Floating Object Stability Modeling with OpenFOAM - Tutorial

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Modeling the interaction in between objects and fluid comes with certain complexities due to the multi-state problem configuration (liquid-solid) and the dynamic mesh required for the simulation. Fortunately, those complexities can be handled with OpenFOAM, its solvers and the implementation of dynamic mesh.

Certainly, the adoption of a dynamic mesh involves new parameters to conceptualize and perform a quality control on the simulation. The floating object requires parameters for geometry, density, center of inertia, degrees of freedom, restraints and so on. On the model file system new folders and files appear as pointDisplacement, motionScale, dynamicCode and blockMeshDict. The learning process of this type of simulations requires to read much documentation, get familiar with the parameters and practice on test cases and tutorials.

For a numerical modeler, the concept of mesh deformation is quite nirvana on the model conceptualization since nature can be modeled no only on steady/transient conditions with a constant geometry, but also with changes in the model geometry with time. Model is a tool to understand nature and get solutions from it; as long as more tools are available, better the chances to address a problem/phenomena with higher accuracy.

 Model mesh at simulation start

Model mesh at simulation start

 Model mesh after 1.2 seconds

Model mesh after 1.2 seconds

This tutorial is about a floating object stability simulation from a water surface oscillation (wave). The model was done with the interFoam solver that is a solver for two incompressible fluids, on isotermic conditions using a volume of control (VOF) phase-fraction interface approach. Turbulence was conceptualized on the model with the kEpsilon turbulence model. Simulation was done for 4 seconds with outputs every 0.05 seconds and runs in almost 5 minutes on OpenFOAM for Windows, better computation times are expected when run on Linux with paralleling computing.

  

Tutorial 

The tutorial is divided in two parts, the first is for model construction and the second for the result analysis.

Part one - model construction

Part two - output analysis

 

Input files

Input files for this tutorial can be found on this link.

Saul Montoya

Saul Montoya es Ingeniero Civil graduado de la Pontificia Universidad Católica del Perú en Lima con estudios de postgrado en Manejo e Ingeniería de Recursos Hídricos (Programa WAREM) de la Universidad de Stuttgart con mención en Ingeniería de Aguas Subterráneas y Hidroinformática.

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