Author

# G. Fekken

Bio: G. Fekken is an academic researcher from University of Groningen. The author has contributed to research in topics: Volume of fluid method & Free surface. The author has an hindex of 6, co-authored 8 publications receiving 667 citations.

##### Papers
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Journal ArticleDOI

TL;DR: In this paper, the authors considered some aspects of water impact and green water loading by numerically investigating a dambreak problem and water entry problems, based on the Navier-Stokes equations that describe the flow of a viscous fluid.

618 citations

01 Jan 1999
TL;DR: In this article, the problem of green water loading on the foredeck of a ship is discussed and a comparison is made with experimental results, and forces on different structures placed on the deck are compared and analyzed.
Abstract: Simulating viscous flows with a free surface causes special difficulties, since its position will change continuously. Therefore, besides solving the Navier-Stokes equations, the position of the free surface must be determined every time step. In the present method, the Navier-Stokes equations are solved on a three-dimensional Cartesian grid. A Volume-of-Fluid function is used for the position of the fluid. Since the method is able to handle arbitrary forms of the geometry, many types of industrial flow problems can be simulated. In this paper the problem of green water loading on the foredeck of a ship is discussed and a comparison is made with experimental results. Waterheights, pressures and water contours are produced and compared with model tests. Also forces on different structures placed on the deck are compared and analyzed.

51 citations

Proceedings ArticleDOI

01 Jan 2002
TL;DR: In this article, the simulation of green water on the foredeck of an FPSO is presented, where the waves are modeled as a dam of water around the deck which is suddenly released.
Abstract: Results of computer simulation of wave and green water loading on floating offshore structures are presented. The simulation program used is a CFD code which solves the Navier-Stokes equations that describe flow of incompressible viscous fluids. The Navier-Stokes equations are discretised using a Finite Volume method on a Cartesian grid with staggered variables. The free surface is displaced using a Volume Of Fluid based algorithm combined with a local height function. In this paper results of validation and sensitivity tests of simulation of green water on the foredeck of an FPSO are presented. Here, the waves are modeled as a dam of water around the deck which is suddenly released. Furthermore, wave loading from impact of regular waves on a SPAR platform is computed and compared with experimental results. The program is found to be robust and the computational results show good agreement with the experiments.Copyright © 2002 by ASME

20 citations

01 Jan 1999
TL;DR: In this paper, the numerics are based on finite-volume discretization on a three-dimensional Cartesian grid and the position of the fluid and thus the free surface is described by an Eulerian Volume-of-Fluid function F. Transportation of F is achieved using a local level-set function.
Abstract: Free-surface flows are difficult to simulate since the position of the free surface itself is part of the problem that needs to be solved. In the absence of gravity, simulation of free-surface flow is extra complicated because capillary effects dominate. In this case the shape of the interface drives the flow: the pressure at the free surface depends on the curvature of the surface. In our approach, the numerics is based on finite-volume discretization on a three-dimensional Cartesian grid. Special attention has been paid to the implementation of boundary conditions at non-gridaligned boundaries. The position of the fluid (and thus the free surface) is described by an Eulerian Volume-of-Fluid function F. Transportation of F is achieved using a local level-set function. Because the method is based on Cartesian grids, it is capable of simulating flows in arbitrary complex three-dimensional geometries. The method has already been used in a wide variety of (industrial) flow problems, such as green water loading on the foredeck of a ship and liquid sloshing aboard satellites.

17 citations

01 Jan 2001
TL;DR: In this paper, an extensive test series was carried out in which wedges were accelerated into the water with various velocities, and the results were presented of numerical simulations of a wedge that penetrates the water surface.
Abstract: In this paper results are presented of numerical simulations of a wedge that penetrates the water surface. An extensive test series was carried out in which wedges were accelerated into the water with various velocities. These tests were done to study bow-flare slamming and the wave run up around the bow of an FPSO. Some of these tests were selected for the numerical simulations. The simulations have been carried with a Navier-Stokes solver based on a modified Volume Of Fluid (VOF) method that keeps track of the position of the free surface. The measured position of the wedge during the tests and the geometry of the wedge was put into the program to enable a reproduction of the tests. The simulations show the typical behavior of the water after the wedge has penetrated the water surface. Measured and calculated pressures are compared and show a good similarity. Measured and calculated wave elevations in front of the wedge are less similar due to the violent water behavior. The method is a promising tool for the analysis of wave-impact problems on realistic ship hulls.

11 citations

##### Cited by
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Journal ArticleDOI

TL;DR: In this paper, the authors considered some aspects of water impact and green water loading by numerically investigating a dambreak problem and water entry problems, based on the Navier-Stokes equations that describe the flow of a viscous fluid.

618 citations

Journal ArticleDOI

TL;DR: In this article, a smoothed particle hydrodynamics model with numerical diffusive terms is used to analyze violent water flows and boundary conditions on solid surfaces of arbitrary shape are enforced with a new technique based on fixed ghost particles.

535 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed modified MPS methods for the prediction of wave impact pressure on a coastal structure by introducing new formulations for the pressure gradient and a new formulation of the source term of the Poisson Pressure Equation (PPE).

288 citations

Journal ArticleDOI

TL;DR: In this paper, the authors conduct experimental measurements on a dam break flow over a horizontal dry bed in order to provide a detailed insight, with emphasis on the pressure loads, into the dynamics of the dam break wave impacting a vertical wall downstream the dam.

236 citations

Journal ArticleDOI

13 Jun 2011-PLOS ONE
TL;DR: Both the achieved speed-ups and the quantitative agreement with experiments suggest that CUDA-based GPU programming can be used in SPH methods with efficiency and reliability.
Abstract: Smoothed Particle Hydrodynamics (SPH) is a numerical method commonly used in Computational Fluid Dynamics (CFD) to simulate complex free-surface flows. Simulations with this mesh-free particle method far exceed the capacity of a single processor. In this paper, as part of a dual-functioning code for either central processing units (CPUs) or Graphics Processor Units (GPUs), a parallelisation using GPUs is presented. The GPU parallelisation technique uses the Compute Unified Device Architecture (CUDA) of nVidia devices. Simulations with more than one million particles on a single GPU card exhibit speedups of up to two orders of magnitude over using a single-core CPU. It is demonstrated that the code achieves different speedups with different CUDA-enabled GPUs. The numerical behaviour of the SPH code is validated with a standard benchmark test case of dam break flow impacting on an obstacle where good agreement with the experimental results is observed. Both the achieved speed-ups and the quantitative agreement with experiments suggest that CUDA-based GPU programming can be used in SPH methods with efficiency and reliability.

219 citations