IB-LBM Numerical Modeling Of A Tadpole Swimming

Swimming of creatures has characteristics of high efficiency, rapid mobility and low noise through the natural selection. In the study of fluid mechanics, swimming has always been the hot spot, and the swimming of tadpoles is a special one. A Tadpole lives in low Reynolds number environment and can change its body when transforming into a frog.The tadpoles can sense their environment changes by their lateral line system, and they can change their form of swimming in order to reduce energy consumption and to enhance the efficiency of the propulsion with the aid of the surrounding fluid.The new model established in this article employs immersed boundary-lattice Boltzmann method for complex environment of tadpoles of flow field in a two-dimensional numerical simulation and lattice Boltzmann method is utilized to construct fluid field and immersed boundary method is used to simulate the interaction between tadpoles and fluid. Firstly, we establish the model of a tadpole shape, and put axial bending moment on the tail to provide motivation for swimming. Then we use the new model to study the tadpoles hydrodynamics characteristics of propulsion, especially how factors including obstacle, wall wave number, amplitude, frequency and length affect the performance of tadpoles propulsion, and validate the results by conducting experiments. The conclusions can are the following.(1) The obstacle and the wall will affect the swimming. Tadpoles around the obstacle can swim along the barrier according to the change of stress in the surrounding flow field, and then leave the obstacle at some place. Tadpoles in the vicinity of a wall will keep swimming in a stable linear state for a period of time, and then leave the wall. This means the phenomenon that tadpoles swim bypass the obstacle and move forward in the previous direction or adhere to the wall is a kind of active control.(2)The change of the wave number will influence the swimming. In a certain range, the larger wave number is, the more swimming efficiency increases, as well as the oscillation amplitude decreases.(3)The amplitude and frequency are important factors in swimming. With the increase of the tail amplitude, the tadpole tends to swim faster, and the oscillation amplitude of its body becomes larger. As well, the larger frequency is, the faster the tadpole is.(4)The length of the tail is an important variable in the physical model. It can be concluded that the shorter tail the tadpole has, the faster it is, and the oscillation amplitude becomes larger. It fits well with the experiment.