Abstract
In this study, a bionic nonsmooth drag-reducing surface design method was proposed; a mathematical model was developed to obtain the relationship between the altitude of the nonsmooth drag-reducing surface bulges and the spacing of two bulges, as well as the speed of movement, based on which two subsoiler shovel tips were designed and verified on field experiments. The mechanism of nonsmooth surface drag reduction in soil was analyzed, inspired by the efficient digging patterns of antlions. The nonsmooth surface morphology of the antlion was acquired by scanning electron microscopy, and a movement model of the nonsmooth surface in soil was developed, deriving that the altitude of the nonsmooth drag-reducing surface bulge is proportional to the square of the distance between two bulges and inversely proportional to the square of the movement speed. A flat subsoiler shovel tip and a curved tip were designed by applying this model, and the smooth subsoiler shovel tips and the pangolin scale bionic tips were used as controls, respectively. The effect of the model-designed subsoilers on drag reduction was verified by subsoiling experiments in the field. The results showed that the resistance of the model-designed curved subsoiler was the lowest, the resistance of the pangolin scale bionic subsoiler was moderate, and the resistance of the smooth surface subsoiler was the highest; the resistance of the curved subsoiler was less than the flat subsoilers; the resistance reduction rate of the model-designed curved subsoiler was 24.6% to 33.7% at different depths. The nonsmooth drag reduction model established in this study can be applied not only to the design of subsoilers but also to the design of nonsmooth drag reduction surfaces of other soil contacting parts.
Highlights
Soil structural degradation is believed to be one of the most severe forms of soil degradation from traditional farming practices, which refers to the reduction in porosity between soil clumps, commonly known as soil compaction [1]
The subsoiler shovel tip E designed according to the mathematical model showed a good drag reduction effect, because the contact between the soil and the shovel tip surface was changed through surface reshaping
The mechanism of nonsmooth surface drag reduction was analyzed, the relationship between the altitude of the nonsmooth drag-reducing surface bulge, the distance between the bulges, and the movement speed was deduced, a nonsmooth drag-reducing surface design mathematical model was established, and the correctness of the model was verified through subsoiling experiments in the field
Summary
Soil structural degradation is believed to be one of the most severe forms of soil degradation from traditional farming practices, which refers to the reduction in porosity between soil clumps, commonly known as soil compaction [1]. Soil adhesion and subsoiling resistance are bigger; subsoiler shovel tip part is very easy to form a large piece of soil nucleus [18, 19], which leads to increased subsoiling energy consumption and poor subsoiling quality, and seriously subsoiling resistance increases sharply, directly affecting the routine operation or lead to the destruction of machinery [20] This problem can be solved by vibration, electroosmotic and bionic methods [21–23]. Natural organisms have evolved excellent functions and unique geometric structures over billions of years, and among them, animals that are good at digging have evolved superior digging organs These superior characteristics have been applied to the field of resistance reduction in agricultural machinery, and fruitful research results have been achieved [30, 31]. This is important for reducing the subsoiling resistance and improving the quality of subsoiling, as well as providing a model basis for the design of nonsmooth drag-reducing surfaces for the soil touching parts of agricultural machinery
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