振動する正方形断面柱に作用する変動流体力特性 : 一定の振幅角で回転振動する場合

概要

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Measurements were presented of the time-averaged and fluctuating fluid forces and the vortex shedding frequency on a square-section cylinder forced into rotary oscillation with constant frequency and amplitude. The cylinder's Reynolds number was 3.7×10^4. The cylinder was forced into rotary oscillation at angular displacements up to α=±10°and the non-dimensional frequency F^*B/U (F : frequency of forced oscillating cylinder, B : width of cylinder, U : free-stream velocity) was varied from 0.04 to 0.23, in which the lock-in region was included. It is found that the frequency of vortex shedding from the oscillating cylinder tends to be equal to n times the cylinder oscillation frequency. Also, within the lock-in region in which the vortex shedding is perfectly synchronized with the forcing frequency F^* of the cylinder only, the time-averaged and fluctuating fluid forces are found to reach a maximum at a certain critical frequency. Furthermore, it is recognized that the fluctuating moment induces the generation of negative aerodynamic damping since the work done by the force is almost always positive in the lock-in region.
1993-06-25