Experimental Study on Resistance Characteristics of Three-Stranded Polyethylene Twines in Flow

Three-stranded polyethylene twine is one of the basic materials for woven mesh. It is popularly used to make net wing, net body, cod-end etc. The water resistance of the twines plays an important role in the shape and performance of these fishing gears. A testing device was designed to measure the hydrodynamic properties of twines, which is fixed on the towing carriage. The water resistance is m easured for five types of twines with the attack angle equal to 90° and the towing speed is set within the range of 0.2m/s- 1.6m/s. The results of the present study may provide basic parameters for the theoretical calculation and numerical simulation of meshes, netting gears, sea cages or other fishery facilities. It can be obtained the following results through data analysis. At all the testing speeds, the drag force per unit twine length is proportional to the square of towing speed. The correlation coefficient is larger than 0.99, which is in agreement with the Morison equation. Drag coefficient shows a slowly decreasing trend as the Reynolds number is within the range of 3.5×10 2 ~ 6.0×10 3 . It can be expressed in a power function 051 . 0 291 . 2   d R Cx