Shallow Water Current Loads on a LNG Carrier Using CFD

To determine shallow water effects on current loads for an LNG Carrier, CFD calculations with MARIN’s CFD code ReFRESCO have been carried out. The CFD results are compared to model tests carried out in MARIN’s Shallow Water Basin for the HAWAI JIP. The loads have been determined for three different water depth to draft ratio’s, from relatively deep water to shallow water. For all water depths the difference in CY coefficient between the CFD results and experiments is 5–10%. Furthermore, the blockage effects from basin side walls are investigated. For shallow water it was found that the blockage effects are significant, i.e. 30–50%, and that they vary for different current headings. For deeper water the blockage effects are smaller than 5%. The influence of “towing” versus a “current” flow situation is also studied. In the experiments the model is towed through the basin leading to a relative velocity between the model and the basin floor. It is found that for shallow water the results for the “tow” situation are 10% lower than for the “current” situation. Lastly, preliminary results for full scale are presented. At full scale the current coefficients are found to be lower than at model scale. However, more investigations should be carried out at full scale to be able to draw definite conclusions. From the results presented in this paper it is concluded that shallow water effects on current loads can be accurately obtained with CFD. Furthermore, blockage effects and the influence of “towing” versus a “current” situation have been quantified and a first study into scale effects has been presented.