CFD Simulations of a Semi-Submersible With Absorbing Boundary Conditions

Wellens, Peter; Luppes, Roel; Veldman, Arthur; Borsboom, Mart

doi:10.1115/omae2009-79342

Cited by 10 publications

(7 citation statements)

References 17 publications

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“…Linear potential theory for waves was used to displace this information to the inflow boundary at x = -3m. At the inflow end of the domain, a Generating Absorbing Boundary Condition (GABC) is specified, see Wellens et al (2009). The same boundary condition was used at the outflow end of the domain, but no waves enter the domain at the outflow boundary.…”

Section: Setup Of the Simulationsmentioning

confidence: 99%

“…An alternative for dissipation zones is to develop accurate local absorbing boundary conditions (ABCs) for waves. An ABC for long-crested, dispersive waves with normal incidence to the boundary is presented in Wellens et al (2009). This ABC, however, gives too much reflection as the wave direction with respect to the outward normal to the boundary becomes larger than approximately 30°.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Wave Motion Near a Breakwater Roundhead

Honda¹,

Wellens²,

Gent³

2012

Int. Conf. Coastal. Eng.

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COMFLOW is a general 3D free-surface flow solver. The numerical method is based on the Navier-Stokes equations in a porous medium, with additional force terms to represent the (turbulent) interaction of the flow with the medium. The free surface is displaced by means of the Volume-Of-Fluid method. The main objective in this paper is to validate the permeable flow model in 3D. Tailor-made physical model tests were performed for this purpose. In the experiment surface elevations are measured inside and around a permeable structure with 18 wave gauges in total. The measurements are represented well by the simulation results.

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Section: Setup Of the Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Wave Motion Near a Breakwater Roundhead

Honda¹,

Wellens²,

Gent³

2012

Int. Conf. Coastal. Eng.

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“…* When the total wave signal at the inflow boundary is decomposed as Φ = Φ in + Φ out , then it is straightforward to substitute this relation in (16) to achieve a boundary condition which is fully transparent allowing waves to penetrate into the domain and also to move out of the domain. * Comparing the reflection coefficients given in (11), (12) and (17), the latter provides more control over the reflection property of the boundary condition. For appropriately prespecified values of the parameters in (17), the spurious reflection from the boundary will become small for a region in the vicinity of a kh value.…”

Section: Mathematical Formulationmentioning

confidence: 99%

Towards a General-Purpose Open Boundary Condition for Wave Simulations

Düz

Huijsmans

Wellens

et al. 2011

Volume 7: CFD and VIV; Offshore Geotechnics

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For the design of FPSO’s in harsh environments an accurate assessment of the ability of the platform to survive in extreme sea conditions is of prime importance. Next to scaled model tests on the FPSO in waves also CFD capabilities are at the disposal of the designer. However even with the fastest computers available it is still a challenge to use CFD in the design stage because of the large computational resources they require. In that respect to use a small computational domain will improve the turn around time of the computations, however at the expense of various numerical artifacts, like reflection on artificial boundaries in the computational domain. In order to mitigate the reflection properties new absorbing boundary conditions have been developed. The work in this paper is constructed on the previous study about the generating and absorbing boundary condition (GABC) in the ComFLOW project. We present a method to apply the GABC on all the boundaries in a three dimensional domain. The implementation of the GABC in ComFLOW is explained in detail.

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“…Simultaneously, outgoing waves should be able to leave the domain through all numerical boundaries without spurious reflections. The Generating and Absorbing Boundary Condition (Wellens et al (2009)), abbreviated as GABC, in ComFLOW is a boundary condition that ensures wave generation and wave absorption at the same time. The Sommerfeld radiation boundary condition for a velocity potential…”

Section: Numerical Modelmentioning

confidence: 99%

Volume-of-Fluid Model Comflow Simulations of Wave Impacts on a Dike

Wenneker

Wellens

Gervelas

2011

Int. Conf. Coastal. Eng.

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ComFLOW is a 3D Volume-of-Fluid (VOF) model to solve the incompressible Navier-Stokes equations including free surface, or to solve the Navier-Stokes equations for two-phase flow problems (two-phase flow: both an incompressible viscous fluid (e.g., water) and a compressible viscous fluid (e.g., air) are present). The problem statement of the present study reads: ‘Is ComFLOW capable of accurate prediction of wave impacts on (impermeable) coastal structures such as dikes? And, if so, what are the preferred model settings and associated computing times?’. In this paper, ComFLOW is validated for this purpose by comparison against pressure data as measured in the Delta flume by pressure sensors at dikes. We have selected three different experiments, with typical dike geometries (slope 1:3.5, with and without berm) at which more than 20 pressure sensors were installed. The results can be summarized as follows. The pressure measurements are reproduced well in the simulations. A grid with about 170 grid cells per wave length in the horizontal, and between 4 and 6 grid cells per wave height in the vertical, proves to be sufficiently fine. At such a grid resolution and with about 450 by 35 grid cells in the computational domain, a typical CPU time is 35 minutes for simulations with a model time of 10 wave periods. For the present application, it is preferable to use the one-phase flow model rather than the two-phase flow model, since the former gives better results in the lower located pressure sensors and consumes less CPU time.

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CFD Simulations of a Semi-Submersible With Absorbing Boundary Conditions

Cited by 10 publications

References 17 publications

Wave Motion Near a Breakwater Roundhead

Wave Motion Near a Breakwater Roundhead

Towards a General-Purpose Open Boundary Condition for Wave Simulations

Volume-of-Fluid Model Comflow Simulations of Wave Impacts on a Dike

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