Difference between revisions of "Settling Sphere by Michael Alletto"

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* The '''second objective''' is to validate the overset methodology implemented into OpenFOAM with experiments. This is a mandatory step to estimate the uncertainty of a given simulation method. The uncertainty of a tool is connected to the risk not meeting a design criteria when this tool is employed in an industrial context.  
 
* The '''second objective''' is to validate the overset methodology implemented into OpenFOAM with experiments. This is a mandatory step to estimate the uncertainty of a given simulation method. The uncertainty of a tool is connected to the risk not meeting a design criteria when this tool is employed in an industrial context.  
  
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For this purpose the experimental setting by \cite{ten2002particle} was chosen to be simulated. The experimental settings consists in a rectangular box with dimensions of 100x100x160mm (in x-,y- and z-coordinate direction). Gravity points in negative z-direction. The lower part of the sphere was hanging 120mm from the bottom wall. The sphere had a diameter of 15mm and a density $\rho_s$ of 1120 $kg/m^3$. Different Re-numbers based on the free falling velocity  were measured (Re: 1.4, 4.1, 11.6 and 32.2). For this tutorial the lowest Re number was chosen. The variation of the Re-number in the experiments was achieved by choosing fluids with different fluid viscosities $\mu_f$. The same can be done here if  other Re-numbers have to be simulated. The setup can be seen in Figure \ref{fig:setup}.
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For this purpose the experimental setting by [1] was chosen to be simulated. The experimental settings consists in a rectangular box with dimensions of 100x100x160mm (in x-,y- and z-coordinate direction). Gravity points in negative z-direction. The lower part of the sphere was hanging 120mm from the bottom wall. The sphere had a diameter of 15mm and a density ρ_s of 1120 kg/m^3. Different Re-numbers based on the free falling velocity  were measured (Re: 1.4, 4.1, 11.6 and 32.2). For this tutorial the lowest Re number was chosen. The variation of the Re-number in the experiments was achieved by choosing fluids with different fluid viscosities μ_f. The same can be done here if  other Re-numbers have to be simulated. The setup can be seen in the figure below ('''missing''').
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[1] Ten Cate, A Nieuwstad, CH Derksen, JJ Van den Akker: Particle imaging velocimetry experiments and lattice-Boltzmann simulations on a single sphere settling under gravity, Physics of Fluids, 14(11), AIP, p. 4012-4025, 2002

Revision as of 03:51, 5 September 2019

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Sphere settling under the influence of gravity

Introduction

This tutorial has two main objectives:

  • The first objective is to show how to set up an overset simulation with OpenFOAM. The overset methods (also know as chimera method) is very useful if large body motions have to be simulated. It consists in a fixed background mesh and one or more disconnected mesh regions which are subject to large displacements. In order to couple the disconnected mesh regions, the flow variables are interpolated between the meshes. Inside each disconnected mesh region, the solution is calculated by means of the usual finite volume discretisation. The different mesh regions are usually not subject to topological changes which allows to maintain the original mesh quality.
  • The second objective is to validate the overset methodology implemented into OpenFOAM with experiments. This is a mandatory step to estimate the uncertainty of a given simulation method. The uncertainty of a tool is connected to the risk not meeting a design criteria when this tool is employed in an industrial context.

For this purpose the experimental setting by [1] was chosen to be simulated. The experimental settings consists in a rectangular box with dimensions of 100x100x160mm (in x-,y- and z-coordinate direction). Gravity points in negative z-direction. The lower part of the sphere was hanging 120mm from the bottom wall. The sphere had a diameter of 15mm and a density ρ_s of 1120 kg/m^3. Different Re-numbers based on the free falling velocity were measured (Re: 1.4, 4.1, 11.6 and 32.2). For this tutorial the lowest Re number was chosen. The variation of the Re-number in the experiments was achieved by choosing fluids with different fluid viscosities μ_f. The same can be done here if other Re-numbers have to be simulated. The setup can be seen in the figure below (missing).

[1] Ten Cate, A Nieuwstad, CH Derksen, JJ Van den Akker: Particle imaging velocimetry experiments and lattice-Boltzmann simulations on a single sphere settling under gravity, Physics of Fluids, 14(11), AIP, p. 4012-4025, 2002

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