Report: the end?
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report/fig/U.pgf
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report/fig/U.pgf
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report/fig/p.pgf
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@ -103,7 +103,7 @@ turbulence: the $k-\varepsilon$ model and the $k-\omega$ sst model. The
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$k-\omega$ sst model should provide better results in situations where strong
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pressure gradients are present, at the cost of computing power.
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For the purposes of this initial sensibility study, the $k-\omega$ model will
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be used.
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be used, as it will allow for faster computation times.
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\subsection{Domain}
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The studied domain will be a two-dimensionnal vertical slice going through the
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@ -115,7 +115,7 @@ inside of the Saint-Jean-de-Luz bay, as shown in \autoref{fig:map}.
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\begin{figure}
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\centering
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\input{fig/map.pgf}
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\caption{Studied domain.}\label{fig:map}
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\caption{Studied domain and bathymetry (\cite{shomsjl}).}\label{fig:map}
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\end{figure}
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The bathymetry was generated using bathymetric data from the SHOM
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@ -154,6 +154,11 @@ $H=\SI{7.5}{\m}$. The wave equation is the following:
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\eta=H\left[\sech\sqrt{\frac 34\frac Hh\frac{x-ct}h}\right]^2
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\end{equation}
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The setup will be run for a duration of \SI{60}{\s}, using an adjustable
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timestep according to the cfd criteria. The results will be outputed at an
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interval of \SI{0.5}{\s}, which will provide enough accuracy to represent the
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studied case while providing a usable amount of data.
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\subsection{Porosity setup}
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The goal of the study is to find out the influence of the porosity parameters
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on the model results. Porosity in the olaFlow model is goverened by five
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@ -184,9 +189,69 @@ being the value that yielded the lowest error in the model calibration.
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\caption{Parameter values.}\label{tab:params}
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\end{table}
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\subsection{Post-processing}
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The results from the olaFlow model will be post-processed using Python. In
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order to analyze the sensibility of the model to the studied parameters,
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velocity and pressure sensors will be considered on the boundary of the
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porous part of the breakwater.
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\section{Results}
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\subsection{Pressure}
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\begin{figure}
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\centering
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\input{fig/p.pgf}
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\caption{Dynamic pressure computed using olaFlow.}\label{fig:p}
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\end{figure}
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Dynamic pressure was computed by olaFlow on the entire domain. The dynamic
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pressures obtained on the top side of the breakwater armour at
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$x=\SI{79.75}{\m}$ and $x=\SI{99.75}{\m}$ is plotted in \autoref{fig:p}.
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These results show that the porosity parameters that were modified have a minor
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influence on the dynamic pressure generated by the water flow. The maximum
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difference between the peak pressure for all cases is \SI{2}{\percent},
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which confirms the negligible impact of the porosity parameters on dynamic
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pressure.
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\subsection{Velocity}
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\begin{figure}
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\centering
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\input{fig/U.pgf}
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\caption{Flow velocity computed using olaFlow.}\label{fig:u}
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\end{figure}
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The flow velocity was plotted at the same positions as dynamic pressure in the
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previous section. The results are visible in \autoref{fig:u}.
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Immediatly, it is apparent that the conclusion for flow velocity will not be
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the same as for dynamic pressure. The difference between the velocity peaks for
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all cases reaches \SI{65}{\percent}, showing the importance of selecting
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adequate porosity parameters.
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The graphs also show that the most influencial parameter in this case seems to
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be porosity. The difference in peak flow velocity generated by the change in
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mean diameter is of around \SI{26}{\percent}, while a change in porosity yields
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a difference of around \SI{53}{\percent}.
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Contrarily to dynamic pressure, flow velocity computations are strongly
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impacted by changes in the porosity parameters.
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\cite{poncet2021characterization} showed that attempting to calibrate those
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results does not always yield the expected results, showing the necessity for
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additionnal measurement campaigns, or for a large enough calibration database
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to ensure the accuracy of a numerical model.
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\section{Conclusion}
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This project has shown that although the influence of porosity parameters on
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flow pressure is fairly minor, their influence on flow velocity is major.
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This shows the importance of using adequate values for these parameters in
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order to ensure an accurate representation of reality.
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Nevertheless, this study only focused on the mean diameter and porosity
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parameters, but several other model parameters may have an influence on the
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results. In particular, the friction parameters from the porosity model were
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not studied -- default values were used -- and the influence of the
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turbulence model was not considered. More work is still needed to evaluate the
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influence of those parameters on the accuracy of the model.
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\printbibliography
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\end{document}
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