Dynamic overset grids in OpenFOAM with application to KCS self-propulsion and maneuvering

An implementation of the dynamic overset grid technique into naoe-FOAM-SJTU solver developed by using the open source code OpenFOAM is presented. OpenFOAM is attractive for ship hydrodynamics applications because of its high quality free surface solver and other capabilities, but it lacks the ability to perform large-amplitude motions needed for maneuvering and seakeeping problems. The implementation relies on the code Suggar to compute the domain connectivity information (DCI) dynamically at run time. Several Suggar groups can be used in multiple lagged execution mode, allowing simultaneous evaluation of several DCI sets to reduce execution time and optimize the exchange of data between OpenFOAM and Suggar processors. A towed condition of the KRISO Container Ship (KCS) are used for static overset tests, while open-water curves of the KP505 propeller and self-propulsion and zig-zag maneuvers of the KCS model are exercised to validate the dynamic implementation. For self-propulsion the ship model is fitted with the KP505 propeller, achieving self-propulsion at Fr=0.26. All self-propulsion factors are obtained using CFD results only, including those from open-water curves, towed and self-propulsion conditions. Computational results compare well with experimental data of resistance, free-surface elevation, wake flow and self-propulsion factors. Free maneuvering simulations of the HSVA KCS model appended with the HSVA propeller and a semi-balanced horn rudder are performed at constant self-propulsion propeller rotational speed. Results for a standard 10/10 zig-zag maneuver and a modified 15/1 zig-zag maneuver show good agreement with experimental data, even though relatively coarse grids are used. Grid convergence studies are performed for the open-water propeller test and bare hull KCS model to further validate the implementation of the overset grid approach.