Abstract
In this study, numerical simulations are employed to investigate the hydrodynamic performance and wake topology of a swimming Rhinoptera javanica. The study is motivated by the quest to understand the hydrodynamics of median and paired fin(MPF) mode with both spanwise and chordwise flexibility. The simulations employ an immersed boundary(IB)-simplified sphere function-based gas kinetic scheme(SGKS) method that allows us to simulate flows with complex moving boundaries on fixed Cartesian grids. A computational model is constructed based on biological data. The evolution of the hydrodynamic force and 3D vortex structures are presented. Besides, the effect of frequency and amplitude are also discussed to explain some behaviors of the actual Rhinoptera javanica. This work can provide a baseline for the design of a bio-inspired underwater vehicle.
Highlights
With the great demand for marine exploration, there is a growing need for the adaptation of robotic systems which can autonomously perform routine tasks in aquatic environments
The thrust force and lift force are presented here as non-dimensional coefficients CT and CL, which were computed by CT, CL = FX, FZ /0.5ρU 2BL2
At f = 0.4 Hz, the peak value increases 200% as the amplitude increase from 0.2 to 0.43, while the increment value at f = 1.3 Hz is 1124%, which indicates that the increment of stroke frequency dominates the thrust increment. It can explain the reason why the frequency of Rhinoptera javanica is generally kept at a large range when they are swimming at high speed in our observations
Summary
With the great demand for marine exploration, there is a growing need for the adaptation of robotic systems which can autonomously perform routine tasks in aquatic environments. To improve the efficiency and endurance of underwater operation, it is indispensable to reduce the travelling resistance and increase the propulsion efficiency and maneuverability of the vehicle. It is not difficult to obtain a shape with excellent resistance performance [1] by using CFD, experimental means and various optimization techniques. The traditional propulsion and control system with propeller and rudder has a propulsion efficiency of 70% - 80%. How to further improve the propulsion and control efficiency becomes another big problem. It is difficult to meet the above requirements through continuous optimization
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