Research On Air Layer Drag Reduction Performance Of Boat-type Tractor

The boat-type tractor in the operation of the paddy field there are problems such as large driving resistance,low efficiency,etc.This paper selects the combination of boat-type tractor and air layer drag reduction technology,using fluid dynamics simulation software to construct a two-phase flow model to study its drag reduction performance in the paddy field mud,and verify its conclusions through boat model tests.Specific work was completed as follows:(1)By comparing the physical phenomena and resistance changes of the flat-bottom boat and the groove boat with air injection,and analyzing the resistance reduction mechanism of the groove boat with air injection,the research results show that:the injection of air into the bottom groove can form a continuous air layer,so that the bottom groove is separated from the external environment to change its contact form and achieve the purpose of reducing resistance,and in the paddy field mud with different water content can obtain a certain resistance reduction effect.(2)In order to study the factors affecting the air layer drag reduction of boat-type tractor,the three important parameters of inlet velocity,air flow and hull inclination were analyzed in depth,the research results show that:when changing the inlet velocity only,the coverage area of air layer will decrease with the increase of inlet velocity,and the drag reduction rate is decreasing;the increase of air flow increases the coverage area of air layer,corresponding to the total drag reduction,after the air flow exceeds a certain limit,the total resistance increases in the opposite direction;the inclination angle of the hull is not conducive to the air layer drag reduction,when the trim angle is 1 degree,the air layer ruptures and the total resistance increases by 12N,when the trim angle is 2 degrees,the air layer at the bottom of the ship ruptures and at the same time the air leaks on both sides of the ship,the total resistance increases by 36N.(3)For the groove structure,the initial groove A with different groove depth and the improved groove B,C and D are designed to study the drag reduction effect and air layer stability,the results show that:when running smoothly,the 0.03m groove depth groove A has the best drag reduction effect,the absolute drag reduction rate is 27.2%;The rib length 0.7m groove B has the best air layer stability when the transverse inclination angle is 3 degrees.The air layer coverage rate is 92%,and the absolute drag reduction rate is 14.7%.(4)In the 2:1 reduced size ship model test,by changing the three influencing factors of inlet velocity,air flow rate and hull inclination,it is found that the ship model test phenomenon is basically consistent with the simulation test;in the ship model test verification of slot B with rib length of 0.7m.the results show that the structure can effectively maintain the coverage area of the air layer when coping with the hull inclination,and the value of air layer coverage is 73%,which improves the stability of the air layer.