Viscous-inviscid coupling in free surface ship flows

1995 ◽  
Vol 21 (9) ◽  
pp. 699-722 ◽  
Author(s):  
E. Campana ◽  
A. Di Mascio ◽  
P. G. Esposito ◽  
F. Lalli
Keyword(s):  
Free Surface ◽  
Surface Ship ◽  
Ship Flows

Numerical Simulation of Surface Ship Motion in Regular Head Waves

2018 ◽  
Author(s):  
Lixiang Guo ◽  
Peng Wei ◽  
Zhiguo Zhang ◽  
Yue Sun ◽  
Jiawei Yu
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Pitch Angle ◽  
Degrees Of Freedom ◽  
Wave Length ◽  
Surface Ship ◽  
Dynamic Overset Grids ◽  
Head Waves ◽  
Heave Motion ◽  
Regular Head Waves

The motion of surface ship in wave environments is fully three-dimensional unsteady motion and includes complex coupling with hydrodynamic force and dynamic motion of the rigid body. This paper presents simulations of the KCS model with motions involve pitch and heave in regular head waves. Computations were performed with an in-house viscous CFD code to solve RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations and dynamic overset grids designed for ship hydrodynamics. RANS equations are solved by finite difference method and PISO arithmetic. Level-set method is used to simulate the free surface flow. The simulation geometry includes KCS hull and rudder under three conditions with three wave length and wave height combinations and two velocities (Fr = 0.26 and 0.33). Total resistance coefficient CT, heave motion z and pitch angle θ have been compared between CFD and EFD. Comparisons show that pitch and heave are much better predicted than the resistance. In the first section, simulations considered only 2 degrees of freedom (heave and pitch), for the second section, numerical simulation added the rolling motion to study the KCS in regular head waves. The second simulation cases were carried out with the same velocity and wave length and amplitude combination as the first cases. Comparisons of heave and pitch motion between 2DOF simulations and 3DOF simulations were presented in this paper. Results show the difference of heave motion z and pitch angle θ between the 2DOF and 3DOF-simulasions. In both cases the free surface were studied as an example of the flow generated by the ship pitching and heaving.

Modeling of Free Surface Effects Via Subgrid Scale Models

2004 ◽  
Author(s):  
Zeynep N. Cehreli ◽  
Ibrahim Yavuz ◽  
Ismail B. Celik
Keyword(s):  
Free Surface ◽  
Turbulent Flows ◽  
Mesh Size ◽  
Surface Effects ◽  
Subgrid Scale ◽  
Ship Wake ◽  
Eddy Simulation ◽  
Surface Ship ◽  
Scale Models ◽  
Large Eddy

In large eddy simulation, the key to the reliability of the solution with relatively large mesh size (this is unavoidable for high Re flows) is to develop effective and physically correct subgrid-scale (SGS) models. The behavior of various SGS models in large eddy simulations (LES) of free surface turbulent flows is investigated. The anisotropy of the turbulence observed near a free surface even a sub-grid scales can not be realized by a standard Smagorinsky model (SMG). The SMG model is improved with free surface modifications. This model is verified on an open channel flow benchmark and then applied to the simulation of a surface ship wake. The turbulence features are studied and compared with the results of a simulation without free surface effects. The modifications in the SGS model damps the vertical velocity fluctuations as desired. This study provides a better understanding of SGS models, when applied to the case of the wake of a turning surface ship.

Benchmarking of Computational Fluid Dynamics for Ship Flows: The Gothenburg 2000 Workshop

2003 ◽  
Vol 47 (01) ◽  
pp. 63-81 ◽  
Author(s):  
Lars Larsson ◽  
Frederick Stern ◽  
Volker Bertram
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Free Surface ◽  
Turbulence Modeling ◽  
Verification And Validation ◽  
Free Surface Waves ◽  
General Improvement ◽  
Hull Forms ◽  
First Time ◽  
Ship Flows

The Gothenburg 2000 was an international benchmark workshop for computational fluid dynamics applied to ship flows. Test cases were three modern hull forms. One case without a free surface focused on turbulence modeling, whereas wave prediction was of interest for the other two. Of the free-surface cases, one had an operating propeller. For the first time, verification and validation procedures were an integral part of such benchmark efforts in ship flows. The workshop showed that free-surface waves may now be well predicted also away from the hull. There is a general improvement in the computation of the stern flow thanks to better turbulence modeling, but there is still room for improvement. Full-scale viscous flows may be computed without numerical difficulties. Verification and validation procedures should be applied for uncertainty analysis, and there is a discussion of the uncertainty in the predicted integral quantities in the paper. Further detailed conclusions and recommendations are also given based on the comparison of extensive standardized plots of the comparative computations and evaluation of the integral quantities.

Application of two‐phase fluid approach for free‐surface ship flow simulation

2002 ◽  
Vol 25 (2) ◽  
pp. 179-188 ◽  
Author(s):  
Yen‐Jen Chen ◽  
Shiu‐Wu Chau ◽  
Jen‐Shiang Kouh
Keyword(s):  
Free Surface ◽  
Flow Simulation ◽  
Two Phase ◽  
Surface Ship ◽  
Phase Fluid ◽  
Ship Flow

scholarly journals Resistance Calculation and Motions Simulation for Free Surface Ship Based on CFD

2012 ◽  
Vol 31 ◽  
pp. 68-74 ◽  
Author(s):  
Aiguo Shia ◽  
Ming Wu ◽  
Bo Yang ◽  
Xiao Wang ◽  
Zuochao Wang
Keyword(s):  
Free Surface ◽  
Surface Ship

A Numerical Calculation of Hydrodynamic Forces on a Seagoing Ship by 3-D Source Technique With Forward Speed

2004 ◽  
Author(s):  
Yoshiyiki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Free Surface ◽  
Velocity Potential ◽  
Hydrodynamic Forces ◽  
The Body ◽  
Source Distribution ◽  
Accurate Estimation ◽  
Forward Speed ◽  
Surface Ship ◽  
Wave Patterns ◽  
Wigley Hull

In this paper, the hydrodynamic forces of a surface ship advancing in waves at constant forward speed are numerically calculated by using the 3-D source distribution techniques. The paper also deals with the numerical calculations of free surface flow around an advancing ship in calm water as well as in waves. The body boundary condition is linearised about the undisturbed position of the body and the free surface condition is linearised about the mean water surface. The potential is represented by a distribution of sources over the surface of the ship and its waterline. The problem is solved by the method of singularities distributed over the hull surface. Hess & Smith method is used to obtain the density of these singularities. The numerical solution of the surface ship case is approximately obtained by considering the hull as a position of plane polygonal elements, bearing a constant singularity distribution. The velocity potential of any particular point in the free surface around the moving hull is determined by using the 3-D Green function with forward speed which satisfies the boundary conditions for a pulsating source in the fluid. Contours of wave patterns around moving surface ships are calculated from the velocity potential. The numerical accuracy of the computer code is firstly checked by calculating the velocity potential of a translating, pulsating unit source with arbitrary frequency and forward speed. Free surface wave patterns generated by a Wigley hull advancing with steady forward speed are calculated by using this code. Some corresponding hydrodynamic coefficients of heave and pitch modes for the Wigley hull has been calculated. Exciting forces and motion amplitudes are also investigated. The numerical result of this code is validated by comparing the calculated results with the experimental ones and those calculated by other methods. From the comparison, the results predicted by the present calculations are found in fairly good agreement with the experiment. Finally, the effects of motion amplitude on the free surface elevation are analyzed. These will be helpful for the accurate estimation of sea keeping problems for a ship advancing in waves.

On the role of tin underlays for the prevention of thermal grooving in thin gold films

1986 ◽  
Vol 44 ◽  
pp. 732-733
Author(s):  
Jin Young Kim ◽  
R. E. Hummel ◽  
R. T. DeHoff
Keyword(s):  
Thin Film ◽  
Free Surface ◽  
Grain Boundary ◽  
Beneficial Effect ◽  
Failure Mechanism ◽  
Failure Mechanisms ◽  
Distinct Advantage ◽  
Gold Films ◽  
Gold Thin Film

Gold thin film metallizations in microelectronic circuits have a distinct advantage over those consisting of aluminum because they are less susceptible to electromigration. When electromigration is no longer the principal failure mechanism, other failure mechanisms caused by d.c. stressing might become important. In gold thin-film metallizations, grain boundary grooving is the principal failure mechanism.Previous studies have shown that grain boundary grooving in gold films can be prevented by an indium underlay between the substrate and gold. The beneficial effect of the In/Au composite film is mainly due to roughening of the surface of the gold films, redistribution of indium on the gold films and formation of In2O3 on the free surface and along the grain boundaries of the gold films during air annealing.

Sign in / Sign up

Export Citation Format

Share Document