Wave current interaction: Effect on force prediction for fixed offshore structures

Mohamed Latheef,Nasir Abdulla,Mohd Faieez Mohd Jupri,M Raza Ul Mustafa,M Latheef,D Bayu Endrayana,I Bin Othman,N Zulaikha Bt Yusof

doi:10.1051/matecconf/201820301011

Mohamed Latheef, Nasir Abdulla + Show 6 more

Open Access

https://doi.org/10.1051/matecconf/201820301011

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Abstract

MetOcean conditions in the South China Sea (SCS) indicates that unlike other locations such as the North Sea, the magnitude of the currents can be relatively large. In addition, these currents are strongly sheared. The present study focused on the typical design problem of calculating the ultimate base shear and overturning moments for slender fixed structureswiththe inclusion of the interaction between the currents and the wave field. It has been found that the loads on average can be around 15% larger when this interaction is accounted for in the calculation of the loads, highlighting the importance. In addition, the level of these amplifications were found to be dependent on the sea state steepness and the relative water depth. While no clear trend was found (changed case by case) in the present work, incorporating the vertical structure of the current was found to change the pattern of the amplification of the loads.

Highlights

IntroductionAs [1] noted, a full description of the flow field that takes into account the interaction between the waves and the current is never undertaken in the design of either coastal or offshore structures
In the ocean, waves never exist without an associated current
The calculation of the total base shear using M2 and M3 leads to larger loads compared to the simplified procedure of using the Stokes’ 5th order solution (M1) with no consideration of wave–current interaction, ranging from around 5% to as high as 500%

Summary

Introduction

As [1] noted, a full description of the flow field that takes into account the interaction between the waves and the current is never undertaken in the design of either coastal or offshore structures. The present study will be limited to the regular wave loading on fixed slender offshore structures comprising of tubular members. A tubular member is considered as slender when the diameter to wave length ratio, D/λ ≤ 0.2. For this regime, after [2], the force per unit length, fT , is expressed by the sum fT = ρC M A ∂u ∂t + D Du|u|,

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