126 lines
4.6 KiB
TeX
126 lines
4.6 KiB
TeX
\chapter{OlaFlow}
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\section{2D Model}
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A 2Dv model was built on a small domain around the breakwater (\SI{250}{\m}
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from the crest).
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A tool that allows mapping the output fields from swash to the initial fields
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in olaFlow was built. Alpha.water and U fields are mapped from swash to
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olaFlow.
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Boundary conditions are set using the output from the swash model.
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A regular mesh is generated and snapped to the bathymetry (mesh resolution: \SI{.5}{\m}).
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Simulation is run for 400 seconds using the largest wave from the swash model with the buoy spectrum as an input
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(\autoref{fig:wave}).
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\begin{figure}
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\centering
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\includegraphics{wave.pdf}
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\caption{Boundary condition for olaflow model.}\label{fig:wave}
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\end{figure}
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Results are plotted using python \autoref{fig:resola}.
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\begin{figure}
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\centering
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\includegraphics{resola.pdf}
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\caption{Results from olaFlow model.}\label{fig:resola}
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\end{figure}
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\subsection{Porosity parameters}
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Several parameters should be calibrated in order to accurately model the porous media: $a$, $b$ and $c$ are friction
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parameters in Forcheimer's equation; D50 is the median diameter of the elements constituting the porous media; $p$ is
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the porosity of the media.
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7 cases were run with the values in \autoref{tab:porotest}.
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\begin{table}
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\centering
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\begin{tabular}{cccccc}
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\toprule
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\textbf{Case} & $a$ & $b$ & $c$ & D50 (\si{\m}) & $\phi$ \\
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\midrule
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\textbf{0} & \num{50} & \num{1.2} & \num{0.34} & \num{4} & \num{0.4} \\
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\textbf{1} & \intersemibold\num{0} & \num{1.2} & \num{0.34} & \num{4} & \num{0.4} \\
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\textbf{2} & \intersemibold\num{5000} & \num{1.2} & \num{0.34} & \num{4} & \num{0.4} \\
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\textbf{3} & \num{50} & \intersemibold\num{0} & \num{0.34} & \num{4} & \num{0.4} \\
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\textbf{4} & \num{50} & \intersemibold\num{3.0} & \num{0.34} & \num{4} & \num{0.4} \\
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\textbf{5} & \num{50} & \num{1.2} & \num{0.34} & \intersemibold\num{2} & \num{0.4} \\
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\textbf{6} & \num{50} & \num{1.2} & \num{0.34} & \num{4} & \intersemibold\num{0.25} \\
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\bottomrule
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\end{tabular}
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\caption{Test cases for porosity parameters.}\label{tab:porotest}
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\end{table}
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Some results are displayed in \autoref{fig:diff} and \autoref{fig:diff2}. No major differences are noticable
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between cases (excepted for case 3, where $b=0$).
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\begin{figure}
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\centering
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\includegraphics{diff.pdf}
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\caption{Tests for porosity parameters; water - air border at \SI{-50}{\m}.}\label{fig:diff}
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\end{figure}
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\begin{figure}
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\centering
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\includegraphics{diff2.pdf}
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\caption{Tests for porosity parameters; water - air border at \SI{-20}{\m}.}\label{fig:diff2}
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\end{figure}
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Another run with a different value for $b$ was made (\autoref{tab:porotestb}). Results are in \autoref{fig:diff3b}.
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The value of $b$ seems to have a major effect how wave energy is dissipated / how waves break, as seen in
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\autoref{fig:diff3b175}.
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\begin{table}
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\centering
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\begin{tabular}{cccccc}
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\toprule
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\textbf{Case} & $a$ & $b$ & $c$ & D50 (\si{\m}) & $\phi$ \\
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\midrule
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\textbf{0} & \num{50} & \num{1.2} & \num{0.34} & \num{4} & \num{0.4} \\
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\textbf{1} & \num{50} & \intersemibold\num{0} & \num{0.34} & \num{4} & \num{0.4} \\ % 3
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\textbf{2} & \num{50} & \intersemibold\num{0.2} & \num{0.34} & \num{4} & \num{0.4} \\ % 3b
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\bottomrule
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\end{tabular}
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\caption{Test cases for porosity parameters.}\label{tab:porotestb}
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\end{table}
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\begin{figure}
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\centering
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\includegraphics{diff3b.pdf}
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\caption{Tests for porosity parameters; water - air border at \SI{-20}{\m}.}\label{fig:diff3b}
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\end{figure}
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\begin{figure}
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\centering
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\includegraphics{diff3b175.pdf}
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\caption{Tests for porosity parameters; water - air border at \SI{175}{\s}.}\label{fig:diff3b175}
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\end{figure}
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\subsection{Turbulence model}
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A case with the $k-\omega$ SST turbulence model was run to compare with the $k-\varepsilon$ model.
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Results displayed in \autoref{fig:sst}. Significant differences are found between both models.
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Wave breaking as expected using SST model (\autoref{fig:sst175}). See
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\url{https://public.edgarpierre.fr/anim_olaflow_kom.mp4}
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\begin{figure}
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\centering
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\includegraphics{diffsst.pdf}
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\caption{$x=\SI{-50}{\m}$. Case 1: $k-\varepsilon$ model; case 2: $k-\omega$ SST model.}\label{fig:sst}
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\end{figure}
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\begin{figure}
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\centering
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\includegraphics{diffsst175.pdf}
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\caption{$t=\SI{175}{\s}$. Case 1: $k-\varepsilon$ model; case 2: $k-\omega$ SST model.}\label{fig:sst175}
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\end{figure}
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\subsection{Results}
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Maximum flow velocity is displayed in \autoref{fig:maxu}.
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\begin{figure}
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\centering
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\includegraphics{maxu.pdf}
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\caption{Maximum velocity.}\label{fig:maxu}
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\end{figure}
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The flow reaches \SIrange{15}{20}{\m\per\s} velocity, which is in accordance with results from \textcite{amir}.
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