| 研究実績の概要 |
Problem (1), single flag-type energy harvester: Based on an energy balance considerations we have analyzed (a) the physical mechanism of flutter in a mathematical model of a flapping flag and (b) the stabilizing - or destabilizing - effect effect of dynamically varying fluid forces, expressed via the complex Theodorsen function, as opposed to the quasisteady approximation. The energy balance analysis shows that (a) it is necessary for the flag/plate to perform a `dragging' type of flutter motion, similarly, in appearance at least, to the motion of a swimming eel, and (b) a small imaginary part of the Theodorsen function has a destabilizing effect, in the sense that the critical flow speed is smaller than by the quasisteady approximation. These predictions are verified by numerical eigenvalue analyses. This is in opposition to previously reported results, which have not traced the eigenvalue branches. The importance of tracing the eigenvalue branches is thus emphasized.
Problem (2), a system of many interacting flag-type energy harvesters: we have studied such a system where the flags were modeled as 2 degrees-of-freedom plates and where the flow was modeled by a discrete vortex method. Flags arranged in a triangular formation were found to develop high-amplitude oscillations and may be a good candidate for an energy-harvesting system.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
Problem (1): As mentioned in "Summary of Research Achievements" there are unclear points in the basic theory, so rather than to start directly on shape optimization, I have spent time on investigating the basic theory.
Problem (2): Convergence of the analysis by many interacting flags has been a challenge and time-consuming; but there has been progress as well.
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| 今後の研究の推進方策 |
The theoretical/experimental work will be continued in accordance with the original plan.
A small wind-tunnel, as well as a water-tunnel, has been installed in the laboratory. (These items have been donated by a retiring Prof. from the Inst. of Fluid Science, Tohoku Univ., Prof. Masami Nakano.) These items will be employed to carry out experimental verifications of the predicted results.
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