Abstract
This study develops and implements a two-layer, two-point wall-function model in the general-purpose URANS/DES solver CFDSHIP-IOWA-V.4 to routinely simulate model-and full-scale ship flows for resistance, propulsion, seakeeping, and maneuvering. The wall-function is validated for smooth flat-plate flows for high Reynolds numbers, and applied to study high speed transom ship flows, Athena R/V. Resistance predictions for Athena barehull with skeg at model-scale compare well with the near-wall turbulence model results and EFD data. For full-scale simulations frictional resistance predictions are in good agreement with the IITC line. No significant Reynolds number effect is found for free surface wave elevation and sinkage and trim (smooth wall). Full-scale boundary layer is thinner than that of the model-scale. Rough wall simulations show higher frictional and total resistances and relative large and unexpected changes are observed for sinkage and trim, which may be due to the coarse grid used and needs to be confirmed by further study. Resistance and powering computations are performed at full-scale for self-propelled fully appended Athena free to sink and trim with smooth-and rough-walls, and results are compared with full-scale data extrapolated from model scale measurements using ITTC ship-model correlation line including a correlation allowance. Rough wall conditions predict higher frictional and total resistances leading to better Froude number and resistance without significant effects on sinkage and trim. Sinkage and trim are not significantly affected by Reynolds number. Full-scale computations are performed for the towed fully appended Athena free to sink and trim and the boundary layer and wake profiles are compared with full-scale EFD data. Rough-wall results are found to be in better agreement with the EFD data than the smooth-wall results. Transom flow instability is studied for the fully appended Athena free to sink and trim at full-scale using DES with the wall-function. Karman-like vortex shedding and associated instabilities are analyzed and compared with the previous URANS/DES for the Athena barehull at model-scale. Seakeeping capability of the wall-function is also demonstrated at both model-and full-scale. Finally, limitations of the current wall-function approach and future work are discussed.