Emulating the fast-start swimming performance of the chain pickerel (Esox niger) Using a mechanical fish design
Watts, Matthew Nicholas
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Mean maximum start-up accelerations and velocities achieved by the fast-start specialist, northern pike, are reported at 120 m/s sq and 4 m/s, respectively (Harper and Blake, 1990). In this thesis, a simple mechanical system was created to closely mimic the startle response that produces these extreme acceleration events. The system consisted of a thin metal beam covered by a urethane rubber fish body. The mechanical fish was held in curvature by a restraining line and released by a pneumatic cutting mechanism. The potential energy in the beam was transferred into the fluid, thereby accelerating the fish. The fish motion was recorded and the kinematics analyzed while using a number of different tail shapes and materials. Performance of the mechanical fish was determined by maximum acceleration, peak and averaged maximum velocity, and hydrodynamic efficiency. Maximum start-up acceleration was calculated at 48 m/s sq. Peak and averaged maximum velocity was calculated at 0.96 m/s and 0.8 m/s, respectively. The hydrodynamic efficiency of the fish, calculated by the transfer of energy, was 11%. Flow visualization of the mechanical fast-start wake was also analyzed. The visualization uncovered two specific vortex-shedding patterns; a single and a doublevortex pattern are described.
CIVINS (Civilian Institutions) Thesis document
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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