굽은 형상을 가지는 라이저 주위 유동 특성에 관한 연구

Abstract

The flow around a curved riser, which is exposed to the current in various directions, was investigated at Reynolds number of 100 using numerical simulation. The present study shows that the flow features of the curved riser are distinct from those of the straight riser due to its large radius of the curvature. Namely, there are various wake patterns according to the flow incident angle. As the incident angle increases from 0 to 90, two-row street of vortices developed alongthe centerline of the curved riser becomes more apparent. However, when the incident angle approaches 180 from 90, these vortices are completely suppressed by an interaction between the wake and an axial flow induced by the curvature of the riser. To identify this feature, the sectional force coefficients were also considered, which is quite different to the force coefficients using from 2D strip theory to investigate vortex induced vibration. As a result, for realistic estimation of the riser VIV and a fatigue life, this type of study will be important, and new force coefficient DB including three-dimensional effect should be established.