Preliminary design and hydrodynamic study of power-driven float pole system in Pacific saury fishery

Abstract

Pacific saury (Cololabis saira), an essential commercial fish species in the North Pacific Ocean, is captured primarily using the stick-held dip net (SHDN) method. During the netting process, the separation of the gear from the vessel is dependent on the wind and currents, which represents a passive operational approach. In this study, we designed a prototype power-driven device for SHDN gear. The device consists of two thrusters, a remote-control system, and an energy device. It was installed on a 1/10 length segment of a float pole, hereafter referred to as the power-driven float pole (PFP) prototype. Experiments were conducted on both the single-thruster and PFP prototype to investigate the relationship between their rotational speed and thrust. SolidWorks was used to model the single-thruster and PFP prototype, and Ansys Fluent was used to solve the Reynolds-averaged Navier–Stokes equations to obtain the hydrodynamic characteristics of both the thruster and PFP prototype. A comparative analysis of the experimental and simulated hydrodynamic results showed the following: (1) the flow velocity between the blade suction surface and pressure surface tended to decrease, and the pressure tended to increase; (2) the thrust of both the single-thruster and PFP prototype increased with the thruster rotational speed according to a quadratic polynomial relationship; (3) the thrust ratio between the PFP prototype and the combined thrust of the two thrusters under the no-load condition exhibited a logarithmic relationship with the increasing rotational speed; and (4) to meet the operational requirements of the PFP prototype with a working duration exceeding 350 min and a minimum thrust of 20 N, the recommended rotational speed range for the thrusters on the PFP prototype was 1569–1970 rpm. The results of this study provide a fundamental reference for the further optimization of the PFP configurations.