Numerical study on a KVLCC2 model advancing in shallow water (original) (raw)
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Numerical Analysis of Added Resistance and Vertical Ship Motions in Waves for KVLCC2
Journal of the Korean Society of Marine Environment and Safety, 2016
The present study provides numerical simulations to predict the added resistance and ship motion of the KVLCC2 in regular waves using the unsteady Reynolds-Averaged Navier-Stokes (URANS) and 3-D potential methods. This numerical analysis is focused on added resistance and vertical ship motions (heave and pitch) under a wide range of wave conditions at three ship speeds (design, operating and zero speeds). Firstly, the characteristics of the CFD and 3-D potential flow methods are presented to predict added resistance and ship motions in regular waves taking into account various wave conditions at design speed to provide a validation study as well as at operating and zero speeds. Secondly, analyses of added resistance and ship motion with unsteady wave patterns and time history results as simulated by CFD were performed at each ship speed. Systematic validation and verifications of the numerical computations in this study were made against available Experimental Fluid Dynamics (EFD) data including grid convergence tests to demonstrate that reliable numerical results were obtained for the prediction of added resistance and ship motion in waves. Relationships between added resistance, vertical motion and changes in ship speeds were also found.
URANSE simulation for the Seakeeping of the KVLCC2 Ship Model in Short and Long Regular Head Waves
IOP Conference Series: Materials Science and Engineering, 2019
In the present study, the vertical motions and the added resistance in waves of the KVLCC2 ship model are predicted numerically in regular head wave, for a single wave height and different wave lengths, including long and short waves. The numerical simulation is performed by making use of the ISIS-CFD solver of the commercial software FineTM/Marine provided by NUMECA, where the discretization in space is based on finite volume method using unstructured grid. The unsteady RANSE are numerically solved, while the turbulence is modelled by making use of the k-ω SST model. The free-surface is captured through an air-water interface based on the Volume of Fluid method. For validation purposes, the computed solutions are compared with the available tank test data existing in the public domain. A systematic grid convergence study based on Richardson Extrapolation method is performed for a single wave case on three different grid resolutions, as an attempt of predicting the uncertainties in ...
Theoretical and experimental investigations of wave field around vessel in shallow water
Herald of the Odessa National Maritime University, 2020
Un-running vessel at the shallow-water road anchorage is under exposure to waves that come at arbitrary angle from the high sea. 3D waves from deep-sea area become practically 2D when entering shallow water. While mean periods are kept, waves become shorter and their crests become higher and sharpener than for deep-water ones. As a result of diffraction of waves that come from the deep-water sea at the vessel, a transformation zone appears where waves become 3D again. Dimensions of the waves’ transformation zone, character and height of waves in this zone specify safety of auxiliary crafts, e.g. tugboats, bunker vessels, pilot and road crafts, oil garbage collectors and boom crafts. In the complex 3D waves the trajectory of auxiliary vessel’s movement has to be safe, vessel’s motions have to be moderate. Besides waves’ height is one of the parameters that are used for forecast of movement of spilled oil. Last years the biggest part examination of waves’ problems was devoted to estim...
A WAVE MODEL FOR SIMULATING VESSEL EFFECTING SHALLOW WATER WAVES IN A MARITIME SIMULATOR (Paper)
In modeling of the ocean wave effects in a Maritime Simulator, the area of shallow water waves has taken precedence in recent times. Our study experiments the possibilities of overcoming the barrier of high computation shallow water wave models that cannot be used for real time applications. Quoting from literature there exists three main approaches to model ocean waves: 1) Geometrical Description Models, 2) Spectral Models & 3) Physical based numerical models. The interest of this research is towards models that are able to achieve high accuracy in terms of the wave properties; thus allowing to accurately depict wave conditions. It is the approach of numerically solved physical based models (from those mentioned above) that can solve for wave parameters with high accuracy. The challenge imposed by such accurate models is the computation complexity that results in long processing time. Hence, they are not the most suitable choice for real-time simulators. Our study experiments the possibility of a solution to this problem by restricting the simulation area to only that which has an impact on the vessel and by introducing cell reductions. The results obtained within the duration of this study, reveal that maintaining an optimal accuracy with such mesh-restrictions is not feasible and further efforts needs to be put in terms of parallel/gpu processing, profiling & etc.
International Journal of Naval Architecture and Ocean Engineering, 2018
In this study, numerical simulations for the prediction of added resistance for KVLCC2 with varying wave steepness are performed using a Computational Fluid Dynamics (CFD) method and a 3-D linear potential method, and then the non-linearities of added resistance and ship motions are investigated in regular short and long waves. Firstly, grid convergence tests in short and long waves are carried out to establish an optimal mesh system for CFD simulations. Secondly, numerical simulations are performed to predict ship added resistance and vertical motion responses in short and long waves and the results are verified using the available experimental data. Finally, the non-linearities of added resistance and ship motions with unsteady wave patterns in the time domain are investigated with the increase in wave steepness in both short and long waves. The present systematic study demonstrates that the numerical results have a reasonable agreement with the experimental data and emphasizes the non-linearity in the prediction of the added resistance and the ship motions with the increasing wave steepness in short and long waves.
Third order contribution to the wave-making resistance of a ship at finite depth of water
Ocean Engineering, 2007
This paper presents a potential based boundary element method for solving a nonlinear free surface flow problem for a ship moving with a uniform speed in finite depth of water. The free surface boundary condition is linearized by the systematic method of perturbation in terms of a small parameter up to third order. The surfaces are discretized into flat quadrilateral elements and the influence coefficients are calculated by Morino's analytical formula. Dawson's upstream finite difference operator is used in order to satisfy the radiation condition. The second order solution gives better result than the first or third order solution. So the present method with the second order solution can be adopted as a powerful tool for the hydrodynamic analysis of the thin ship in finite depth of water.
Numerical study of viscous wave-making resistance of ship navigation in still water
Journal of Marine Science and Application, 2014
The prediction of a ship's resistance especially the viscous wave-making resistance is an important issue in CFD applications. In this paper, the resistances of six ships from hull 1 to hull 6 with different hull forms advancing in still water are numerically studied using the solver naoe-FOAM-SJTU, which was developed based on the open source code package OpenFOAM. Different components of the resistances are computed and compared while considering two speed conditions (12 kn and 16 kn). The resistance of hull 3 is the smallest while that of hull 5 is the largest at the same speed. The results show hull 3 is a good reference for the design of similar ships, which can provide some valuable guidelines for hull form optimization.
2015
Steady three-dimensional and two free surface waves generated by moving bodies are presented, the flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. The results of several simulations are reported. The first study was performed for NACA0012 of hydrofoil with different meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second simulation a mathematically defined Wigley hull form is used to investigate the application of a commercial CFD code in prediction of the total resistance and its components from tangential and normal forces on the hull wetted surface. The computed resistance and wave profiles are used to estimate the coefficient of the total resistance for Wigley hull advancing in calm water under steady conditions. The commercial CFD software FLUENT version 12 is used for the com...
Applied Ocean Research, 2019
Analysis of a craft with two degrees of freedom (2DOF) consumes time more than simulation of a craft with a fixed trim condition; therefore in most of the previous researches fixed trim condition is taken into account to analyze the flow field around a craft in shallow water and head sea wave conditions. In this paper numerical simulation of Reynolds Average Naiver Stokes (RANS) equations are used to analyze the motion of DTMB 62 model 4667-1 planing vessel in calm water and head sea waves in both deep and shallow water with two degrees of freedom (heave and pitch). For this purpose, a finite volume ANSYS-FLUENT code is used to solve the Navier-Stokes equations for the simulation of the flow field around the vessel. In addition, an explicit VOF scheme and SST k-ω model is used with dynamic mesh scheme to capture the interface of a two-phase flow and to model the turbulence respectively in the 2DOF model. Regarding the results, reducing the wavelength and also the depth of the water can increase the drag force. Also comparing the results of a fixed trim vessel with the results of a free to sink and trim one in calm water shows a difference of approximately 50% in the drag force in shallow water.