source: palm/trunk/TUTORIAL/SOURCE/topography.tex @ 1079

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\institute{Institut fÌr Meteorologie und Klimatologie, Leibniz UniversitÀt 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>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_1.png}
      \includegraphics<2>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_2.png}
      \includegraphics<3>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_3.png}
      \includegraphics<4>[width=\textwidth]{topography_figures/technical_implementation_grid/technical_implementation_grid_4.png}
      \includegraphics<5>[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 are interpolated.}
      \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}
      \begin{itemize}
         \item{Upstream of obstacle walls}
         \item{Due to second-order finite difference advection scheme}
         \item{Model remains stable throughout the simulation}
      \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>[width=0.5\textwidth]{topography_figures/control_parameters_1.png}
   \includegraphics<2>[width=0.5\textwidth]{topography_figures/control_parameters_2.png}
   \includegraphics<3>[width=0.5\textwidth]{topography_figures/control_parameters_3.png}
   \includegraphics<4>[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}