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Propulsion Mechanism Using Hydrofoil Fin with a Variable-Effective-Length Spring - Evaluation of Thrust Characteristics in a Uniform Flow -
Abstract
Since the propulsion mechanism in fluid using an elastic fin, such as the caudal fin or the pectoral fin of fish, is effective. However, the optimum elasticity of the fin is not constant and changes with the movement task and environment, such as swimming speed and oscillating frequency. It is very difficult to exchange fins of different stiffness while the mechanism is swimming.
Thus, we attempted to develop a variable-stiffness fin with a variable-effective-length spring. The apparent stiffness of the spring could be changed dynamically. This fin consisted of a rigid plate, a variable-effective-length spring, and an aluminum box to house the motor for changing the effective length. But the shape of fin was rectangle and far from that of the streamlined fish fin.
As the improved shape of the fin, we have developed the hydrofoil fin with a variable-effective-length spring. We investigated the behavior of an oscillating the fin in a uniform flow, and discussed the thrust force, flow velocity corresponding to the self propelled speed of the fin, thrust efficiency in a uniform flow. Furthermore, we compared these results with those of the previous rectangular fin.References
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DOI: http://dx.doi.org/10.21535%2FProICIUS.2009.v5.548
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