Computation Of Ship Manoeuvring Related Viscous Flow And Hydrodynamic Forces

Numerical prediction of ship hydrodynamic performance at design stage using computational fluid dynamics (CFD) technique is a most important and challenging subject in the field of ship hydrodynamics. With the rapid development of computational methods and computer technology, CFD is becoming a practical tool in ship design. In this respect, it tends to be an alternative of towing tank tests. The solution of 3D viscous flows around a ship in steady straightforward courses is capable of capturing more nearfield flow features than model tests and predicting viscous resistance with high accuracy, whilst for viscous flows around a ship in maneuvering motions such predictions are only in general good.A multi-block incompressible viscous flow solver has been developed that can be applied to simulation of a variety of ship maneuvering related flows and calculation of hydrodynamic forces. Validation and verification of the solution procedure are carried out on several model problems with good agreement to experimental and numerical results.The present block-structured viscous flow solver is based on solving the Reynolds-averaged Navier-Stokes (RANS) equations with a second-order cell-centered finite volume method (FVM) on non-staggered grids. The standard k-ε turbulence model with wall function is incorporated into the RANS solver for turbulent flow modeling. Several procedures are proposed for satisfying boundary conditions. The convection term is approximated by hybrid upwind/central differencing scheme, the diffusion and source terms are approximated using central differencing scheme with locally approximated implicit terms taken to strengthen the main-diagonal of the final coefficient matrix. The SIMPLE method is used for the pressure coupling, and the Strong Implicit Procedure (SIP) is adopted for solution of the discretized equations. The solution algorithm employs under-relaxation in eachiterative step for numerical stability and the multigrid method for better convergence rate. The solver is coded using the C++ programming language and named VSMAN.The present flow solver is demonstrated for block-structured meshes with calculations of the viscous flows around a rudder with NACA0015 foil profile at a range of attack angles. The effect of Reynolds number on rudder hydrodynamic performance is also analyzed. Up to the stall angle the computed lift and drag agree well with measurements and other author's calculations, whereas stall angle, lift and drag beyond the stall angle are slightly under-predicted.The solver is used to investigate laminar and turbulent separated flows around a 6:1 prolate spheroid at high incidence angles and their effects on hydrodynamic forces. The second separation flows are successfully identified in both laminar and turbulent flow simulations. The computations are shown to agree well with available experimental and numerical data and the physics of 3D large-scale flow separations and vortex shedding are confirmed.The simulation of the flow around a maneuvering Wigley hull is a demonstration of capability for calculations of sway forces and yaw moments acting on a hull moving obliquely at a large range of yaw angles. The focus of study is large-scale cross-section separation flows, bilge-vortex development along the hull in the longitudinal direction and their effects on hydrodynamic forces. The results are compared with the available experimental and numerical data which has shown good agreement.A visualization program named SCFDVS is developed specifically for plotting 2D/3D geometries and numerical grids, 2D/3D scalar and vector fields in ship CFD simulations. The visualization system is quite efficient and user-friendly, and is already used for better presentation of numerical results.The work covered in this thesis is hoped to shorten the gaps to the world advanced level in prediction of hydrodynamic forces on maneuvering ships. Due to the complexity of ship maneuvering viscous flows, the computational methods for such flows are nevertheless in its infant, t...