Numerical and model experiments to study the hydraulic head of complex engineering mesh structures

This article examines the results of a comprehensive study of the simulation modeling of hydraulic head in complex engineering mesh structures, such as trawl bags. The relevance of the study is stipulated by the need to optimize the hydrodynamic characteristics of fishing gear to minimize the energy consumption of a fishing vessel. During a series of physical experiments with scale models of trawl bags, simulation models have been developed based on the data obtained. They describe in detail the complex structure of water currents both directly inside the net construction itself and in the surrounding water space. The models under study fundamentally differ from each other in key design characteristics: the cord area varies from 0,89 to 1,49 m², solidity — from 0,10 to 0,29, and hanging coefficients are 0,18≤ u x ≤0,33 and 0,94≤ u y ≤0,98. At the same time, the diameter of the net cord remains strictly constant for all samples and is 3,1 mm. The numerical experiment has been conducted using precision computer modeling in the specialized software environment “Modeling of the mesh engineering structures taking into account external influences”, developed by the Department of Commercial Fisheries of FSEI HE «KSTU». The variable factor in the hydrodynamic attack is the spatial orientation of the mesh fabric, which has been studied in two orthogonal projections: T0 and T90. Analysis of the obtained data has made it possible to identify a nonlinear relationship between the hydrostatic head coefficient and the combined influence of structural permeability and the flow attack angle. Changing the orientation of T0 and T90 while maintaining continuity statistically significantly alters the hydrodynamic resistance, which is extremely important for designing energy-efficient trawl complexes. The resulting simulation models have high predictive accuracy and can be extrapolated to full-scale fishing facilities. The results of the study make a significant contribution to the development of the theory of designing flexible permeable barriers and make it possible to optimize fuel consumption in trawl fishing.