull Based On Multi-phase Flow

Boat-type tractor is a special kind of paddy field agricultural machinery equipment in our country.The hull is floating and sliding on the surface of the soil.Obviously,the interaction between boat and paddy soil is the main source of working resistance.Therefore,reducing hull resistance will improve the efficiency of boat-type tractor and reduce energy consumption.Based on ship theory,Computational Fluid Dynamics and the existing boat-tractor hull,the viscous flow model of boat-tractor hull in varieties of non-Newtonian fluids is established by the method of numerical simulation.In order to find a ship with smaller resistance,viscous resistance and wave resistance of various kinds of hulls under different operating speeds are obtained.The work completed is as follows:(1)The experiment of soil rheology of the paddy field.Three typical working conditions of paddy soil are collected,and the rotational rheometer is used to obtain the plastic viscosity and yield strength,and the density is measured by balance,which lay the foundation for the further study.(2)Numerical simulation of viscous resistance of ship hull based on single-phase flow.The Single-phase flow numerical model of ship type tractor hull is established to study the relationship between the angles of the hull plate,the working speed and the viscous resistance,and the drag reduction rate is obtained and the drag reduction mechanism is analyzed.The results show that the drag reduction rate increases with the inclination of the hull at the same velocity,and the hull with angle of 30 degrees in comparison with the plate hull,the maximum drag reduction rate is 16.8% under the common working speed.(3)Numerical simulation of ship viscous resistance and wave resistance based on two-phase flow.A numerical model of the single-phase flow and two-phase flow of the boat type-tractor hull is established.The relationship between the working speeds of the two hulls and the viscous resistance and wave resistance resistance is studied.The drag reduction rate is obtained and the influence of the hull on the wave resistance is discussed.The results show that the maximum viscous resistance reduction rate of the hull is 13% in the paddy soil,and it does not have the effect of reducing the resistance.(4)Numerical simulation of three phase flow hull resistance with water layer and experimental verification.The single-phase flow model,two-phase flow model and the three-phase flow numerical model with water layer are established in order to obtain the viscous resistance and wave resistance resistance and analysis of wave height curve,and the ship model experiment is carried out to compare the ship wave.The results show that the soil parameters in the paddy field are the important factors for the resistance of the hull.Dissatisfaction with the condition of dynamic pressure lubrication,the resistance reduction effect of water layer is not ideal and and a feasible solution is put forward.Compared with the ship wave shape,the ship model experiment is in good agreement with the numerical calculation result,that is,the numerical calculation is reliable.In conclusion,based on the existing boat-type tractor hull,and the non-Newtonian fluid rheological model of paddy soil,this paper establishes three types of numerical analysis model of the multi-phase flow of soil in typical working conditions,analyzes the viscous resistance and wave making performance of the hull,and carries out the ship model experiment to verify the wave shape.The research is of guiding significance for numerical simulation of hull resistance,ship drag reduction design and improving the working efficiency.