Changes between Version 320 and Version 321 of doc/app/initialization_parameters

Timestamp:

Mar 21, 2017 11:12:05 AM (8 years ago)

Author:

hellstea

Comment:

--

doc/app/initialization_parameters

@@ -1359 +1359 @@
 In case of nested run, the default value of '''bc_p_t''' in the nest domains is not '' 'dirichlet' '' but '' 'neumann' '' instead. For the root domain of a nested run the default is '' 'dirichlet' '' as usually.\\\\
 '''Note:'''\\
-The nest-domain default boundary conditions for perturbation pressure lead to Poisson problem with all-Neumann boundary condition. This means that the solution is only determined up to a constant. In other words, the average value of the pressure remains arbitrary. This implies that the convergence rate is usually somewhat lower than when Dirichlet condition is used at least on one of the boundaries. Users using the nesting system should pay attention to this and adjust the steering parameters of the multigrid solver carefully to achieve sufficient convergence without sacrificing too much computing time for the perturbation-pressure solution. 
+The nest-domain default boundary conditions for perturbation pressure lead to Poisson problem with all-Neumann boundary condition. This means that the solution is only determined up to a constant. In other words, the average value of the pressure remains arbitrary. This implies that the convergence rate is usually somewhat lower than when Dirichlet condition is used at least on one of the boundaries. The average value of the perturbation pressure can be forced to a given value, but according to tests, it does not improve the convergence rate at all. 
+Users using the nesting system should pay attention to this and adjust the steering parameters of the multigrid solver carefully to achieve sufficient convergence without sacrificing too much computing time for the perturbation-pressure solution. 
 }}}
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