Effect of structural parameters on the hydrodynamic performance of vertical curved V-Type otter board *article *

In recent years, the number of vessels entering the Antarctic krill fishery and the amount of catches in China have exhibited an increasing trend. Nevertheless, there is still a gap in the basic research on trawl otter boards for Antarctic krill compared with that of developed countries (Huang et al., 2015). Vertical curved V-type otter boards are common otter boards in Antarctic krill trawling (Matt et al., 2012), which combine the advantages of curved, V-type, and large aspect ratio otter boards (Niedzwiedz & Hopp, 1998). Therefore, they have advantages including convenient operation, strong stability, and easy maintenance (Li, 2012). In order to improve the hydrodynamic performance of vertical curved V-type otter boards, domestic and foreign scholars have conducted a series of related studies to investigate and analyze the operating performance and optimal operating parameters of vertical curved V-type otter boards(Chen et al., 2020; Chu et al., 2020; Liu et al., 2015, 2017, 2018; Sun, 2012; Xu et al., 2016, 2018, pp. 1–378; You et al., 2021). For example, Sala et al. (2009) studied otter boards at sea corresponded poorly with that obtained in the flume tank. Feng and Chen (2001) performed wind tunnel experiments to measure the lift and drag coefficients, moment coefficients, and center-of-pressure position coefficients of V-type otter boards with various sizes at different stroke angles. Mellibovsky et al. (2018) found the trends of in flume tank experiments closely match wind tunnel results. Wang et al. (2004) investigated the parameters affecting the hydrodynamic performance of vertical curved V-type otter boards through wind tunnel experiments. Zhang et al. (2004) investigated and compared the hydrodynamic performance of two types of otter boards, vertical and rectangular curved V-type. Xu et al. (2006) conducted a comparative test on the operational performance and production effect of rectangular V-type curved otter boards and V-type otter boards. Prat et al. (2008) applied the simulation software and have developed a simplified model for bottom trawl fishing gears. The numerical implementation allows for an efficient and consistent coupling among gear components. Zhuang, Xing, Xu, and et al. (2015a, 2015b) performed numerical simulations to visualize the flow regime around the otter board. Liu and Liu (2017) investigated the lift-to-drag ratio and the stability of rectangular curved otter boards by numerical simulations. Xu, Huang, Zhao, and et al. (2017a, 2017b) used two numerical simulation methods to investigate and analyze V-type otter boards with different folding angles and aspect ratios, and found that the hydrodynamic performance was better when the spreading chord ratio was set to 0.49 and the inverse angle was set to 17°.

Previous research on this type of otter boards has mostly focused on the analysis of the hydrodynamic performance of existing structure types. However, not much attention has been paid to the effect mechanism of the structural parameters on the hydrodynamic performance of the otter boards, through which improvement options can be provided (Liu et al., 2020; Wang et al., 2004). To this end, this paper takes a typical vertical curved V-type otter board as the research object, develops a numerical calculation model and a water tank experimental model, and calculates and analyses the parameters related to its hydrodynamic performance. On this basis, the effects of different structural parameters, such as the angle of deflector, arch of deflector, and spacing of deflector, on the hydrodynamic performance of vertical curved V-type otter boards are discussed and analyzed through comparative experiments, and then, a more effective structural design scheme is proposed. The aim of this work is to provide reference for the structural design and optimization of vertical curved V-type otter board.