Research On The Drag Reduction Characteristics Of Hull Structure For The Boat-type Tractor

The boat-type tractor is a special agricultural machinery in China.Its "floating and slide" working principle enables the hull to float on the surface of the mud layer without damaging the hard bottom of the soil.It is suitable for paddy fields in south China.The ship tractor running paddy field produces the sliding resistance which interacts with the mud,there will be an interactive sliding resistance between the ship tractor and mud.Reducing the sliding resistance can improve the working efficiency of the boat-type tractor.Therefore,the optimal design of drag reduction for hull structure of boat-type tractor is studied in this dissertation.The domestic scholars mainly explore the resistance characteristics of smooth hull in the research of boat-type tractor drag reduction,but the research on the drag reduction performance of non-smooth surface hull is relatively lack.In this dissertation,the non-smooth surface drag reduction structure is designed on the hull of a boat-type tractor,and the drag reduction performance of the non-smooth surface hull under different structures is studied.Firstly,the existing boat-type tractor was selected as the research object,3D model and numerical simulation model were established.According to the boundary layer theory different non-smooth surface structure hull is selected.After the rheological parameters were selected,a watershed model was established for each hull,then the overall grid and boundary definitions were divided for computational fluid dynamics simulation.According to the bionics principle,when selecting the non-smooth surface structure,the design of different shape,size and configuration of non-smooth surface of the hull structure,calculate the optimal non-smooth surface drag reduction and optimal drag reduction performance of hull structure,the optimal structure of non-smooth surface drag reduction configuration in the optimal drag reduction at the bottom of the hull,the performance of the ship drag reduction effect of tractor work better.The mechanism of drag reduction is discussed from two aspects of velocity cloud diagram and pressure cloud diagram,the validity of numerical simulation results is verified by experiments.In the end,the new type of hull with bar and the double bottom was designed,and the pit structure was arranged on the bottom of the two new types of hull in a rectangular arrangement,so as to find an optimal anti-drag effect.It was found that the pit structure with a diameter of 18 mm and a depth of 11 mm had the best drag reduction effect among the non-smooth surface structures.The rectangular structure was arranged on the battle-type hull,and the drag reduction rate reached 12.5%.In this dissertation,the study on the hull of a new type of the boat-type tractor greatly reduces the resistance in running,which is of great significance to the improvement of the working efficiency of the boat-type tractor.