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| 25 | <h3 style="line-height: 100%;">3.9 Setup for turbulent inflow</h3> |
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| 26 | |
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| 27 | <p style="line-height: 100%;">Starting from version 3.5 |
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| 28 | PALM includes a so-called turbulence recycling method which allows a |
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| 29 | turbulent inflow with non-cyclic horizontal boundary conditions. The |
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| 30 | method follows the one described by Lund et al. (1998, J. Comp. Phys., <span style="font-weight: bold;">140</span>, 233-258), modified by Kataoka and Mizuno (2002, Wind and Structures, <span style="font-weight: bold;">5</span>, 379-392). The method is switched on by setting the initial parameter <a href="chapter_4.1.html#turbulent_inflow">turbulent_inflow</a> = <span style="font-style: italic;">.TRUE.</span>.</p><p style="line-height: 100%;">The turbulent signal A'(y,z) to be imposed at the left inflow boundary is taken from the same simulation at a fixed distance x<sub>r</sub> from the inflow (given by parameter <a href="chapter_4.1.html#recycling_width">recycling_width</a>): A'(y,z) = A(x<sub>r</sub>,y,z) - <span style="font-weight: bold;">A(z)</span>, where <span style="font-weight: bold;">A(z)</span> |
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| 31 | is the horizontal average between the inflow boundary and the recycling |
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| 32 | plane. The turbulent quantity A'(y,z) is then added to a mean inflow |
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| 33 | profile a(z) which is the horizontal (and temporal) average as |
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| 34 | calculated from a precursor run. This is done after each timestep.</p><p style="line-height: 100%; font-weight: bold;">So far (09/16/08), a turbulent signal is imposed to all prognostic variables except humidity (passive scalar) and salinity!</p><p style="line-height: 100%;">In |
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| 35 | order to avoid a continous growth of the turbulent layer with time, the |
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| 36 | height up to which turbulence is recycled is limited by parameter <a href="chapter_4.1.html#inflow_damping_height">inflow_damping_height</a>. By default, this height is calculated and taken from the precursor run. </p>The following tries to give a short recipe about how to create a proper setup for using the turbulence recycling method:<br><br><ul><li>A |
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| 37 | precursor run with cyclic horizontal boundary conditions has to be |
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| 38 | carried out in order to create a (quasi-) stationary state. Since the |
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| 39 | horizontal average from this precursor run is used as the mean inflow |
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| 40 | profile for the main run, <span style="font-weight: bold;">the |
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| 41 | wall-normal velocity component must point |
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| 42 | into the domain at every grid point and its magnitude should be large |
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| 43 | enough in order to guarantee an inflow even if a turbulence signal is |
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| 44 | added</span>.<br></li><li>The |
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| 45 | main run requires from the precursor run the mean profiles to |
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| 46 | be used at the inflow. For this, the horizontally and temporally |
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| 47 | averaged mean profiles as provided with the standard PALM output are |
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| 48 | used. The user has to set parameters <a href="chapter_4.2.html#dt_data_output_pr">dt_data_output_pr</a>, <a href="chapter_4.2.html#averaging_interval">averaging_interval</a>, |
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| 49 | etc. for the precursor run appropriately, so that an output is done <span style="font-weight: bold;">at |
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| 50 | the end</span> of the precursor run. The profile information is then contained |
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| 51 | in the restart (binary) file created at the end of the precursor run |
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| 52 | and can be used by the main run. <span style="font-weight: bold;">It is very important that the mean profiles at the end of the precursor run are in a stationary or quasi-stationary state</span>, because otherwise it may not be justified to use them as constant profiles at the inflow. <span style="font-weight: bold;">Also, turbulence at the end of the precursor run should be fully developed. </span>Otherwise, the main run would need an additional spinup-time at the beginning to get the turbulence to its final stage.<br></li><li>In order to read the binary data from the precursor run, parameter <a href="chapter_4.1.html#initializing_actions">initializing_actions</a> = <span style="font-style: italic;">'read_data_for_recycling'</span> has to be set in the main run. .... |
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| 53 | set bc_lr = 'dirichlet/radiation' ... |
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| 54 | conserve_volume_flow = .TRUE. ? ....</li><li>The main run allows to use a larger domain along x and y than in the precursor run ...</li><li>Recycling width should be equal to the domain size of the precursor run (or larger?)</li></ul><pre style="line-height: 100%;"><font style="font-size: 10pt;" size="2">#</font><br><font style="font-size: 10pt;" size="2">RUN_CONTROL<span style="font-weight: bold;">_O</span></font><font style="font-size: 10pt;" size="2"> out:loc:tr d3<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/MONITORING <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">rc</font><br><font style="font-size: 10pt;" size="2">HEADER</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> out:loc:tr d3<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/MONITORING <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">header</font><br><font style="font-size: 10pt;" size="2">PLOT1D_PAR<span style="font-weight: bold;">_O</span></font><font style="font-size: 10pt;" size="2"> out:loc:tr pr<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/OUTPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">pr_par</font><br><font style="font-size: 10pt;" size="2">PLOT1D_DATA</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> out:loc:tr pr<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/OUTPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">pr_in</font><br></pre><br><hr> |
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| 59 | <p style="line-height: 100%;"><i>Last |
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| 60 | change: </i> $Id: chapter_3.9.html 220 2008-12-18 07:00:36Z raasch $</p> |
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