Journal
OCEAN ENGINEERING
Volume 233, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.oceaneng.2021.109112
Keywords
Bottom trawl; k-omega shear stress turbulent (SST) model; Acoustic Doppler velocimeter; Large deformation non-linear structural finite; element model; Velocity reduction; Hydrodynamic forces
Funding
- National Natural Science Foundation of China [31902426]
- Shanghai Sailing Program [19YF1419800]
- China Postdoctoral Science Foundation [2018M630471]
- Luo Zhaorao Science and Innovation Fund [A1-2004-20-201302]
- Ministry of Agriculture and Rural Affairs [D-8002-18-0097]
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The hydrodynamic performance of a scaled bottom trawl model in current was investigated using numerical simulations and flume tank tests. Both the numerical and experimental results indicated that increasing mesh size and decreasing twine diameter significantly reduced drag force. The study also observed the spatial development of turbulent boundary layer flow and vortex shedding in the trawl wake.
In this work, the hydrodynamic performance of a scaled bottom trawl model in current was investigated by using numerical simulations based on the fluid structure interaction (FSI) method in two-way coupling and the flume tank test based on modified Tauti's law. In this numerical model, a finite volume approach was used for solving the Navier-Stokes equations combined with a k-omega shear stress turbulent (SST) model for describing the flow. A finite element approach was used for solving the large deformation nonlinear structural dynamic equation to describe the trawl net configuration and the nodal displacement. A series of flume tank tests was conducted on three scaled bottom trawl models with different twine diameters, twine materials, and mesh sizes. In addition, three-dimensional (3D) Acoustic Doppler Velocimeter (ADV) measurements were performed to experimentally investigate the effect of turbulent flow on the bottom trawl net performance. The comparisons showed that the numerical results were in good agreement with the experimental data. Both the numerical and experimental results indicated that the increase in mesh size using Dyneema multifilament and the decrease in twine diameter using nylon monofilament led to decrease in the drag force by about 2.1 times and 2.2 times, respectively (p < 0.002 ANCOVA test). It was found that there was spatial development of turbulent boundary layer flow around the trawl net and the vortex shedding in the trawl wake. In addition, the equivalent stress, elastic strain, and total deformation increased with the increase in flow velocity and, mesh size, and the decrease in twine diameter.
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