2023 年 69A 巻 p. 262-269
This paper experimentally investigates the effects of side-surface openings on the torsional flutter instability of a rectangular cylinder with a side ratio of B/D = 5, where B is the width and D is the height. The torsional one-degree-of-freedom (1DOF) free vibration tests and flow visualization tests were carried out on the rectangular cylinder with different-sized openings. The opening size is non-dimensionalized as the Opening-area Ratio (OR), which is the ratio of the total-openings area to the sidesurface area. Increasing OR stabilized the rectangular cylinder against the vortexinduced vibration and the torsional flutter and promoted the separated shear layer to reattach more upstream side of the cylinder surface. This research contributes to providing a method to stabilize the box girder against torsional flutter.