A Verification and Validation Study Based on Resistance Submissions

Abstract

In Chap. 5 the database of ship total resistances submitted to the workshop is used to evaluate the error and uncertainty by means of a systematic verification and validation (V&V) study along with statistical investigations. Three representative methods are applied for verification: Grid Convergence Index, Factor of Safety and Least Squares Root. Validation of the results is carried out by the ASME V&V 20-2009 Standard. It is found that the iterative convergence is an important aspect in the numerical computation due to its contribution to the numerical uncertainty and its influence on the determination of discretization uncertainty. A limit for the iterative error is proposed. In the grid convergence study, unstructured grids are shown to more seldom achieve monotonic convergence than the structured grids. 2 to 10 million grid points and a grid refinement ratio 1.2 are most common among the research groups. In the study of structured grids using different verification methods, most solutions achieve monotonic convergence and are in the vicinity of the asymptotic range. Similar uncertainties are then predicted by the three methods. For cases further from the asymptotic range the methods predict quite different uncertainties. The scatter in solutions is an issue which is shown to significantly affect the determination of the grid convergence and the order of accuracy. In the validation study, the numerical error is mostly larger than the experimental error. Most solutions are estimated to have a smaller comparison error than validation error, implying that the modeling error is buried in the numerical and experimental noise.