INTERNATIONAL COLLABORATION ON BENCHMARK CFD VALIDATION DATA FOR SURFACE COMBATANT DTMB MODEL 5415

Results are presented from overlapping towing tank tests between three institutes for resistance, sinkage and trim, wave profiles and elevations, and nominal wake using the same model geometry and conditions, including rigorous application of standard uncertainty assessment procedures. Two of the institutes used 5.7 m models whereas the third institute used a smaller 3 m model. Comparison variables were defined for data-reduction equations and data differences and data-difference uncertainties. Detailed descriptions were provided of facilities, measurement systems, data acquisition and reduction procedures, and uncertainty assessment. Results were discussed with regard to levels and causes of data differences and data-difference uncertainties and to estimate facility/model geometry and scale effect biases. For same size 5.7 m models, data differences were in general oscillatory, and in many cases, larger in magnitude than data-difference uncertainties, which indicates unaccounted for bias and precision limits and that current individual facility uncertainty estimates are often too optimistic. Scale effects for the 3 m model are only evident for resistance and trim tests at high Fr. Facility/model geometry and scale effect bias are estimated based on comparisons. Uncertainty estimates including such biases may provide better estimates, especially for use in computational fluid dynamics (CFD) validation, which is the recommendation of the present study along with efforts towards improvement of individual institute uncertainty estimates. Use of standard models and current ITTC efforts in providing standard quality manual procedures for towing tank tests and uncertainty estimates will also be helpful in this regard.