Page 438 - Practical Design Ships and Floating Structures

Practical Design of Ships and Other Floating Structures 413
You-Sheng Wu, Wei-Cheng Cui and Guo-Jun Zhou (Eds)
0 2001 Elsevier Science Ltd. All rights reserved

SIMULATION OF VISCOUS FLOW OF MODERN SURFACE SHIPS
USING THE FINFLO RANS SOLVER

Ting-Qiu Li, Jerzy Matusiak

Ship Laboratory, Helsinki University of Technology
P.O.Box 4100(0takaari 4) FIN-02015 HUT, Finland

ABSTRACT

A FINFLO solver for simulation of a turbulent free-surface flow around a modem ship has been
developed through resolving the RANS equations with the artificial compressibility that incorporates a
treatment of the free-surface boundary conditions. Within a moving mesh system, a cell-centred finite-
volume multigrid scheme and two turbulence models, the Baldwin-Lomax model and the Chien's low
Reynolds number k-E model, are implemented. A non-linear free-surface boundary condition is
satisfied on the exact location of the surface. Test cases are three benchmarks recommended by the
ITTC, the DTMB 5415 model, the KCS model and the HTC model, including the tanker model from
the industry. The convergence performance and the effects of the grid size on the waves are
investigated. The computational results are validated and they are in good correlation with the EFD
data in terms of the free-surface waves and the total resistance coefficient.

KEYWORDS

Benchmark test Viscous free-surface flow, Ships with a transom, FINFLO RANS solver, a moving
~
mesh.

1 INTRODUCTION
A FINFLO-SHIP RANS version for simulation of a turbulent free-surface flow around a modem ship
in a numerical water tank has been developed by our CFD group at Helsinki University of Technology
(HUT). The capability of a numerical scheme provides the possibility for a ship design using the CFD
techniques. In our approach, the RANS equations with the artificial compressibility are resolved by a
cell-centred finite-volume multigrid scheme; an interface fitting method is implemented in order to
capture explicitly the interface between water and air, which results in an exactly non-linear kinematic
free-surface boundary condition is easy to be resolved. As a result, a high accuracy can be achieved for
the ship waves. whereas approximately dynamic free-surface boundary conditions are employed on
this surface. The steady state computations are performed on two selected transom types: a dry or a
partially wetted transom. Our approach is an uncoupled algorithm. This implies that all three
components of the velocities on the free surface are determined with the extrapolation.