LOW REYNOLDS FLOW PAST A CIRCULAR CYLINDER CLOSE TO A FREE-SURFACE WITH VERTICAL MOTION DYNAMICS

摘要

Flow past a circular cylinder close to a free surface at low Reynolds number is investigated numerically in this paper extending the work done in previous 2014 and 2015 OMAE papers. In the former, the dependence of the flow with the submergence was discussed and in the latter the flow at high Froude numbers was investigated. It was found that shedding is blocked as the cylinder approaches de free surface with an increasing value of the net lift coefficient and a reduction of the lift alternate oscillations due to such shedding. This variation on the lift pattern suggests that if a VIVACE device is set under these flow characteristics, its performance will significantly differ from that in deep water conditions. These devices take advantage of flow induced motions in bluff bodies (such as the cylinder) to generate electric power. Singh & Mittal coupled VIV system is studied in present paper in the presence of a free surface, selecting a configuration with large response in unbounded flow and adding a free-surface to such case. Results are presented and discussed.