Experimental Study Of Unsteady Locomotion And Swarming In Zebrafish

Researches on the biomechanics related to fish swimming have the vital scientific significance and important application. The problem itself contains much of uncovered mechanism, and the research results can guide the development and manufacture of new high performance underwater vehicle. Undulating swing is the primary propulsion mode used by most of the fish, and study of this phenomenon plays an important and basic position. Recent advances in the diversity and precision of research methods and techniques lead to more attention to the distinction between swimming mode, interactions between various parts of the fish or fish school, and active control of fluid around by the swimming fish. As an active interdisciplinary research field, study of fish swimming also promote the development of related disciplines, such as biology, materials science and control theory.The present investigation focuses on the Zebrafish (Zebra danio), a tropical species of freshwater fish, which contains the kinematics and hydrodynamics studies on S-Start maneuvers, burst-and-coast swimming and turning maneuvers, swimming of fish larvae and fish school.Firstly, the kinematical characteristics are obtained by observing the zebrafish S-starts. Rrcorded by using a high-speed video. The velocity and acceleration of the zebrafish are derived from the raw distance-time data. The mechanism of zebrafish S-starts is analyzed by using the Weihs’ model (the improved large-amplitude elongated-body theory), yielding the forces, moments and turning angular accelerations acting on the zebrafish. This thesis analyzes the hydrodynamics of S-starts and the influence factor in the different stage of the S-starts, and explains the kinematics of fish S-starts from the point of view of hydrodynamics.Secondly, by using two-dimensional digital particle image velocimetry (2D-DPIV), burst-and-coast swimming and turning maneuvers of zebrafish were investigated and clarified the differences in flow structure between zebrafish and koi carps, the reason for the differences was explained. In the studies on burst-and coast swimming, the differences in flow structure between the multiple tail-beat mode and the half tail-beat mode were distinguished. Calculated Results of the drag coefficient ratio of burst-and-coast and the average impulse pointed out that35%of energy is saved when burst-and-coast swimming is used by zebrafish compared with steady swimming. In the studies on turning maneuvers, zebrafish is able to control the direction of jet to maximize the torque so as to improve the turning efficiency.Thirdly, based on the optomotor response of zebrafish, the experimental system was designed for investigating the effect of zebrafish motion drived by moving grating. Meanwhile, the zebrafish school was carried on a simple induction.Finally, swimming of zebrafish larvae was studied by experimental and numerical method. According to velocity of Zebrafish, the swimming of Zebrafish larvae can be divided into3modes:accelerated motion, and decelerated motion. The duration of uniform motion will decrease with the growth of the Zebrafish body. The dynamics of Zebrafish larvae swimming had been studied by numerical method either.