3219 円柱構造物の流力振動 : 回流水槽による 2 次元模型実験結果

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Flow-induced in-line oscillation of a circular cylinder was experimentally studied by free-oscillation tests in a water tunnel. Response amplitudes of a circular cylinder were measured for smaller values than 1 of the reduced mass-damping parameter (the so-called Scruton number). In the free-oscillation tests, cylinder models were spring-mounted so as to oscillate as a rigid cylinder in water. Although the water flow has the turbulence intensity of about 3%, two excitation regions appear around a half of the resonance velocity. We found a hysteresis phenomenon of response amplitude in the in-line oscillation. The response amplitude are sensitive to the reduced mass-damping parameter during the in-line oscillation with a symmetric vortex street in the first excitation region, and the alternate vortices are periodically shed, locking-in with the vibration of a cylinder in the other region.
2000-07-31