레이놀즈 수가 와류 감쇠 및 저항 저감형 나선형 해양 구조물 주위 유동에 미치는 영향
Reynolds number effects on flow over twisted offshore structure with drag reduction and vortex suppression
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We investigated the Reynolds number effects on the flow over a twisted offshore structure in the range of 3×10³≤Re≤1 ×10. To analyze the effect of the twisted surface treatment, a large eddy simulation (LES) with a dynamic subgrid model was employed. A simulationof the cylindrical structure was also carried out to compare the results with those of the twisted offshore structure. As Re increased, the mean dragand lift coefficient of the twisted offshore structure increased with the same tendency as those of the cylindrical structure. However, the increasesin the mean drag and lift coefficient of the twisted offshore structure were much smaller than those of the cylindrical structure. Furthermore,elongated shear layer and suppressed vortex shedding from the twisted offshore structure occurred compared to those of the cylindrical cylinder,resulting in a drag reduction and suppression of the vortex-induced vibration (VIV). In particular, the twisted offshore structure achieved asignificant reduction of over 96% in VIV compared with that of the cylindrical structure, regardless of increasing Re. As a result, we concludedthat the twisted offshore structure effectively controlled the flow structures with reductions in the drag and VIV compared with the cylindricalstructure, irrespective of increasing Re.
Abstract
We investigated the Reynolds number effects on the flow over a twisted offshore structure in the range of 3×10³≤Re≤1 ×10. To analyze the effect of the twisted surface treatment, a large eddy simulation (LES) with a dynamic subgrid model was employed. A simulationof the cylindrical structure was also carried out to compare the results with those of the twisted offshore structure. As Re increased, the mean dragand lift coefficient of the twisted offshore structure increased with the same tendency as those of the cylindrical structure. However, the increasesin the mean drag and lift coefficient of the twisted offshore structure were much smaller than those of the cylindrical structure. Furthermore,elongated shear layer and suppressed vortex shedding from the twisted offshore structure occurred compared to those of the cylindrical cylinder,resulting in a drag reduction and suppression of the vortex-induced vibration (VIV). In particular, the twisted offshore structure achieved asignificant reduction of over 96% in VIV compared with that of the cylindrical structure, regardless of increasing Re. As a result, we concludedthat the twisted offshore structure effectively controlled the flow structures with reductions in the drag and VIV compared with the cylindricalstructure, irrespective of increasing Re.
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