Effects of the asymmetric riser and bilge keel arrangements on FPSO green water assessment

Abstract

This article aims to report important findings on how the asymmetric riser and bilge keel arrangements affect the motion response and green water assessment by using a real FPSO conversion project. Recently, the authors have proposed a practical approach for short-term and long-term green water prediction. In this paper, the method has been further extended to include the effect of truncated bilge keel by using Morrison elements. Numerical studies are conducted focusing on the effect induced by asymmetric riser arrangement and truncated bilge keels. Comparisons of short-term and long-term results between different models indicate that the FPSO's motion is significantly affected by asymmetrically arranged appendages and attachments in a complicated way. The relative wave elevation is also affected by appendages and attachments, but not the same trend as the motion response. The effect of the asymmetric arrangement of risers and bilge keel on long-term relative wave elevation response has been captured by both traditional contour line approach and response-based analysis, but some discrepancy identified between the results from the two methods indicates the limitation of the traditional contour line approach.

The CFD Investigation of General FPSO Green Water

“…Green water is one of the seakeeping of ships, which is an important index to evaluate ship performance. ABS, DNV, and other classification societies have given different design specifications for floating structures and their equipment [1][2] to ensure the safety of equipment, and the structural safety of bow floating in the process of waves and prevent equipment corrosion and fatigue damage. Although increasing freeboard height and strengthening bow protection can reduce the degree of wave and prevent structural damage, it will also reduce the ship's stability.…”

Influence of bilge-keel configuration on ship roll damping and roll response in waves

“…Their work showed the effect of the generated vortices on the pressure distribution around the mid-section. Wang et al (2019) studied the effects of the asymmetric bilge keel arrangements on the motion response. Numerical studies were conducted focusing on the effect induced by truncated bilge keels.…”