Investigation of the turning performance of a surface combatant with urans

The prediction of ship-maneuvering performance have been challenging topics in ship hydrodynamics research due to its non-linear and highly complex nature. The turning maneuvering performance of a surface combatant is investigated with URANS method in this study. Numerical simulations of static PMM (Planar Motion Mechanism) tests are performed toward this goal by using a commercial RANSE solver software Star CCM+ in an unsteady manner. The fluid flow is considered as 3-dimensional, incompressible and fully turbulent. The free surface effect has been taken into account by including volume of fluid (VOF) method. Grid independence study is performed for 4 different grid quality. The effect of turbulence model is investigated by using two-equation models. The URANS and Eulerian approaches are investigated for several cases. The computational results, e.g., forces, moments, are used to determine the hydrodynamic derivatives according to Abkowitz's mathematical model. The acceleration and angular velocity derivatives are used as described in literature. The rudder terms are calculated from the results of "drift and rudder" simulations. The prefered ship model is DTMB 5512, which is a 1/46.6 scale of US Navy DDG51 frigate, with L=3.048 m and geosim of DTMB 5415. Numerical analyses are performed in a 19.507m x 14.630m x 6.401m virtual towing tank for fixed condition. Hull is identified as a non-slip wall in order to dictate kinematic boundary condition. Front, top and bottom faces of the computational domain are defined as velocity inlets. Side faces are assigned as symmetry-planes and the back face is defined as pressure outlet. VOF wave is defined at draft of the ship as calm water. Computational results are compared with the available experimental data. Turbulent kinetic energy and vorticity magnitude are observed on the plane sections normal to the x-direction for several cases. The results for two-equation turbulence models are examined and the suitable turbulence model for the presented study is selected. Wave profiles along the hull are plotted and compared with the EFD validation data. The viscous and inviscid flow results are compared with each other for several cases. Hydrodynamic derivatives are compared with the EFD results and empirical formulas and then are used as inputs to DYNEQNOMS (Dynamic Equations of Motion Solver), which is a custom developed computer program within the scope of this study to simulate ship turning maneuver. The turning maneuver performance parameters are compared with the literature.