A Verification and Validation Study of CFD Simulations for the Flow Around A Tug

An important vessel for the operational process in a harbour is the tug, a vessel built for the specific purpose of quickly manoeuvring larger vessels in waterways. The key features of a tug are the towing and escorting performances under optimal conditions, which are often reached when sailing under drift at high Froude numbers. Potential users or buyers are comparing tugs on these key features. Thus, for tug designers it is of significant importance to correctly predict the performance of new designs, therewith enabling themselves to verify possible improvements. These predictions, based on lift and drag characteristics of the hull and appendages, are frequently performed using free running or captive model tests, which can be expensive, give no thorough insight in flow specifics and although large-scale models are used still suffer from scale effects. An alternative approach is the use of viscous flow computations, also called Computational Fluid Dynamics (CFD).
This present work will initially estimate the experimental uncertainties from captive model tests to obtain correct validation material. Thereafter a verification and validation exercise of free surface simulations with the KSKL turbulence model and a drift angle of 15 deg will be presented. These are followed by a turbulence sensitivity study of the KSKL, SST, EARSM and DDES turbulence model and finally simulations at other drift angles with the KSKL turbulence will be presented.