| Fishing gear’s hydrodynamic performance is one of the main indicators to measure its operating performance. Ropes constitute the skeleton and the basic structure of net fishing gears and other facilities, which suffered the hydrodynamic determines the shape and performance of fishing equipment and other facilities. Hydrodynamic characteristics of the ropes is the important part in study of fishing gears. Because the rope is relatively soft, and its three-dimensional structure of the special nature make it difficult to measure. Its hydrodynamic parameters research requires precise experimental design and measurement equipment. This led to research in this area is still very rare.This article is intended to draw hydrodynamic coefficients of three-strand polyethylene rope and develop a preliminary research on three-dimensional numerical simulation in the flow field. It will provide references for the three-dimensional numerical simulation of rope in the future.Firstly, hydrodynamic experiment of three strand polyethylene rope developed in dynamic sink, and drag, lift force and lateral force of three strands in unit length at different impact angles are measured, through theoretical analysis, the drag coefficient, force coefficient and lateral force coefficient are rise in Re=2.5 X 103-3 X 104. The results show that:(1) The length of the rope and the velocity of the rope under the condition of three experimental angle are two times of the velocity, which is in line with the Morrison equation.(2) The drag force of unit length twine and the square of current speed show a good linear relationship, the correlation coefficient is larger than 0.99, which is in agreement with the Morison equation,(3) Lift force is same to (2) at the attack angel=45°and60°;(4) Changes in the lift coefficient and drag coefficient of the trend is similar in 1.2 × 104 <Re<3 × 104 range fluctuate at a certain constant value;(5) a small lateral force is present, lateral force coefficient between-0.15 to 0.15.Then, based on computational fluid dynamics theory, based on platform of computational fluid dynamics software FLUENT,with three-dimensional turbulence simulate technology, the model of the three-stranded polyethylene rope carried out numerical simulation of hydrodynamic performance. It shows the drag force of different diameters and different twist three-stranded polyethylene rope in the above velocity and inclination, and the calculated results are compared with experimental data in order to use the simulation method reveals three-stranded polyethylene rope’s hydrodynamic performance in the flow field. After comparing the results, we find analog is better when the angle is 90 °. The relative error between simulated and measured value in the tank experiments is in the range of 0.76%-30.98%. The research show that the numerical simulation results are consistent with hydrodynamic characteristics of three-stranded polyethylene rope in unsteady flow field when a certain velocity and the attack angel under this method.Finally, we summarize the reasons for the gap between numerical simulation and the expected. It will provide some useful reference for future research. |
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