Производительность сил траловой системы – IV: математическое моделирование (часть II)

Abstract

The rope-net tools of commercial fishing are mostly engineering structures that change their shape during operation. So, when changing the towing speed of a mid-water trawl, a redistribution of forces occurs, created by the equipment and the trawl shell, which leads at low speeds to an increase in the opening area of the mouth of the trawl, and at high speeds to a decrease in the area. Accordingly, the greater the hydrodynamic resistance of the rope-net part of the trawl, the greater the forces that pull together its rope-net part, and vice versa. Force is a value that is a measure of the impact on the mid-water trawl by other elements of the trawl system (TS) and the environment external to the TS. The application of force causes a change in the speed of the mid-water trawl and the appearance of deformations and mechanical stresses in steel ropes (SC) (warps, legs of trawl boards, cables, bare ends, rebounds) and rope-net products (RNP) (rope ties, elements of net plates). Deformation can occur both in the vehicle itself and in the elements fixing it. Then the trawling performance indicator, which determines the characteristics of the fishing activity of the vessel, is the ratio of the output of the product to the resources spent on it. The article deals with the problem of elongation of ideally flexible SC and RNP. It should be noted that when elongated, their length and diameter change and, accordingly, the hydrodynamic drag coefficient of the rope-net shell of the trawl changes, and the wear of products also increases. The authors obtained equations for ideally flexible SC and RNP, which relate the structural, geometric and power characteristics, provided that the volume of steel ropes and rope-net products does not change, and expressions for determining the relative deformations in the longitudinal and cross sections of steel ropes and rope-net products at their stretching.