Commit 488c9d44 authored by Douglas Serson's avatar Douglas Serson Committed by Spencer Sherwin
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Include description of DriverAdaptive in user guide

parent 828652a5
......@@ -918,7 +918,63 @@ Once these three files (the \inltt{Geometry} in \inlsh{Session.xml.gz}, the non
IncNavierStokesSolver Session.xml.gz Session.xml
\end{lstlisting}
\section{Adaptive polynomial order Session file configuration}
\label{SectionDriverAdaptive}
An adaptive polynomial order procedure is available for 2D and Quasi-3D simulations.
This procedure consists of the following steps:
\begin{itemize}
\item Advance the equations for a determined number of time steps
\item Use the sensor defined in equation \ref{eq:sensor} to
estimate an error measure (the variable used in the sensor can be specified).
The error is defined here as the square of the sensor.
\item Use the error to determine if the order in each element should be
increased by one, decreased by one, or left unaltered.
\item Project the solution in each element to the new polynomial order and use it as an
initial condition to restart the equation, repeating all steps a given number of times.
\end{itemize}
It is important to note that restarting the simulation after the refinement can be an
expensive operation (in a typical case 200 times the cost of a single time step). Therefore, the number
of steps between successive refinements needs to be carefully chosen, since if this value is too
low the procedure becomes inefficient, while if it is too high the refinement might not capture
accurately structures that are convected by the flow.
\subsection{Solver Info}
The use of the adaptive polynomial order procedure
is enforced through the definition of the \inltt{Driver} which has to be
\inltt{DriverAdaptive}.
\subsection{Parameters}
The following parameters can be specified in the \texttt{PARAMETERS} section of the session file:
\begin{itemize}
\item \inltt{NumSteps}: when using the adaptive order procedure, this parameter determines
the number of time steps between successive refinements.
\item \inltt{NumRuns}: this parameter defines the number of times the sequence of solving
the equation and refining is performed. Therefore,
the total number of time steps in the simulation is $NumSteps \times NumRuns$.
\item \inltt{AdaptiveMaxModes}: sets the maximum number of modes (in each direction)
that can be used in an element during the adaptive procedure. The solution will not be
refined beyond this point, even if the error is higher than the tolerance. Default value: 12.
\item \inltt{AdaptiveMinModes}: sets the minimal number of modes (in each direction)
that can be used in an element during the adaptive procedure. Default value: 4.
\item \inltt{AdaptiveUpperTolerance}: defines a constant tolerance. The polynomial order
in an element is increased whenever the error is higher than this value. This can be replaced
by a spatially-varying function, as described below. Default value: $10^{-6}$.
\item \inltt{AdaptiveLowerinModes}: defines a constant tolerance. The polynomial order in an
element is decreased whenever the error is lower than this value. This can also be replaced
by a spatially-varying function. Default value: $10^{-8}$.
\item \inltt{AdaptiveSensorVariable}: integer defining which variable will be considered when calculating
the error. For example, if this parameter is set to $1$ in the Incompressible Navier-Stokes Solver,
the error will be estimated using the $v$ velocity. Default value: $0$.
\end{itemize}
\subsection{Functions}
Spatially varying tolerances can be specified by defining the functions \inltt{AdaptiveLowerinModes} and/or \inltt{AdaptiveUpperTolerance}. In this case, the tolerance in an element is taken as the average of the function in the quadrature points of the element. If these functions are defined, the values set for the tolerances in the \texttt{PARAMETERS} section are ignored.
\section{Examples}
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