No abstract

The paper proposes a fast method for rebuilding a three-dimensional computational grid for problems of modeling hydrodynamic fields in trawling systems during sound ranging at runtime using a hardware rasterizer of a graphics processor. When the position of a streamlined object changes, it is necessary to periodically update the boundary conditions at the grid nodes near its surface, which, in case of three-dimensional statement, is a laborious task. The suggested method allows a multiple acceleration of the grid update process compared to software implementations. The essence of the method lies in implementation of the pixel shader of the graphics pipeline during rendering, namely, the possibility of outputting the grid nodes into a 3D buffer taking into account information about Z-coordinate of a pixel and a velocity vector of a surface point. The method has been approved using a computer program developed on its basis. The method can be applied both in calculating the influence of hydrodynamic fields on propagation of acoustic waves, and in other applications.

The article considers the problems of physical modeling of twisted filamentary parts of fishing gear and the similitude rules of bending stiffness of filamentary gear parts (FP). The problems are caused firstly by the scope, high costs and complexity of engineering structures in commercial fishery, and thus it was impossible to use them in full-scale testing. Secondly, the lack of systematic experiments prevented from measuring the bending stiffness of synthetic rope parts of fishing gear (SRP). Thus, it becomes necessary to conduct model experiments related to physical modeling of dynamic processes occurring in twisted fishing gear, as well as to carry out a detailed study of the theory of similarity. An attempt to evaluate the bending stiffness of a full-scale object made of polyamide (diameter = 10 mm, the object length and pin diameter were found using large-scale physical characteristics) based on the analysis of experimental data on bending stiffness of synthetic filamentous gear parts made of polyamide with different diameter and length (length = 0.08; 0.10; 0.12; 0.16; 0.20, 0.24 m and diameter = 1.10; 2.0; 3.10; 4.0; 5.0, 6.0 mm) defined on the pins with diameter = 2.0, 10.0 and 30.0 mm. The obtained data will help to prove the correctness of using the theory of dynamic similarity in the course of justification of similarity rules of bending stiffness of the large-diameter cordage and to determine the basic physical and mechanical properties necessary for modeling industrial fishing gear.

The article focuses on the problem of physical modeling of the physical and mechanical properties of fishing twisted filamentary materials, in particular, the most important one – the breaking load. The problems arise because of conducting full-scale experiments, particularly when the ropes of large diameter are used to build the rope parts of fishing gear. The solution to the problem of determining the breaking load on filamentary parts can be found by using specialized tensile testing machines and modern software, which is an effective tool for predicting the reliability and a resource of a gear part operating in difficult conditions of dynamic and shock loads. However, de-signing of fishing gear must begin with large-scale modeling, which will help to correctly calculate the physical and mechanical properties of the designed object using the well-known parameters of the full-scale material. The similarity rules of breaking load of fishing twisted filamentary gear used for the construction of industrial fishing tools will make it possible to model new elements of these tools without conducting full-scale experiments. At the same time, they will already contain solutions to problems associated with studying the dynamic processes, deformation, fracture, as well as the prediction of reliability and resource of the material. The technique proposed based on determining the scale of similarity of filamentary gear made of polyamide fibers, will help to simu-late various net and rope elements from filaments gear of various sizes and structures, instead of conducting energy-intensive experimental studies on ropes of large diameter.

An important task of mechanics of synthetic fishing twisted rope and string products and braided cords is to create a fundamental basis for describing their fracture processes during deformation in operation, i.e. to develop a framework for fracture mechanics (building models and algorithms for calculating structures and technological processes at large plastic deformations, taking into account fracture). There is considered the necessity of developing and introducing the simple and at the same time effective criteria of destruction, allowing to estimate reliably the conditions of safe operation of twisted rope and string products, threaded products and braided cords and especially the structures of industrial fishing gear. Determination of stress concentrations, is an obvious task in connection with the creation of new fishing trawls, purse seines and grips with complex shape-changing geometry. This problem is actual for many branches of industry, including transport and machine-building, where at the designing stage it is necessary to take into account possible emergency situations caused by intensive dynamic effects in twisted rope and string, threaded products and braided cords. Components and structures of twisted rope and string products, threaded products and braided cords should withstand the specified loads in a wide range of loading rates. In particular, the theory allows to solve nonlinear problems, taking into account changes in geometry of deformable twisted rope and string products, threaded products and braided cords, as well as to obtain analytical solutions of various problems.