Research On Drag Reduction Of Transplanter Float With Bionic Microstructures

The float is one of the important mud engaging parts of rice transplanter.And the sliding resistance will be generated between transplanter float and muddy water during transplanting work,which has resulted in the serious waste of energy and reduced the working performance.Therefore,it has an important significance to reduce the fluid resistance of the transplanter float.This research was supported by the study on drag reduction mechanism of transplanter float bottom with bionic scalelike micro structure of the national natural science foundation of china(51305282).The microstructures of fish Ctenopharyngodon idellus scales were selected as biology prototype to design bionic surface of which the drag-reduction characteristics were investigated.Further,the bionic microstructures were applied to the rice transplanter float in order to analyze the flowing friction characteristic of mud near the float surface and the drag reduction effect.The main contents and conclusions of this paper are as follows:The morphology,structure characteristic parameters and overall distribution of the microstructures of fish scales were analyzed in detail,and the main size parameters of the microstructures on every regions were extracted exactly.Next,the regular pattern distribution microstructures on the area of the apical of fish scale were selected as the biology prototype for bionic design,and the 3D simplified model of bionic surface with scalelike microstructure was established clearly.Numerical simulation on bionic surface with scalelike microstructures were investigated using the computational fluid dynamics software FLUENT,and the hydrodynamic characteristics of water-trapping and vortex near bionic surface were analyzed.Meanwhile,the drag reduction mechanism of the bionic surface was proposed,that is to say,a low-speed vortex was formed behind the "crescent" unit and it effectively prevented the low-speed fluid from moving out the boundary layer,which generated a low-speed and stable water-trapping area that played a fluid lubrication role.Thus,the bionic surface showed remarkable drag reduction effect.The results of resistance test showed that the "crescent" microstructures had a great drag reduction effect at a low speed.What's more,the drag reduction rate displayed a downward trend with the increase in flow speed.Consequently,when the rate was 0.66 m·s-1,the drag reduction effect was the best,the maximum drag reduction rate was 2.805%.Numerical simulation and resistance tests on bionic float samples were conducted in order to explore the optimal combination of drag reduction design,that is,the height,width,the space between neighbouring ridges,and the incoming flow velocity was 0.05 mm,0.45 mm,0.20 mm,and 0.70 m·s-1,respectively.Meanwhile,the results also showed that the height of crescent microstructure had significant effect on the drag reduction effect of bionic surface,but the others were not.Orthogonal experiment was carried out to analyze the primary and secondary sequence affecting the sliding resistance of transplanter float bottom,i.e.the float model>weight of float sample>the forward speed.As a result,the optimal combination of the factors,the forward speed of 0.4 m·s-1,weight of 0.7 kg and bionic float,was determined,which was the best drag reduction effect.And the maximum drag reduction rate was 22.90%.In addition,numerical simulation on the bionic float samples was analyzed in mud environment using the computational fluid dynamics software FLUENT.Consequently,the pressure distribution and velocity distribution of the mud near bionic float were obtained,and the best drag reduction rate of the bionic float sample with "crescent-like" microstructures was 28.50%.In this paper,the study on drag reduction of the transplanter float with bionic microstructures will improve the tribological characteristic of float bottom,which can achieve drag reduction.This work develops the structural bionics in paddy field machinery and provides significant references for bionic drag reduction research in engineering machinery,agricultural machinery,transportation and so forth.