An investigation into the scale effect on the total resistance of a container ship in shallow water

U ovom radu provedene su numeričke simulacije pokusa otpora modela broda i broda u naravi u neograničenoj i plitkoj vodi za kontejnerski brod DTC. Numeričke simulacije provedene su primjenom komercijalnog programskog paketa za računalnu dinamiku fluida (RDF) STAR–CCM+. Primijenjen je matematički model nestacionarnog trodimenzijskog viskoznog strujanja fluida sa slobodnom površinom na temelju Reynoldsovih osrednjenih Navier – Stokesovih jednadžbi (eng. Reynolds Averaged Navier – Stokes, RANS). Korišten je k – ω SST model turbulencije i metoda udjela fluida u volumenu (eng. Volume of Fluid, VOF) za praćenje i određivanje položaja slobodne površine. Simulacije su provedene za dva Froudeova broja te je proveden postupak verifikacije s ciljem određivanja numeričke nesigurnosti ukupnog otpora, urona/izrona te trima modela broda i broda u naravi za jedan Froudeov broj primjenom različite gustoće mreže i vremenskog koraka za slučaj neograničene i plitke vode. Dobiveni numerički rezultati za model broda u plitkoj vodi uspoređeni su s dostupnim eksperimentalnim podacima, dok su za brod u naravi uspoređeni s ekstrapoliranim rezultatima eksperimentalnih ispitivanja. Također, dan je detaljan prikaz strujanja oko trupa modela broda i broda u naravi u plitkoj vodi te je dana usporedba povećanja ukupnog otpora u plitkoj vodi u odnosu na neograničenu dubinu za model broda i brod u naravi.In this study, numerical simulations of resistance test for DTC container ship at model and full scale in unlimited and shallow water are carried out. Numerical simulations are performed within a commercial software package for Computational Fluid Dynamics (CFD) STAR – CCM+. A mathematical model of unsteady three – dimensional viscous flow with a free surface based on Reynolds averaged Navier – Stokes (RANS) equations is applied. The k – ω SST turbulence model is used, and the Volume of Fluid (VOF) method is applied for tracking and locating the free surface. The numerical simulations are carried out for two Froude numbers. The verification study is performed to assess the numerical uncertainty of the total resistance, sinkage, and trim for the ship model and full – scale ship at one Froude number using different grid densities and time steps in unlimited and shallow water. The obtained numerical results for the ship model in shallow water are compared with the experimentally obtained data, while for the full – scale ship are compared with the extrapolated results of the experimental tests. Also, a detailed description of the flow around the ship model and full – scale ship in shallow water is given. A comparison of the increase in total resistance in shallow water and unlimited depth for the ship model and full – scale ship is provided as well