Explore the vast range of titles available.

Soil adhesion is one of the important factors affecting the working stability and quality of agricultural machinery. The application of bionic non-smooth surfaces provides a novel idea for soil anti-adhesion. The parameters of sandy loam with 21% moisture content were calibrated by the Engineering Discrete Element Method (EDEM). The final simulated soil repose angle was highly consistent with the measured soil repose angle, and the obtained regression equation of the soil repose angle provides a numerical reference for the parameter calibration of different soils. By simulating the sinusoidal swing of a sandfish, it was found that the contact interface shows the phenomenon of stress concentration and periodic change, which reflects the effectiveness of flexible desorption and soil anti-adhesion. The moving resistance of the wedge with different wedge angles and different serrated structures was simulated. Finally, it was found that a 40° wedge with a high-tail sparse staggered serrated structure on the surface has the best drag reduction effect, and the drag reduction is about 10.73%.

Idling power loss suppression techniques of hydraulic retarders in non-braking operating conditions are of great significance to improve vehicle driving efficiency. Most proposed idling power loss suppression devices require auxiliary operating parts, take up a lot of space and increase the load on the vehicle. In this study, the plunger spoiler was optimized with a non-smooth bionic surface for improved performance and compactness. Hydraulic retarders with traditional smooth spoilers and different bionic non-smooth surface spoilers were simulated and tested to investigate the effects of bionic non-smooth surfaces on idling performance. The numerical results indicated that the bionic spoilers could disturb the fluid flow, lower the blade pressure and increase the internal energy dissipation, leading to reduced rotor drag and lower idling power loss. The mechanism of drag reduction on rotor and efficiency improvement was discussed. The experimental data showed that bionic non-smooth surface spoilers reduced idling torque by 11.7% at a rotor speed of 3000 r/min, compared to the traditional smooth surface spoilers. In conclusion, the hydraulic retarder with an optimized bionic surface spoiler is able to reduce idling power loss and improve transmission efficiency effectively.

The borehole hydraulic mining method has unique advantages for underground oil shale exploitation. Breaking rock with a high-pressure water jet is a crucial step to ensure the smooth implementation of borehole hydraulic mining in oil shale. The hydraulic performance of the nozzle determines the efficiency and quality of high-pressure water jet technology. To obtain a superior hydraulic performance nozzle, based on the bionic non-smooth theory, a circular groove was selected as the bionic unit to design a bionic straight cone nozzle. The structural parameters of the circular groove include the groove depth, width, and slot pitch. The optimization objective was to minimize the pressure drop, where the fluid has the least resistance. A genetic algorithm was used to optimize the structural parameters of the circular grooves in the inlet and outlet sections of the bionic straight cone nozzle. The optimal structural parameters of the nozzle were as follows: the inlet diameter was 15 mm, the inlet length was 20 mm, the outlet diameter was 4 mm, the length-to-diameter ratio was 3, and the contraction angle was 30°. In addition, in the inlet section, the groove width, slot pitch, and groove depth were 3.9 mm, 5.2 mm, and 5.5 mm, respectively, and the number of circular grooves was 2. Moreover, in the outlet section, the groove width, slot pitch, and groove depth were 2.25 mm, 3 mm, and 5.5 mm, respectively, and the number of circular grooves was 2. The CFD numerical simulation results showed that under the same numerical simulation conditions, compared with the conventional straight cone nozzle, the bionic straight cone nozzle velocity increase rate could reach 13.45%. The research results can provide scientific and valuable references for borehole hydraulic mining of high-pressure water jets in oil shale drilling.

Based on the bionic non-smooth surface theory, this article carries out (1) design of the structure of bionic non-smooth sealing rings and toothed bars of the sealing structure and (2) finite element simulation study on the bionic non-smooth surface structure of roller-cone bits. The result shows that (1) when the parameter Y is equal to the rack angles, the maximum pressure of the Type B is smaller than that of the Type A, while the equivalent stress of the Type A is smaller than that of the Type B; when the parameter Y is equal to the tooth distribution, the maximum pressure and the equivalent stress of the rack angle of 30° are smaller than that of the rack angle of 20°; and when the rack angle is equal to the tooth distribution, the maximum contact pressure and the equivalent stress of the tooth decrease with the increase in the parameter Y. (2) Compared with the O-shaped sealing rings, the new tooth bars avoid the problem of over-large contact area. (3) The grid-shaped sealing structure can increase the wear resistance of rubber rings and delay their wear and aging, thus improving their service life.

Bionic non-smooth surface is widely applied in metal and ceramics materials. In order to introduce this technology to high pressure seawater pump, the influence of bionic non-smooth surface on the engineering plastics used in pump should be investigated. The comparative tests are carried out with a ring-on-disc configuration under 800, 1000, 1200 and 1400 r/min in order to research the influence of the bionic non-smooth surface on glass fiber-epoxy resin composite（GF/EPR） under natural seawater lubrication. The disc surfaces are textured with five kinds of pits, which are semi-spherical, conical, cone-cylinder combined, cylindrical pits and through holes, respectively. A smooth surface is tested as reference. The results show that the lubrication performance of dimpled GF/EPR sample is much better than that of the smooth sample under all rotational speeds. The semi-spherical pits surface has more obvious friction reduction than the others, which shows that the least reduction is approximately 43.29% of smooth surface under 1200 r/rain. However, the wear level is only marginally influenced by dimples. The surface morphology investigations disclose severe modifications caused by abrasive wear primarily. The results are helpful to vary friction properties of GF/EPR by non-smooth surface, or provide references to the design of non-smooth surfaces under certain condition.

Due to the complexity of the working conditions and the diversity of application scenarios, the normal operation of a fan, whether volute tongue, volute shell surface, or blade, often encounters some unavoidable problems, such as flow separation, wear, vibration, etc.; the aerodynamic noise caused by these problems has a significant impact on the normal operation of the fan. However, despite the use of aerodynamic acoustics to design low-noise fans or the use of sound absorption, sound insulation, and sound dissipation as the main traditional noise control techniques, they are in a state of technical bottleneck. Thus, the search for more efficient methods of noise reduction is looking toward the field of bionics. For this purpose, this paper first analyzes the mechanism of fan noise in the volute tongue and blades, and then, this paper reviews the noise control mechanism and improvement research using the bionic structures in the volute tongue structure, the contact surface of the volute shell, and the leading and trailing edges of the blade in the centrifugal fan. Finally, the current challenges and prospects of bionic structures for aerodynamic noise control of centrifugal fans are discussed.

Current research on wind energy piezoelectric energy harvesters (PEHs) mainly focuses on tandem smooth cylinder energy harvesters; however, the traditional tandem smooth cylinder energy harvester has low voltage output and narrow energy harvest bandwidth. In this study, a D-type bionic fin is designed and installed on a smooth cylindrical surface to improve its performance. The influence of the spacing ratio on the amplitude and voltage of PEHs with D-type bionic fins added under elastic interference was investigated through wind tunnel tests. Three installation positions were designed: only installed upstream, only installed downstream, and not installed upstream and downstream (BARE). It was found that the maximum displacement of the upstream PEH (UPEH) was not apparently affected by the D-type bionic fin. Contrastingly, the fin changed the maximum amplitude from a small to a large spacing ratio for the downstream PEH (DPEH). D-type bionic fin can enhance energy harvest performance by coupling “coupled vortex-induced vibration” and wake induced galloping, increasing the surface velocity of PEHs and expanding the bandwidth of the voltage harvested by the PEHs. Analysis of the power under the experimental wind speed showed that installing D-type fins in the PEHs can increase the output power of the upstream and downstream PEHs by 392.28% and 13%, respectively, compared with that of the BARE-PEH. Additionally, computational fluid dynamics was used to analyze the flow pattern, wake structure, and lift coefficient of the PEHs, and to explain why the upstream D-type bionic fin installation has an impact on the harvest performance of the upstream and downstream PEHs at a spacing ratio of 1.5. This study provides an efficient and simple scheme for designing wind PEHs.

As a global concern, environmental protection and energy conservation have attracted significant attention. Due to the large carbon emission of electricity, promoting green and low-carbon transformation of the power industry via the synergistic development of clean energy sources is essential. Rotating machinery plays a crucial role in pumped storage, hydropower generation, and nuclear power generation. Inspired by bionics, non-smooth features of creatures in nature have been introduced into the structure design of efficient rotating machines. First, the concept and classification of bionics are described. Then, the representative applications of non-smooth surface bionic structures in rotating machineries are systematically and comprehensively reviewed, such as groove structure, pit structure, and other non-smooth surfaces. Finally, conclusions are drawn and future directions are presented. The effective design of a bionic structure contributes toward noise reduction, drag reduction and efficiency improvement of rotating machineries. Green and ecological rotating machinery will remarkably reduce energy consumption and contribute to the realization of the “double carbon” goal.

The characteristics of the material transported by the two-vane pump can cause the impeller to wear out, leading to a deterioration in hydraulic efficiency. Appropriately, the research goal of this paper is to consolidate the anti-wear performance of the two-vane pump conveying a solid-liquid two-phase flow. Based on the bionic principle and the anti-wear structure of blood clams, the circular non-smooth structure adapted from blood clams is arranged in the wear-prone area. Through numerical simulation, we compare the main indexes of the pump: the head, the pressure distribution, the vortex pressures, and the average wear rate, to reveal the wear resistance mechanism of circular non-smooth structures. The results illustrate that the use of a circular non-smooth structure does not modify the external characteristics of the pump; the pressure distribution inside the impeller is similarly consistent, and the vortex pressures are all approximately the same. The average wear rate is higher when the diameter of the circular non-smooth structure is either 0.25 mm or 0.30 mm, and the simulation results are poor. At a diameter of 0.20 mm, the average wear rate of circular non-smooth blades is at its lowest point. The circular non-smooth surface structure causes impurities to be “caught” by the vortex zone and not freely struck against the wall, resulting in the particles migrating away from the blade.

With the development of economy, the energy problem is becoming more and more seriously, which is closely related to resistance, and drag reduction means to save energy. Research on the technology of drag reduction plays an important role in the area of energy saving and its utilization rate enhancing. Using the method of bionic surface drag reduction to reduce the surface friction drag in a fluid medium has become a hot topic in the research area of drag reduction. Furthermore, through analyzing approaches of bionic surface drag reduction on the necessary of energy saving, energy utilization rate enhancing and drag reduction theory system improving, the research progress of the dynamic bionic non-smooth surfaces and bionic jet surface drag reduction technology are summarized in detail, the main trend of non-smooth drag reduction technology research and jet drag reduction technology is reviewed.