Ship

Predicting ship hydrodynamics.

l Ship wave interaction.

l Ship resistance, propulsion, hull optimization.

l Maneuvering.

l Seakeeping.

l Autopilot, controllers, multi-ship interactions, etc.

l Simulation under the condition of mooring system.

l Hydrodynamic coefficients calculation serving for NDA (Nonlinear Dynamics Approaches) simulation.

l Others.

Case1: Free Surface Steady Flow around a Surface Combatant (3-D DTMB 5512 Ship with Deck, Fixed Sinkage and Trim)

Computation conditions

        Grid arrangement (for case of Fr=0.41: all hexahedral elements, for case of Fr=0.28 : mixed elements with some tetrahedral elements in bow region)

    Resistance coefficients for DTMB 5512 ship



                                              Top view of free surface for Fr=0.41                                                  Below view of free surface and streamline for Fr=0.41


                                                            Comparison of wave elevation with CFDSHIP-Iowa (Fr=0.41)

                                                                                           Wave profiles at the hull

                                                             Distribution of streamline near the ship hull and axial vorticity for Fr=0.41

   Distribution of level set function in the region of mixed elements ( Fr=0.28 )                                     Comparison of wave elevation with Experimental data (Fr=0.28)

                            u velocity                                                             v velocity                                                          w velocity

                                                                               velocity contour at the nominal wake plane (Fr=0.28)

Computation conditions

l Ship predicted motion of 2DOF: heave and pitch.

l Fr=0.41, Re= 1.35E+07 (ship length=5.72m).

l Dimensionless inputs: radius of gyration rg_y=0.25, weight coefficient =0.237,static area=0.074, gravity center (0.5054,0,-0.0097).

l Grid nodes: 615,000.

l Routine: 1) Restarting from the steady solution with fixed trim and sinkage of EFD of 5512 ship for saving computational time, 2) Artificial damp is used and coefficient=0.1.

                                     Heave and pitch history                                                                         Comparison of CFD values with Experimental data


                                       History of force coefficients (in ship system)                                                    History of moment coefficient (y axis)

Computation conditions

l Steady single water free surface flow, Reynolds number= 6.5E+6, Froude number=0.4.

l Five overset grids: ship hull, superstructure, bilge keel, skeg, and background grids.

l Overset grid solver produces static overset grid files and transfer to CFD.

　
                                     Frame of half ship grids                                                       Overset grids shown on ship hull

Top view Bottom view

Vortex and streamline

Computation conditions

l 5512 ship (1:46.6 of DTMB 5415 ), Fr=0.41,Re=7.1E+6.

l Incoming linear regular wave, wave length:1.5, wave slop: ak=0.025.

l Radius of gyration rg_2 =0.25, weight coefficient = 0.237, static area= 0.074, gravity center (0.5059,0, 0.00984).

l Pitch and heave motions are predicted, others are captive.

l Half ship grids are used due to symmetry to longitudinal section.

l Pitch and heave motions are predicted, others are captive.

l Test the computation in extremely coarse overset grids (close to limit condition) or coarse grids: Four coarse overset grids (only background grid is fixed, others follow ship motions).

l Verification and validation using three levels of coarse grids: 0.15, 0.25,0.40 million grids.