Numerical Simulation Of Hydrodynamics Of Carangiform Swimming Based On Flexible Model

In recent years, people have spent lots of efforts in the study of fish-like robotsand the propelling mechanism of fishes for the reasons of its high swimmingefficiency, high speed and high flexibility compared to the traditional submarinepropellers. In the study of fishes’ propelling mechanism, numerical simulation hasbeen used more and more often due to the development of computer science andhydrodynamics theory. The use of numerical simulation method can reach to perfectnatural environment without concerning the experiment conditions and it can beunlimitedly repeated. Although the commonly used commercial CFD software has awide application, it’s efficiency and accuracy are limited. Therefore, aiming torevealing the mechanism of fish propelling, commercial CFD software is abandonedin this paper, and new computing methods are applied into the program coded tosimulate the self-propelling fish.The immersed boundary method is a finite difference method using thestructured mesh, by applying a feedback force into the virtual boundary, theboundary can reach to a no-slip condition. Ignoring the remeshing progress, themethod has a higher efficiency and accuracy. In this paper a numerical method baseon the immersed boundary method is presented and used to computing the velocityfield, pressure field and the feedback force. Simulation of fluid around stationaryand oscillating cylinder is processed to validate the method and codes.Kinematics model and mechanics parameters are established and simulationstudy of a stationary waving fish using the method presented is carried out. Byobserving and analyzing the pressure and vorticity field, the source of propellingforce is investigated. Simulations at different waving parameters such as frequency,amplitude and waving pattern of fish tail are carried out to investigate the effects ofthe parameters to the propelling ability.In order to study the real swimming fish, a self-propelling fish is simulatedusing the methods presented. Established the dynamic fish model and energeticparameters to simulate and study the procedure of fish’s acceleration from zero tosteady speed and the velocity and stress condition at steady swimming is revealed.By changing the waving frequency, amplitude and number of body waves, theeffects of these parameters to swimming abilities are simulated and analyzed.