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\institute{Institut für Meteorologie und Klimatologie, Leibniz Universität Hannover}
\date{last update: \today}
\event{PALM Seminar}
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\title[PALM - Using Topography]{PALM - Using Topography}
\author{Siegfried Raasch}

% Notes:
% jede subsection bekommt einen punkt im menu (vertikal ausgerichtet.
% jeder frame in einer subsection bekommt einen punkt (horizontal ausgerichtet)
\begin{document}
% Folie 1
\begin{frame}
\titlepage
\end{frame}

% Folie 2
\begin{frame}
   \frametitle{Contents – Using Topography (I)}
   \begin{itemize}
      \item{Purpose of topography in PALM} 
      \item{Definition}
      \item{Realization}
      \begin{itemize}
         \item{Physical concept}
         \item{Technical / numerical implementation}
      \end{itemize}
      \item{Strengths and limitations}
      \item{Control parameters}
      \begin{itemize}
         \item{Required / optional topography parameters}
         \item{Topography-related general control parameters}
         \begin{itemize}
            \item{Suitable driving methods, initial and boundary conditions}
            \item{Pressure solver}
         \end{itemize}
      \end{itemize}
      \item{Data output}
   \end{itemize}
\end{frame}

% Folie 3
\begin{frame}
   \frametitle{Purpose of Topography}
   \begin{itemize}
      \item{Optional feature to simulate flow around/above obstacles}
      \par\bigskip
      \item{Application fields}
      \begin{itemize}
         \item{Urban meteorology, wind engineering}
         \item{Mesoscale meteorology}
         \item{Oceanography}
         \item{...}
      \end{itemize} 
   \end{itemize}
\end{frame}

% Folie 4
\begin{frame}
   \frametitle{Definition}   
   \begin{itemize}
      \item{The topography definition in PALM covers solid, impermeable, fixed flow obstacles with a volume of at least one grid box.}
      \par\bigskip
      \item{The following qualifies as topography: \textcolor{green!50!black!100}{\checkmark}}      
      \begin{itemize}
         \footnotesize
         \item{Human-made obstacles (buildings)}
         \item{Natural obstacles (hills, mountains)}
      \end{itemize}
      \par\bigskip
      \item{The following does NOT qualify as topography: \textcolor{red}{$\times$}}
      \begin{itemize}
         \footnotesize
         \item{\begin{tabbing}Permeable obstacles (vegetation) $\}$  \= Parameterization options in PALM: \\
                                                                     \> canopy model, local roughness length  \end{tabbing} } 
         \item{Small obstacles (signposts)}
         \item{Moving obstacles (vehicles)}                                                    
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 5
\begin{frame}
   \frametitle{Realization - Physical Concept}
   \scriptsize
   \begin{columns}[c]
   \column{0.8\textwidth}
      \begin{itemize}
         \item{Flow cannot enter topography and is forced around/above it.}
      \end{itemize}
   \column{0.2\textwidth}
   \end{columns}
   \begin{columns}[c]
   \column{0.6\textwidth}
      \begin{itemize}
         \item{Grid boxes are}
         \begin{itemize}
            \item{\begin{minipage}{0.1\textwidth} 
                     \includegraphics[width=0.7\textwidth]{topography_figures/physical_concept_small1.png}
                  \end{minipage}
                  \begin{minipage}{0.5\textwidth} \scriptsize
                     \par\medskip
                     100\% free fluid, \\
                  \end{minipage}}
            \item{\begin{minipage}{0.1\textwidth}
                     \includegraphics[width=0.7\textwidth]{topography_figures/physical_concept_small2.png}
                  \end{minipage}
                  \begin{minipage}{0.5\textwidth} \scriptsize
                     100\% fluid adjacent to an obstacle, or
                  \end{minipage}}     
            \item{\begin{minipage}{0.1\textwidth} 
                     \includegraphics[width=0.7\textwidth]{topography_figures/physical_concept_small3.png}
                  \end{minipage}
                  \begin{minipage}{0.5\textwidth} \scriptsize
                     \par\medskip
                     100\% obstacle. \\
                  \end{minipage}}             
         \end{itemize}
         \item{No-slip boundary condition}
         \begin{itemize}
            \item{\scriptsize Wall-normal velocity component is zero at obstacle surface \textbf{\textcolor{blue}{---------}}}
         \end{itemize}
         \par\bigskip
         \item{\begin{minipage}{0.75\textwidth}  \scriptsize
                  Local surface layer for the first grid box \\adjacent to each obstacle surface
               \end{minipage}
               \begin{minipage}{0.1\textwidth}
                  \includegraphics[width=0.7\textwidth]{topography_figures/physical_concept_small2.png}
               \end{minipage}}
         \par\smallskip
         \begin{itemize}
            \item{\scriptsize Neutral Monin-Obukhov similarity}
         \end{itemize}
      \end{itemize}
   \column{0.4\textwidth}
      \includegraphics[width=\textwidth]{topography_figures/physical_concept.png}
   \end{columns}
\end{frame}

% Folie 6
\begin{frame}
   \frametitle{Realization - \\ Numerical /Technical Implementation (I)}
   \small
   \begin{columns}[c]
   \column{0.5\textwidth}
      \begin{itemize}
         \item{Obstacles must be surface-mounted}
         \item{Overhanging structures \textcolor{blue}{$\times$}, holes \textcolor{red}{$\times$} etc. are not permitted.}
         \begin{itemize}
            \footnotesize
            \item{This simplification allows extra performance optimization by reducing the 3D obstacle dimension to a "'2.5D"' dimension.}
            \item{"'2.5D"' means that each horizontal grid cell is assigned only one height level.}
            \item{This conforms to the "'2.5D"' format of Digital Elevation Models (DEM).}
         \end{itemize}
      \end{itemize}     
   \column{0.4\textwidth}
      \par\medskip
      \includegraphics[width=1.1\textwidth]{topography_figures/technical_implementation.png}
   \end{columns}
\end{frame}

% Folie 7
\begin{frame}
   \frametitle{Realization - \\ Numerical /Technical Implementation (II)}
   \begin{columns}[c]
   \column{0.4\textwidth}
      \footnotesize     
      The location of the wall-normal velocity component defines the location of the impermeable obstacle surface. \\
      \par\smallskip
      Obstacle surfaces that do not match the grid are approximated by grid boxes like a step-function. 
      \par\bigskip
      $\bullet$ scalars \\
      \textcolor{red}{$\bullet$ u (staggered)} \\
      \textcolor{green!40!black!100}{\textbf{+} v (staggered)}
%      \includegraphics[width=0.4\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_small1.png} \\
%      \includegraphics[width=0.6\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_small2.png} \\
%      \includegraphics[width=0.6\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_small3.png}
   \column{0.6\textwidth}
      \includegraphics<1|handout:0>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_1.png}
      \includegraphics<2|handout:0>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_2.png}
      \includegraphics<3|handout:0>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_3.png}
      \includegraphics<4|handout:0>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_4.png}
      \includegraphics<5|handout:1>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_5.png}
   \end{columns}
\end{frame}

% Folie 8
\begin{frame}
   \frametitle{Realization - \\ Numerical / Technical Implementation (III)}
   \footnotesize
   \textbf{Rastering GIS data: \dq from GIS data to ASCII raster data\dq}
   \begin{itemize}
      \item{In order to process topography from external data sources, the data must be made available 
            to PALM as a rastered ASCII file, e.g. example\_topo.} 
      \item{The layout of example\_topo must conform to the computational domain size and to the grid size dx and dy.}
      \item{The rastered height data of example\_topo are given in m above ground and do not need to match
            the vertical grid, since they will be interpolated, if required.}
      \par\bigskip
      \item{Software known to be able to perfom the rastering process of GIS data in vector and/or raster format to PALM raster format:}
      \begin{itemize}
         \item{ArcGIS (commercial)}
         \item{GRASS GIS (freeware)}
         \item{...? (please report to us)}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 9
\begin{frame}
   \frametitle{Realization – \\ Numerical / Technical Implementation (IV)}  
   \small
   \textbf{Potential issues}
   \begin{itemize}
      \item{Load imbalance} 
      \begin{itemize}
         \item{Leads to inefficient parallelization: \dq fast\dq CPU(s) must wait for \dq slow\dq CPU(s)}
         \item{Occurs if the CPUs do not share the same workload}
         \begin{itemize}
            \item{E.g. if topography is significantly heterogeneous in a large volume fraction of the computational domain}
         \end{itemize}
      \end{itemize}     
      \item{\dq 2 $\Delta$x\dq instabilities (only if Piacsek-Williams advection scheme is used)}
      \begin{itemize}
         \item{Upstream of obstacle walls}
         \item{Due to second-order finite difference advection scheme}
         \item{Model remains stable throughout the simulation}
         \item{The default Wicker-Skamarock scheme does not show any instabilities}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 10
\begin{frame}
   \frametitle{Summary: Strengths (+) and Limitations (–)}
   \small
   \begin{itemize}
      \item[+]{Horizontal and vertical surfaces can be exactly resolved (thanks to the finite difference Cartesian model architecture)}
      \item[+]{Optimization also for scalar computer architectures}
      \item[+]{Conforms with \dq 2.5D\dq format of Digital Elevation Models (DEM)} 
      \par\bigskip
      \item[-]{Obstacles must be surface-mounted}
      \item[-]{Grid boxes can only be 100\% fluid or 100\% obstacle \\ \par\smallskip
              \begin{footnotesize} Obstacle surfaces that do not match the grid are approximated by grid boxes like a step-function, which 
 	      modifies the real obstacle size \end{footnotesize}}
      \item[-]{Overhanging structures, holes etc. are not permitted due to the \dq 2.5D\dq format}
   \end{itemize}
\end{frame}

% Folie 11
\begin{frame}
   \frametitle{Take a Short Break... Urban Flow Visualization}
   \begin{columns}[c]
   \column{0.42\textwidth}
      \includegraphics<1>[width=\textwidth]{topography_figures/hannover_1.png}
      \href{.html}{\includegraphics<2>[width=\textwidth]{topography_figures/hannover_2.png}}
   \column{0.58\textwidth}
      Set-up: neutral boundary layer
      \begin{itemize}
         \item{Particle = passive tracer}
         \item{Colour $\sim$ particle height}
         \item{Tail length ~ particle velocity}         
      \end{itemize}      
      \par\bigskip
      \begin{itemize}
         \item{Flow past office tower:}
         \begin{itemize}
            \item{initially laminar: not yet an LES}
            \item{intermittent: different episodes}
         \end{itemize}
         \item{Broad street canyon flow:}
         \begin{itemize}
            \item{channeling}
            \item{low-level upstream flow}
         \end{itemize}
      \end{itemize}
   \end{columns}
\end{frame}

% Folie 12
\begin{frame}
   \frametitle{Required Topography Control Parameters}
    \footnotesize
   {\tt topography =} 
   \begin{itemize}
      \item{{\tt 'flat'} \hspace{3cm} no topography (default)}
      \item{{\tt 'single\_building'} \hspace{1.2cm} \textcolor{red}{generic} single building} 
      \item{{\tt 'single\_street\_canyon'} \hspace{0.4cm} \textcolor{red}{generic} single quasi-2D street canyon}
      \item{{\tt 'read\_from\_file'} \hspace{1.4cm} \textcolor{blue}{rastered} ASCII file, e.g. {\tt example\_topo}}
      \item{any other string \hspace{1.8cm} processed by user subroutine user\_init\_grid}
   \end{itemize}
   {\tt topography\_grid\_convention =}
   \begin{itemize}
      \item{{\tt '\textcolor{red}{cell\_edge}'} \hspace{2.2cm} default for \textcolor{red}{generic} topography: \textcolor{red}{$\leftrightarrow$}}
      \item{{\tt '\textcolor{blue}{cell\_center}'} \hspace{1.9cm} default for \textcolor{blue}{rastered} topography: \textcolor{blue}{$\bigcirc$ $\leftrightarrow$}} 
   \end{itemize}
   \includegraphics<1|handout:0>[width=0.5\textwidth]{topography_figures/control_parameters_1.png}
   \includegraphics<2|handout:0>[width=0.5\textwidth]{topography_figures/control_parameters_2.png}
   \includegraphics<3|handout:0>[width=0.5\textwidth]{topography_figures/control_parameters_3.png}
   \includegraphics<4|handout:1>[width=0.5\textwidth]{topography_figures/control_parameters_4.png}
\end{frame}

% Folie 13
\begin{frame}
   \frametitle{Optional Topography Control Parameters (I)}
   \small
   \textbf{Generic topography}    
   \scriptsize
   \begin{itemize}
      \item{topography = {\tt 'single\_building'}} 
      \begin{itemize}
         \scriptsize
         \item{building\_height = 50.0 \hspace{0.67cm} height of the building}
         \item{building\_length\_x = 50.0 \hspace{0.43cm} length of the building in x-direction}
         \item{building\_length\_y = 50.0 \hspace{0.43cm} length of the building in y-direction}
         \item{building\_wall\_left \hspace{1.4cm} (default is building centered in x-direction)}
         \item{building\_wall\_south \hspace{1.13cm} (default is building centered in y-direction)}
      \end{itemize}
      \item{topography = {\tt 'single\_street\_canyon'}}
      \begin{itemize}
         \scriptsize
         \item{canyon\_height = 50.0 \hspace{0.45cm} height of the canyon \\
               and}
         \item{canyon\_width\_x = 50.0 \hspace{0.3cm} implies canyon axis orientation in y-direction}
         \item{canyon\_wall\_left \hspace{1.17cm} (default is canyon centered in x-direction) \\
               or}
         \item{canyon\_width\_y = 50.0 \hspace{0.3cm} implies canyon axis orientation in x-direction}
         \item{canyon\_wall\_south \hspace{0.9cm} (default is canyon centered in y-direction)}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 14
\begin{frame}
   \frametitle{Optional Topography Control Parameters (II)}
   \scriptsize   
   \textbf{Rastered topography}\\
   \begin{minipage}{0.7\textwidth}
      \begin{itemize}
         \scriptsize
         \item{{\tt topography} = 'read\_from\_file'} 
         \begin{itemize}
            \footnotesize
            \item{requires an external ASCII file, e.g. {\tt example\_topo:}}
         \end{itemize}
      \end{itemize}
   \end{minipage}
   \begin{minipage}{0.2\textwidth}
      \includegraphics[width=0.5\textwidth]{topography_figures/optional_control_parameters_1.png}
   \end{minipage}
   \begin{center}
      \includegraphics[width=0.85\textwidth]{topography_figures/optional_control_parameters_2.png}
   \end{center}
   \begin{itemize}
      \item[]{}
      \begin{itemize} 
         \scriptsize         
         \item{layout must conform to domain size and grid size dx and dy.}
         \item{height data}
         \begin{itemize}
            \scriptsize
            \item{in m above ground (INTEGER or REAL)}
            \item{do not need to match the vertical grid}
         \end{itemize}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 15
\begin{frame}
   \frametitle{Optional Topography Control Parameters (III)}
   \small
   \textbf{Rastered topography}
   \begin{itemize}
      \item{{\tt topography} = 'read\_from\_file'}
      \par\smallskip
      \begin{itemize}
         \item{\textbf{mrun}-call: \\
               {\tt mrun ... -r 'd3\# ...'}}
         \par\medskip
         \item{{\tt .mrun.config:}}
      \end{itemize}
   \end{itemize}  
   \begin{center} \includegraphics[width=0.7\textwidth]{topography_figures/optional_control_parameters_3.png} \end{center}
\end{frame}

% Folie 16   
\begin{frame}
   \frametitle{General Control Parameters (I): Suitable Driving Methods}
   \scriptsize
   \begin{itemize}
      \item{\textbf{\dq Meteorological\dq set-up M: geostrophic wind / Coriolis force}}
      \begin{itemize}
         \scriptsize
         \item{Set {\tt omega $ \neq$ 0.0}}
         \item{Construct a non-zero profile of geostrophic wind $u_g$ and/or $v_g$ using {\tt ug\_surface}, {\tt ug\_vertical\_gradient}
               and {\tt ug\_vertical\_gradient\_level} and/or the respective parameter set for $v_g$}
      \end{itemize}
      \par\bigskip
      \item{\textbf{\dq Engineering\dq set-up E: direct external pressure gradient / no Coriolis force}}
      \begin{itemize}
         \scriptsize
         \item{Set {\tt omega = 0.0}}
         \item{Set-up E1: direct external pressure gradient that does not change with time 
		 (the bulk velocity fluctuates with time)}
         \begin{itemize}
            \scriptsize
            \item{Parameters: {\tt dp\_external}, {\tt dp\_smooth}, {\tt dp\_level\_b}, {\tt dpdxy}}
         \end{itemize}
         \item{Set-up E2: maintain a constant bulk velocity 
		 (the direct external pressure gradient fluctuates with time)}
         \begin{itemize}
             \scriptsize
             \item{Parameters: {\tt conserve\_volume\_flow}, {\tt conserve\_volume\_flow\_mode}, {\tt u\_bulk}, {\tt v\_bulk}}
         \end{itemize}
      \end{itemize}
      \par\bigskip
      \item{\textbf{\dq Thermal\dq set-up T: directly prescribe sensible heatflux}}
      \begin{itemize}
         \item[]{}
         \begin{itemize}
            \scriptsize
            \item{surface\_heatflux at ground level only} 
            \item{wall\_heatflux(0:4) at top/left/right/South/North obstacle face}
         \end{itemize}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 17
\begin{frame}
   \frametitle{General Control Parameters (II): Initialization}
   \scriptsize
   \begin{itemize}
      \item{\textbf{\dq Meteorological\dq set-up M }\\
            Initialize a non-zero profile of geostrophic wind $u_g$ and/or $v_g$ using}
      \begin{itemize}
         \scriptsize
         \item{{\tt initializing\_actions =} \textbf{'set\_constant\_profiles' (e.g. for convective BL)}}
         \begin{itemize}
            \scriptsize
            \item{Parameters: {\tt ug\_surface $ \neq $ 0.0} and/or {\tt vg\_surface $\neq $ 0.0}}
         \end{itemize}
         \item{{\tt initializing\_actions =} \textbf{'set\_1d-model\_profiles' (e.g. for neutral BL)}}
         \begin{itemize}
            \scriptsize
            \item{1D model prerun parameters with suffix {\tt \_1d} (e.g. {\tt end\_time\_1d}, {\tt damp\_level\_1d)}}
         \end{itemize}
      \end{itemize}  
      \par\bigskip
      \item{\textbf{\dq Engineering\dq set-up E} \\
            Good initialization may require a priori knowlegde, e.g. from previous test runs. 
            Here, {\tt ug\_}... and {\tt vg\_}... don't refer to geostrophic wind but to the initial wind profile.} 
      \begin{itemize}
         \scriptsize
         \item{{\tt initializing\_actions} = \textbf{'set\_constant\_profiles'}}
         \begin{itemize}
            \scriptsize
            \item{Parameter set: {\tt ug\_surface}, {\tt ug\_vertical\_gradient}[{\tt \_level}] and/or the respective set for $v_g$}
         \end{itemize}
         \item{{\tt initializing\_actions} = \textbf{'set\_1d-model\_profiles'}}
         \item{{\tt initializing\_actions} = \textbf{'by\_user' – processed by user\_init\_3d\_model}}
      \end{itemize}
      \par\bigskip
      \item{\textbf{\dq Thermal\dq set-up T} \\
            Any of the above may apply}
   \end{itemize}
\end{frame}

% Folie 18
\begin{frame}
   \frametitle{General Control Parameters (III): Boundary Conditions}
   \footnotesize
   \begin{itemize}
      \item{Lateral boundary conditions}
      \begin{itemize}
         \item{Cyclic / non-cyclic: cf. lecture on \dq non-cyclic boundary conditions\dq}
      \end{itemize} 
      \item{Bottom boundary conditions}
      \begin{itemize}
         \item{Cf. lecture on \dq numerics and boundary conditions\dq}
      \end{itemize}
      \item{Top boundary conditions}
      \begin{itemize}
         \footnotesize
         \item{\textbf{Channel}: {\tt bc\_uv\_t =} \textbf{'dirichlet\_0' (no-slip)}}
         \item{\textbf{Open channel}: {\tt bc\_uv\_t =} \textbf{'neumann' (slip)}}
         \item{\textbf{\dq Constant flux\dq layer} (not yet published): {\tt bc\_uv\_t =} \textbf{'neumann' (slip)} \\
                with set-up E1 where {\tt dp\_level\_b >> 0} and {\tt dp\_smooth = .T.}}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 19
\begin{frame}
   \frametitle{General Control Parameters (IV): Pressure Solver} 
   {\tt psolver =}
   \par\medskip
   \begin{itemize}
      \item{'poisfft' (FFT scheme)} 
      \begin{itemize}
         \item{Good performance for urban PALM version}
         \item{Cannot be used with non-cyclic boundary conditions}
      \end{itemize}
      \par\bigskip
      \item{'multigrid' (Multigrid scheme)}
      \begin{itemize}
         \item{Performance for very large number of grid points may be better than FFT}
         \item{This is the only possible choice for non-cyclic boundary conditions}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 20
\begin{frame}
   \frametitle{Data Analysis / Output – Some Considerations (I)}
   \scriptsize
   \begin{itemize}
      \item{How to get turbulence statistics?}
      \begin{itemize}
         \scriptsize
         \item{Phase averaging if a direction of homogeneity exists}
         \item{Temporal averaging}
         \item{Ensemble averaging}
      \end{itemize} 
      \item{Definition of turbulent fluctuations}\\
      \textbf{Spatial fluctuations:} deviation from representative instantaneous spatial average
      \begin{itemize}
         \scriptsize
         \item{PALM: many statistics calculated on-the-fly as time series, 1D vertical profiles}
         \item{Not suitable for topography unless a direction of homogeneity exists}
      \end{itemize}
      \textbf{Temporal fluctuations}: deviation from representative local temporal average
      \begin{itemize}
         \scriptsize
         \item{Suitable for all applications including topography}
         \item{Requires much hard disk space and post-processing CPU time}
         \item{PALM: not natively supported, but following procedure works:}
         \begin{itemize}
            \scriptsize
            \item{Collect time-series during the simulation (2D/3D data output or user-defined time series)}
            \item{Check for (quasi-)steady turbulent state and sufficient averaging time}
            \item{Calculate statistics by post-processing making use of the Reynolds decomposition: \\ \par\medskip
                  $\overline{w'\theta'} = \overline{w\theta} - \overline{w} \overline{\theta} $}
         \end{itemize}
      \end{itemize}    
   \end{itemize}
\end{frame}

% Folie 21
\begin{frame}
   \frametitle{Your Responsibility and Contribution}
   \footnotesize
   \par\medskip
   In most cases, a new parameter is added to PALM for one specific purpose.
   \par\bigskip
   Beyond this one purpose, each new parameter normally gives many other new feature/parameter combinations in PALM.
   We are unable to check all these combinations by ourselves and rely on your help!
   \par\bigskip
%    For example, the combination of topography and non-cyclic lateral boundary conditions has not yet been tested 
%    because both features have originally been introduced separately for different research projects.
%    \par\bigskip 
   Therefore, we ask you for your responsibility and contribution:
   \begin{itemize}
      \item{Please always check your PALM setup carefully. PALM is not a black box.} 
      \item{For example, design a simple case and test your expectation.}
      \item{Please report potential bugs – thank you!}
      \begin{itemize}
         \item{PALM developer team}
         \item{PALM user community (via trac-system)}
      \end{itemize}
   \end{itemize}
\end{frame}

% Folie 22
\begin{frame}
   \Large
   \begin{center} \textcolor{blue!90!black!100}{Topography - Scenario examples} \end{center}
\end{frame}

% Folie 23
\begin{frame}
   \frametitle{Set-up Scenario: Single Street Canyon (I)}
   \par\smallskip
   \textbf{Single quasi-2D street canyon in neutral open channel flow with constant bulk velocity}
   \par\smallskip
   \begin{itemize}
      \item{{\tt trunk/EXAMPLES/canyon/}}
      \begin{itemize}
         \item{Parameter file \hspace{2cm} {\tt example\_canyon\_p3d}}
         \item{Run-control file \hspace{1.78cm} {\tt example\_canyon\_rc}}
         \item{Some documentation \hspace{0.95cm} {\tt example\_canyon.odt}}
      \end{itemize}
   \end{itemize}
   \begin{center}
      \includegraphics[width=0.85\textwidth]{topography_figures/scenario_ssc_1.png}
   \end{center}
\end{frame}

% Folie 24
\begin{frame}
   \frametitle{Set-up Scenario: Single Street Canyon (II)}
   \textbf{The phase average makes use of homogeneity in y-direction:} \\
   {\tt section\_xz = -1}, {\tt data\_output = \textbf{'u\_xz\_av'}}, {\tt 'v\_xz\_av'}, {\tt 'w\_xz\_av'}
   \begin{center}
      \includegraphics[width=0.85\textwidth]{topography_figures/scenario_ssc_2.png}
   \end{center}
\end{frame}

% Folie 25
\begin{frame}
 \begin{tikzpicture}[remember picture, overlay]
      \node [shift={(6.5 cm, 5cm)}]  at (current page.south west)
         {%
         \begin{tikzpicture}[remember picture, overlay]
            \uncover<1>{\node at (0,-0.5) {\includegraphics[width=0.7\textwidth]{topography_figures/scenario_ssc_example_1.png}};}
            \uncover<2>{\node at (0,-0.5) {\includegraphics[width=0.7\textwidth]{topography_figures/scenario_ssc_example_2.png}};}
            \uncover<3->{\node at (0,-0.5) {\includegraphics[width=0.7\textwidth]{topography_figures/scenario_ssc_example_3.png}};}
            \uncover<4->{\node at (-3.5,-0.2) {\includegraphics[width=0.48\textwidth]{topography_figures/scenario_ssc_example_4.png}};}
            \uncover<5->{\node at (3.5,-0.2) {\includegraphics[width=0.38\textwidth]{topography_figures/scenario_ssc_example_5.png}};}
         \end{tikzpicture}
         };
  \end{tikzpicture}
\end{frame}

% Folie 26
\begin{frame}
   \frametitle{Set-up Scenario: Constant Flux Layer}
   \small
   \textbf{Single surface-mounted cube in neutral open channel flow with a constant flux layer}
   \begin{itemize}
      \item{{\tt trunk/EXAMPLES/constant\_flux\_layer/}}
      \begin{itemize}
         \footnotesize
         \item{Parameter file \hspace{2cm} {\tt example\_constant\_flux\_layer\_p3d}}
         \item{Run-control file \hspace{1.79cm} {\tt example\_constant\_flux\_layer\_rc}}
         \item{Some documentation \hspace{1.02cm} {\tt example\_constant\_flux\_layer.odt}}
      \end{itemize}
   \end{itemize}
   \begin{center}
      \includegraphics[width=0.85\textwidth]{topography_figures/scenario_cfl.png}
   \end{center}
\end{frame}

% Folie 27
\begin{frame}
 \begin{tikzpicture}[remember picture, overlay]
      \node [shift={(6.5 cm, 5cm)}]  at (current page.south west)
         {%
         \begin{tikzpicture}[remember picture, overlay]
            \uncover<1->{\node at (0,-0.5) {\includegraphics[width=0.7\textwidth]{topography_figures/scenario_cfl_example_1.png}};}
            \uncover<2->{\node at (-3.5,-0.2) {\includegraphics[width=0.45\textwidth]{topography_figures/scenario_cfl_example_2.png}};}
            \uncover<3->{\node at (3.5,-0.2) {\includegraphics[width=0.38\textwidth]{topography_figures/scenario_cfl_example_3.png}};}
         \end{tikzpicture}
         };
  \end{tikzpicture}
\end{frame}

% Folie 28
\begin{frame}
   \frametitle{Rules of Good Practise}
   \small
   \begin{itemize}
      \item{If you run PALM with topography, make sure that it is really LES...}
      \begin{itemize}
         \item{''Large eddies'' are ''small'' between obstacles}
         \begin{itemize}
            \item{use fine grid length to resolve turbulence there}
         \end{itemize}
         \item{Ratio of resolved to SGS fluxes}
      \end{itemize} 
      \item{Check for (quasi-)steady turbulent state and sufficient averaging time.}
      \begin{itemize}
         \item{Fluctuations of time series of E, E*, maximum velocity components etc.}
      \end{itemize}
      \item{Make sure that your PALM result is independent of numerical parameters such as domain size and grid size.}
      \begin{itemize}
         \item{Sensitivity studies}
      \end{itemize}
      \item{If you intend to do a comparison with some kind of reference data, it is essential to configure the set-up of PALM 
           in the same way as the reference experiment.}
      \begin{itemize}
         \item{For example, if you compare PALM with wind tunnel results, you have to follow the wind tunnel set-up for setting up PALM.}
      \end{itemize}
   \end{itemize}
\end{frame}

\end{document}