Changes between Version 110 and Version 111 of doc/app/initialization_parameters

Timestamp:

Sep 15, 2010 4:06:11 PM (14 years ago)

Author:

kanani

Comment:

--

doc/app/initialization_parameters

@@ -1756 +1756 @@
 |----------------
 {{{#!td style="vertical-align:top"
+[=#dt '''dt''']
+}}}
+{{{#!td style="vertical-align:top"
+R
+}}}
+{{{#!td style="vertical-align:top"
+variable
+}}}
+{{{#!td
+Time step for the 3d-model (in s).\\\\
+By default, (i.e. if a Runge-Kutta scheme is used, see [#timestep_scheme timestep_scheme]) the value of the time step is calculating after each time step (following the time step criteria) and used for the next step.\\\\
+If the user assigns '''dt''' a value, then the time step is fixed to this value throughout the whole run (whether it fulfills the time step criteria or not). However, changes are allowed for restart runs, because '''dt''' can also be used as a [../d3par run parameter].\\\\
+In case that the calculated time step meets the condition\\\\
+      '''dt''' < 0.00001 * [#dt_max dt_max] (with dt_max = 20.0)\\\\
+the simulation will be aborted. Such situations usually arise in case of any numerical problem / instability which causes a non-realistic increase of the wind speed.\\\\
+A small time step due to a large mean horizontal windspeed speed may be enlarged by using a coordinate transformation (see [#galilei_transformation galilei_transformation]), in order to spare CPU time.\\\\
+If the leapfrog timestep scheme is used (see [#timestep_scheme timestep_scheme]) a temporary time step value dt_new is calculated first, with dt_new = [#cfl_factor cfl_factor] * dt_crit where dt_crit is the maximum timestep allowed by the CFL and diffusion condition. Next it is examined whether dt_new exceeds or falls below the value of the previous timestep by at least +5 % / -2%. If it is smaller, '''dt''' = dt_new is immediately used for the next timestep. If it is larger, then '''dt''' = 1.02 * dt_prev (previous timestep) is used as the new timestep, however the time step is only increased if the last change of the time step is dated back at least 30 iterations. If dt_new is located in the interval mentioned above, then '''dt''' does not change at all. By doing so, permanent time step changes as well as large sudden changes (increases) in the time step are avoided.
+}}}
+|----------------
+{{{#!td style="vertical-align:top"
 [=#dt_pr_1d '''dt_pr_1d''']
 }}}
@@ -2606 +2626 @@
 ||='''Parameter Name'''  =||='''[../fortrantypes FORTRAN]\\[../fortrantypes Type]'''  =||='''Default\\Value'''  =||='''Explanation'''  =||
 |----------------
-{{{#!td style="vertical-align:top; text-align:left;width: 150px"
-[=# '''''']
-}}}
-{{{#!td style="vertical-align:top; text-align:left;style="width: 50px"
-
-}}}
-{{{#!td style="vertical-align:top; text-align:left;style="width: 75px"
-
-}}}
-{{{#!td
-
-}}}
-|----------------
-{{{#!td style="vertical-align:top"
-[=#<insert_parameter_name> '''<insert_parameter_name>''']
-}}}
-{{{#!td style="vertical-align:top"
-<insert type>
-}}}
-{{{#!td style="vertical-align:top"
-<insert value>
-}}}
-{{{#!td
-<insert explanation>
-}}}
+{{{#!td style="vertical-align:top;width: 150px"
+[=#alpha_surface '''alpha_surface''']
+}}}
+{{{#!td style="vertical-align:top;width: 50px"
+R
+}}}
+{{{#!td style="vertical-align:top;width: 75px"
+0.0
+}}}
+{{{#!td
+Inclination of the model domain with respect to the horizontal (in degrees).\\\\
+By means of '''alpha_surface''' the model domain can be inclined in x-direction with respect to the horizontal. In this way flows over inclined surfaces (e.g. drainage flows, gravity flows) can be simulated. In case of '''alpha_surface''' /= ''0'' the buoyancy term appears both in the equation of motion of the u-component and of the w-component.\\\\
+An inclination is only possible in case of cyclic horizontal boundary conditions along x '''AND''' y (see [#bc_lr bc_lr] and [#bc_ns bc_ns]) and [#topography topography] = '' 'flat'.''\\\\
+Runs with inclined surface still require additional user-defined code (see [[chapter 3.5]]) as well as modifications to the default code. Please ask the PALM developer group.
+}}}
+