http://oa.upm.es/25973/1/INVE_MEM_2013_160560.pdf

Experimental investigation of dynamic pressure loads during dam break

The objectives of this work are to revisit the experimental measurements on dam break flow over a dry horizontal bed and to provide a detailed insight into the dynamics of the dam break wave impacting a vertical wall downstream the dam, with emphasis on the pressure loads. The measured data are statistically analyzed and critically discussed. As a result, an extensive set of data for validation of computational tools is provided.

https://pure.rug.nl/ws/files/31100157/WemmenhoveEtalCAF114_2015.pdf

Numerical simulation of hydrodynamic wave loading by a compressible two-phase flow method

Hydrodynamic wave loading on structures plays an important role in areas such as coastal protection, harbor design and offshore constructions (FPSO’s, mooring), and there is a need for its prediction up to a detailed level (max./min. pressures, duration of pressure peaks, shear stresses, etc.). In close cooperation with industry, long-year joint-industry projects are carried out to develop a numerical simulation method: the CFD method ComFLOW. The two major application areas are the prediction of extreme wave forces on offshore platforms and offloading vessels, and the prediction of impact forces on coastal protection structures. The paper will present a short overview of the method, some recent results and future plans.Copyright © 2011 by ASME

Extreme Wave Impact on Offshore Platforms and Coastal Constructions

In this paper, we present numerical modelling for the investigation of dynamic responses of a floating offshore wind turbine subject to focused waves. The modelling was carried out using a Computational Fluid Dynamics (CFD) tool. We started with the generation of a focused wave in a numerical wave tank based on a first-order irregular wave theory, then validated the developed numerical method for wave-structure interaction via a study of floating production storage and offloading (FPSO) to focused wave. Subsequently, we investigated the wave-/wind-structure interaction of a fixed semi-submersible platform, a floating semi-submersible platform and a parked National Renewable Energy Laboratory (NREL) 5 MW floating offshore wind turbine. To understand the nonlinear effect, which usually occurs under severe sea states, we carried out a systematic study of the motion responses, hydrodynamic and mooring tension loads of floating offshore wind turbine (FOWT) over a range of wave steepness, and compared the results obtained from two potential flow theory tools with each other, i.e., Electricite de France (EDF) in-house code and NREL Fatigue, Aerodynamics, Structures, and Turbulence (FAST). We found that the nonlinearity of the hydrodynamic loading and motion responses increase with wave steepness, revealed by higher-order frequency response, leading to the appearance of discrepancies among different tools.

Numerical Modelling of Dynamic Responses of a Floating Offshore Wind Turbine Subject to Focused Waves

Use of CFD tools for industrial offshore applications is a common practice nowadays. So is the need for validation of such tools against experimental results. This paper presents one of the CFD tools, ComFLOW, which solves Navier-Stokes equations and employs an improved Volume of Fluid (iVOF) method to find temporary location of fluid’s free surface. The code is used to simulate flow around a semi-submersible offshore platform due to an incoming regular wave. In particular, wave run-up on the semi’s columns and under-deck fluid impact phenomena are investigated on high-accuracy computational grids with number of cells being in range of 10 millions. Results of numerical simulations are compared with experimental data and focus is on local fluid flow details in immediate vicinity of the platform. Wave run-up on the platform’s columns and fluid pressures at various locations, including under-deck impact, are reported and verified against the experiment for a range of incoming wave heights.Copyright © 2009 by ASME

/pdf/cfd-simulation-of-wave-run-up-on-a-semi-submersible-and-2py5g9xotf.pdf

CFD Simulation of Wave Run-Up on a Semi-Submersible and Comparison With Experiment

Simulation of liquid dynamics in an LNG tank is studied numerically. The applied CFD code solves Navier-Stokes equations and uses an improved Volume of Fluid (iVOF) method to track movement of fluid’s free surface. Relative advantages of using two different fluid models, single-phase (liquid+void) and two-phase (liquid+compressible gas) are discussed, the latter model being capable of simulating bubbles and gas entrapped in liquid. Furthermore, the 1st and 2nd order upwind differencing schemes are used with both physical models leading to a total of four possible approaches to solve the problem. Numerical results are verified against experimental data from large scale (1:10) sloshing experiments of 2D section of an LNG carrier. The CFD vs. experiment comparison is shown for tank filling rates of practical interest, ranging from 10% to 95%, and includes both fluid height and fluid pressure exerted on tank walls. A visual comparison in form of computer animation frames, synchronised with camera-made movies taken during the experiments is included as well. Finally, an exhaustive computational grid convergence study is presented for lower filling rates of the tank.Copyright © 2009 by ASME

Numerical Simulation of Sloshing in a Tank, CFD Calculations Against Model Tests

The dambreak experiment is a widely used test case for validation of CFD methods and is applied here to examine sloshing physics. Wave profiles and impact pressure profiles for the dambreak experiment are to some extent representative of those in a 2D sloshing tank. Available data from experiments show a high pressure peak for the first fluid impact. Numerical investigation of liquid dynamics and the resulting impact on the wall of the experimental chamber is presented. Interaction between fluid and structure is investigated by studying several cases with either rigid or flexible walls. Two numerical approaches are considered and their results are compared with experimental data. The first, CFD code ComFLOW, solves Navier-Stokes equations by the Finite Volume Method and uses an improved Volume of Fluid (iVOF) method to track free surface movement. Walls of the chamber are modelled as rigid. One-phase and two-phase fluid models are applied, the latter being capable of simulating bubbles and gas entrapped in liquid. The second approach employs Finite Elements and a well-known commercial FEM code, LS-DYNA, is used. Fluid flow modelling options include an Arbitrary Lagrangian-Eulerian scheme, which is applied here to compute liquid dynamics and impact loads on tank walls. Cases with rigid and flexible walls are examined to investigate fluid-structure interaction.

Comparison of CFD Calculations And Experiment For the Dambreak Experiment With One Flexible Wall

The paper presents an industrial application of CFD and non-linear structural response codes in offshore technology. A Wave-In-Deck load due to an extreme wave, acting on a jacket platform, is studied numerically. Particular attention is given to details of local flow and local non-linear dynamical response of the structure. A very detailed FEM model of the platform deck structure, composed of shell elements, is embedded into a non body-conforming CFD grid of computational cells. The applied CFD code is a Navier-Stokes equation solver with an improved Volume of Fluid (iVOF) method employed to displace and re-construct fluid’s free surface and uses a simple, Cartesian grid. The two computational grids, FEM and CFD, are independent. The challenge of a direct mapping of CFD-derived fluid pressures onto structural FEM shell elements is addressed. Then the non-linear dynamical response of the structure is found in time domain. The employed CFD code is ComFLOW while the FEM part is handled by the well-known commercial program LS-DYNA. The composed approach utilizes both robustness of VOF-based methods in tracking of the fluid’s free surface and reliability of FEM structural codes such as LS-DYNA.Copyright © 2009 by ASME

/pdf/wave-in-deck-load-on-a-jacket-platform-cfd-derived-pressures-4oohppnat5.pdf

Wave-In-Deck Load on a Jacket Platform, CFD-Derived Pressures and Non-Linear Structural Response

Numerical study of liquid dynamics in an LNG tank is presented. The available data from large scale (1:10) sloshing experiments of 2D section of an LNG carrier reveal large scatter in recorded values of peak pressures. The experimental data is analysed from statistical point of view in order to obtain distributions of the pressure peaks. Then the entire experimental data record is reproduced numerically by CFD simulations and it is shown that pressure peaks obtained numerically display scatter of values as well. A statistical description of the numerically obtained record is provided and compared with description derived from the experimental data. The applied CFD code ComFLOW solves Navier-Stokes equations and uses an improved Volume of Fluid (iVOF) method to track movement of fluid’s free surface. Two different fluid models, single-phase (liquid+void) and two-phase (liquid+compressible gas) can be applied, the latter model being capable of simulating bubbles and gas entrapped in liquid. For low tank filling rate discussed in the paper (10%) the single-phase approach is sufficient. Comparison of statistical properties of experimental and numerical records is offered.Copyright © 2010 by ASME

/pdf/numerical-investigation-of-sloshing-in-a-tank-statistical-r60die3f6c.pdf

Marc Lefranc

Papers

CFD Simulation of Wave Run-Up on a Semi-Submersible and Comparison With Experiment

Numerical Simulation of Sloshing in a Tank, CFD Calculations Against Model Tests

Comparison of CFD Calculations And Experiment For the Dambreak Experiment With One Flexible Wall

Wave-In-Deck Load on a Jacket Platform, CFD-Derived Pressures and Non-Linear Structural Response

Numerical investigation of sloshing in a tank, statistical description of experiments and cfd calculations