Benchmark Study Between CFD and Model Tests on a Semi-Submersible Crane Vessel

Accurate assessment of current loads on offshore vessels is required to determine operability of heavy lift and pipe lay operations. Whereas in the past only semi-empirical methods or model tests were suitable to obtain these data, CFD has recently become available as engineering tool to assess current loads on offshore structures. CFD has the potential to assess current loads more flexible in a numerical manner. Although the application of CFD has proven its value in assessment of ships resistance and VIV calculations, CFD is still not yet a fully proven method to calculate the current loads on offshore structures. Therefore validation of the results is further required to reach general acceptance of this method for offshore applications. HMC took the initiative to compare and validate CFD results with its model test data of current loads on one of its semi-submersible crane vessels. In this paper a comparison of CFD results with model test data of the current loads of a semi-submersible crane vessel is presented. The CFD calculations are performed as blind computations, so the model tests results were unknown. Afterwards the CFD results are compared with the results of the model tests. Based on both data sets lessons learned are addressed to improve the CFD computations as well as practical aspects and limitations of current load model testing. Furthermore, the possibilities to use CFD to scale the results of the model tests to full scale are explored. Based on this comparison CFD appears to be a complementary, flexible and reliable tool in assessing the current loads on mission critical vessel operations.