Changeset 206 for palm/trunk/DOC
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- Oct 13, 2008 2:59:11 PM (16 years ago)
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palm/trunk/DOC/app/chapter_3.9.html
r197 r206 28 28 PALM includes a so-called turbulence recycling method which allows a 29 29 turbulent inflow with non-cyclic horizontal boundary conditions. The 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 s imulation 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>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> 31 31 is the horizontal average between the inflow boundary and the recycling 32 32 plane. The turbulent quantity A'(y,z) is then added to a mean inflow … … 39 39 horizontal average from this precursor run is used as the mean inflow 40 40 profile for the main run, the wall-normal velocity component must point 41 into the domain at every grid point and its magnitude should be large enough in order to guarantee an inflow even if a turbulence signal is added.</li><li>Since the main run requires ...</li><li>The 41 into the domain at every grid point and its magnitude should be large 42 enough in order to guarantee an inflow even if a turbulence signal is 43 added.<br></li><li>The 44 main run requires from the precursor run the mean profiles to 45 be used at the inflow. For this, the horizontally and temporally 46 averaged mean profiles as provided with the standard PALM output are 47 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>, 48 etc. for the precursor run appropriately, so that an output is done at 49 the end of the precursor run. The profile information is then contained 50 in the restart (binary) file created at the end of the precursor run 51 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>The 42 52 main run has to read the binary data from the precursor run .... 43 53 set bc_lr = 'dirichlet/radiation' ...
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