The kinematics and performance of zebrafish C-shaped maneuvering

It is difficult to obtain the complete kinematics and hydrodynamics from the experiments in the study of fish C-type fast-start, which can be divided into C-start and C-turn by the duration of maneuvers. Using high-speed photography, a series of top-view images of zebrafish's C-shaped maneuvering were obtained on the self-built platform based on machine vision. A simplified three-dimensional (3D) fish model was established according to the outline and midline of the fish body extracted from the images by using a mathematical morphology algorithm. Then, due to the conservation of the linear and angular momentum, the complete kinematic and hydrodynamic data during the whole maneuver motion can be obtained and the translational and rotational energy can be distinguished from the total kinetic energy of the zebrafish body. The modification of the caudal fin length is a highlight in 3D modeling, which is based on the equivalence of the area second-moment of a flapping 3D plate. Through the benchmark validation, the maximum geometric error of the digital image processing is less than 3.1%. The results show that the maximum acceleration in all the C-type fast-start is linearly related to the maximum angular acceleration, and the rotational energy of C-turn is dominant in the kinetic energy while the translational energy of C-start is dominant.