Session: 06-16-03 Wave Mechanics, Modeling and Wave Effects III

Paper Number: 80038

80038 - Interaction Effects of Weakly Nonlinear Surface Waves and a Vertically Sheared Current on Loads on a Vertical Cylinder 

In coastal regions surface gravity waves and subsurface currents widely coexist and their interaction can considerably affect their ambient environments. The focus of this work lies in their effects on loads on offshore slender structures. As is known, a background current can alter the main properties of surface waves. For example, the effect of Doppler shift on the dispersion relation due to a nearly uniform flow and it was found in recent works that refraction to waves can attribute to the velocity profile of a shear current in both the vertical and horizontal direction. The latter has been rarely examined, if not none, on the loads on offshore slender structures, admitting that attentions of the effects of a shear flow have been attracted in other important aspects, e.g. the vortex induced vibration. This paper employs a semi-analytical model which allows for three-dimensional weakly nonlinear surface waves in a vertically sheared flow without the assumption of irrotational flows. Based on this model and a modified Morison equation, we examine roles of the velocity profile of a shear current on loads on a vertical cylinder in different sea states through the comparisons between cases in the presence and absence of the current. The results would be in particular of high relevance to offshore man-made structures (e.g. fish cages, risers, mooring lines, and monopolies) in coastal regions, e.g., Norwegian fjords and off the coast of Scotland, where a background flow is strong in both the velocity magnitude and the profile shear.

Presenting Author: Zirui Xin State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University

Authors:

Zirui Xin State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University
Xin Li State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University
Yan Li Department of Energy and Process Engineering, Norwegian University of Science and Technology; Department of Mathematics, University of Bergen