Evaluation of scale effect on hydrodynamic force of V-shaped otter board based on CFD

The main way to study the hydrodynamic characteristics of the otter board is to build a physical model to measure its hydrodynamic characteristics based on the similarity law. In this study, we analyzed the lift, drag coefficient and flow field distribution of V-type otter board with three scale ratios (1∶2, 1∶3 and 1∶4) and three thickness (2, 5 and 10 mm), then we compared them with the corresponding model test results to explore the influence of different physical model scales on hydrodynamic estimation of the otter boards. The results show that: 1) With the increase of the angle of attack, the drag coefficient of otter board with all scales gradually increased, while the lift coefficient first increased and then decreased, and the lift-drag ratio decreased gradually. 2) When the angle of attack reached 30°, the apparent separation vortex appeared at the back of the otter board, resulting in the decrease of simulated lift force. 3) With the increase of the otter board model scale, the separation effect of the boundary layer on the otter board surface and the separation vortex of the flow field in the wake area increased gradually, and the lift, drag and lift-drag ratio of the otter board also showed an increasing tendency. The thickness of the mesh plate had little effect on the flow field, lift and resistance, and the average error of the maximum lift coefficient relative to the model test was 4.97%. As the model scale increased, the prediction error of hydrodynamic force decreased gradually.