Changes between Version 37 and Version 38 of doc/app/initialization_parameters

Timestamp:

Sep 14, 2010 7:45:01 AM (14 years ago)

Author:

kanani

Comment:

--

doc/app/initialization_parameters

@@ -24 +24 @@
 }}}
 {{{#!td style="vertical-align:top; text-align:left;style="width: 100px"
-''.F.''
+.F.
 }}}
 {{{#!td
 Parameter to switch on ocean runs.\\\\
 By default PALM is configured to simulate atmospheric flows. However, starting from version 3.3, '''ocean''' = ''.T.'' allows simulation of ocean turbulent flows. Setting this switch has several effects:\\\\
-    * An additional prognostic equation for salinity is solved.
-    * Potential temperature in buoyancy and stability-related terms is replaced by potential density.
-    * Potential density is calculated from the equation of state for seawater after each timestep, using the algorithm proposed by Jackett et al. (2006, J. Atmos. Oceanic Technol., '''23''', 1709-1728).
-      So far, only the initial hydrostatic pressure is entered into this equation.
-    * z=0 (sea surface) is assumed at the model top (vertical grid index k=nzt on the w-grid), with negative values of z indicating the depth.
-    * Initial profiles are constructed (e.g. from [#pt_vertical_gradient pt_vertical_gradient] / [#pt_vertical_gradient_level pt_vertical_gradient_level]) starting from the sea surface, using surface values given by [#pt_surface pt_surface], [#sa_surface sa_surface], [#ug_surface ug_surface], and [#vg_surface vg_surface].
-    * Zero salinity flux is used as default boundary condition at the bottom of the sea.
+    * An additional prognostic equation for salinity is solved.\\
+    * Potential temperature in buoyancy and stability-related terms is replaced by potential density.\\
+    * Potential density is calculated from the equation of state for seawater after each timestep, using the algorithm proposed by Jackett et al. (2006, J. Atmos. Oceanic Technol., '''23''', 1709-1728).\\
+      So far, only the initial hydrostatic pressure is entered into this equation.\\
+    * z=0 (sea surface) is assumed at the model top (vertical grid index k=[#nzt nzt] on the w-grid), with negative values of z indicating the depth.\\
+    * Initial profiles are constructed (e.g. from [#pt_vertical_gradient pt_vertical_gradient] / [#pt_vertical_gradient_level pt_vertical_gradient_level]) starting from the sea surface, using surface values given by [#pt_surface pt_surface], [#sa_surface sa_surface], [#ug_surface ug_surface], and [#vg_surface vg_surface].\\
+    * Zero salinity flux is used as default boundary condition at the bottom of the sea.\\
     * If switched on, random perturbations are by default imposed to the upper model domain from zu(nzt*2/3) to zu(nzt-3).\\\\
 Relevant parameters to be exclusively used for steering ocean runs are [#bc_sa_t bc_sa_t], [#bottom_salinityflux bottom_salinityflux], [#sa_surface sa_surface], [#sa_vertical_gradient sa_vertical_gradient], [#sa_vertical_gradient_level sa_vertical_gradient_level], and [#top_salinityflux top_salinityflux].\\\\
-[#d3par d3par] [Section 4.4.2] gives an example for appropriate settings of these and other parameters neccessary for ocean runs.\\\\
+Section [#4.4.2 4.4.2] gives an example for appropriate settings of these and other parameters neccessary for ocean runs.\\\\
 '''ocean''' = ''.T.'' does not allow settings of [#timestep_scheme timestep_scheme] = '' 'leapfrog' '' or '' 'leapfrog+euler' '' as well as [#scalar_advec scalar_advec] = '' 'ups-scheme'.''
 }}}
@@ -102 +102 @@
 In order to speed-up performance, the Poisson equation for perturbation pressure (see [#psolver psolver]) can be called only at the last substep of multistep Runge-Kutta timestep schemes (see [#timestep_scheme timestep_scheme]) by setting '''call_psolver_at_all_substeps''' = ''.F.''. In many cases, this sufficiently reduces the divergence of the velocity field. Nevertheless, small-scale ripples (2-delta-x) may occur. In this case and in case of non-cyclic lateral boundary conditions, '''call_psolver_at_all_timesteps''' = ''.T.'' should be used. 
 }}}
-
+|----------------
+{{{#!td style="vertical-align:top"
+[=#cfl_factor '''cfl_factor''']
+}}}
+{{{#!td style="vertical-align:top"
+R
+}}}
+{{{#!td style="vertical-align:top"
+0.1, 0.8 or 0.9 (see right)
+}}}
+{{{#!td
+Time step limiting factor.\\\\
+In the model, the maximum allowed time step according to CFL and diffusion-criterion dt_max is reduced by [#dt dt] = dt_max * '''cfl_factor''' in order to avoid stability problems which may arise in the vicinity of the maximum allowed timestep. The condition ''0.0'' < '''cfl_factor''' < ''1.0'' applies.\\\\
+The default value of '''cfl_factor''' depends on the [#timestep_scheme timestep_scheme] used:\\\\
+For the third order Runge-Kutta scheme it is '''cfl_factor''' = ''0.9.''\\\\
+In case of the leapfrog scheme a quite restrictive value of '''cfl_factor''' = ''0.1'' is used because for larger values the velocity divergence significantly effects the accuracy of the model results. Possibly larger values may be used with the leapfrog scheme but these are to be determined by appropriate test runs.\\\\
+The default value for the Euler scheme is '''cfl_factor''' = ''0.8.''
+}}}
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@@ -390 +407 @@
 <insert explanation>
 }}}
+
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