DEVELOPMENT AND VERIFICATION OF MODELING PRACTICE FOR CFD CALCULATIONS TO OBTAIN CURRENT LOADS ON FPSO

Current loads are important input parameters for mooring studies. To accurately predict the motions of moored vessels these quantities should be determined with confidence in the values. Traditionally, these quantities have been determined using model tests in water basins or in wind tunnels. With recent advancements in CFD modeling, the offshore industry has started using CFD as an alternative tool to compute current loads on FPSO's. In order to help adopt CFD as a widely accepted tool, there is a need to develop confidence in CFD predictions. Therefore, a practical CFD Modeling Practice is developed within the Reproducible Offshore CFD JIP. The Modeling Practice describes the geometry modeling, computational mesh, model set-up and post-processing for these types of CFD calculations. This Modeling Practice is verified and validated by five independent verifiers against model test data, such that reproducible and accurate results can be obtained by following the Modeling Practice. This paper provides an overview of the developed Modeling Practice and the calculated CFD results from the verifiers. The CFD Modeling Practice is benchmarked against available model test results for a barge-type and a tanker-shaped FPSO. By following this Modeling Practice, the CFD predictions for CY and CMZ are within 10% from all verifiers and within 10% from the model test results. Larger differences may be obtained for CX, depending on local grid resolution and turbulence model used, but also due to larger experimental uncertainty for this quantity.