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To improve the friction and wear performance of the piston-cylinder liner friction pair, inspired by earthworms and leeches, 27 kinds of pistons with cylindrical pit arrays are designed and processed. Through a friction test, four superior textured pistons are optimized, and wear, life and thermal imaging tests are performed. Finite element analysis of the friction pair model is performed, and the friction and wear mechanisms are discussed. The results show that the pistons with cylindrical pit arrays have excellent friction and wear performance, less heat generation by friction, longer lives and less scratches on the cylinder liner. The temperature of the optimized textured pistons was reduced by around 5–10 °C. The wear amount of some textured pistons was reduced by over 50%, resulting in an improvement in their lifespan of at least 30% or more. The results of the finite element analysis indicate that the textured piston exhibited reduced deformation and favorable stress–strain distribution and satisfied the required contact pressure. [ABSTRACT FROM AUTHOR]

To improve the retained capacity and filtration efficiency, the liquid‒solid two-phase flow inside the cross-step filter was simulated using the computational fluid dynamics (CFD) and discrete element method (DEM) coupled method. The cross-step filtration utilises the shear layer in the slot to scour the particles deposited on the overflow mesh to the corner edge of the upstream rib, improving the filtration efficiency and retained capacity of the screen filter. Crossflow filtration was the predominant filtration mechanism at the overflow mesh, while dead-end filtration was predominant at the posterior mesh. The proportion of retained particles on the overflow mesh ranged from 10.1% to 18.2%. Along the mainstream, the average filtration velocity in the slot gradually increases and then decreases except in the last slot, accompanied by a constant number of particles trapped on the posterior mesh. Additionally, in the direction of the mainstream flow, the average shear velocity in the slot and the rotational velocity of the vortex initially increase and then decrease except in the first slot, resulting in a subsequent decrease and then increase in the amount of particles in the corresponding slot, with the exception that the greatest amount of particles is found in the end slot. The filtration velocity in the individual slots gradually decreases from the posterior mesh to the anterior mesh, with backflow occurring in the anterior mesh, while the shear velocity in the individual slots rises and then falls, with the greatest shear velocity along the overflow mesh. • CFD-DEM simulation of cross-step filtration with bridging mechanisms. • New optimisation simulation method for screen filters. • The relationship between vortex and particles in the filter slots • Comparison of cross-step filtration for filtration and collection [ABSTRACT FROM AUTHOR]

To improve the friction and wear performance of the piston-cylinder liner friction pair, inspired by earthworms and leeches, 27 kinds of pistons with cylindrical pit arrays are designed and processed. Through a friction test, four superior textured pistons are optimized, and wear, life and thermal imaging tests are performed. Finite element analysis of the friction pair model is performed, and the friction and wear mechanisms are discussed. The results show that the pistons with cylindrical pit arrays have excellent friction and wear performance, less heat generation by friction, longer lives and less scratches on the cylinder liner. The temperature of the optimized textured pistons was reduced by around 5–10 °C. The wear amount of some textured pistons was reduced by over 50%, resulting in an improvement in their lifespan of at least 30% or more. The results of the finite element analysis indicate that the textured piston exhibited reduced deformation and favorable stress–strain distribution and satisfied the required contact pressure.

Autonomous Underwater Vehicles (AUVs) are high-end marine equipment. In turbid, dimly lit waters that require high concealment, traditional methods struggle to detect targets effectively. Fish, however, can accurately perceive nearby targets using lateral line systems even in harsh environments. This provides inspiration for intelligent detection in AUVs. In this study, the flow field cloud around copepods and visualization of pressure difference matrix are analyzed. A method combining the pressure difference matrix and residual neural network regression is proposed to study how fish lateral lines perceive the direction of cruising copepods. Furthermore, the effects of three key parameters on direction perception are discussed, including perception time scale, initial vertical distance and training angular intervals number. The results indicate that most predicted directions are close to the true directions, with only a small number of misjudgments occurring in the vicinity of the opposite or perpendicular directions to the true direction. Moderate perception time scales (100 ms), shorter vertical distances (2.5 mm), and reasonable training angular intervals number (24 or 36) all lead to lower perception error. This study provides a quantitative analysis of fish lateral line perception mechanism, offering valuable theoretical guidance and technical support for intelligent detection in AUVs. • A method combining pressure difference matrix and Resnet regression is proposed. • Perception mechanism of cruising copepods by fish lateral line is studied. • Effects of time, distance and angular interval on perception are discussed. • The results provide bionic inspiration for the intelligent detection of AUVs. [ABSTRACT FROM AUTHOR]