Let's suppose such a case, I added two variables, say, u & v to the
equation_system
with the same Fetype and order (LAGRANGE & SECOND, resp.). Then LIbmesh will
take
them into a single Variable Group automatically acoording to these two
properties.
I don't know how to deal with them separatelyby user yet.
Anyway, in this case if I'd like apply the Dirichlet BC for these components,
I have to apply them simultaneously, like
ParsedFunction("{4*y*(1-y)}{0.0}") for vector<uint> var_index[2] (which is
(0,1) here)
and set<uint> boundary_ids (which is 1 for my inlet).
When we check the system.print_info() we see as follows
EquationSystems
n_systems()=1
System #0, "Navier-Stokes"
Type "TransientNonlinearImplicit"
Variables={ "u" "v" } "p" //here is what I mean
Finite Element Types="LAGRANGE", "JACOBI_20_00" "LAGRANGE", "JACOBI_20_00"
Infinite Element Mapping="CARTESIAN" "CARTESIAN"
Approximation Orders="SECOND", "THIRD" "FIRST", "THIRD"
n_dofs()=4946
...
This is confirmed in my last test, although the code does work perfectly now.
By the way your remarks on the ConstFunction only available for multi-component
identical values was also
confirmed in my code now. So I think up to now, most problems I met are due to
my misunderstanding of the mechnism inside LibMesh, not the package itself.
Many thanks,
Zhenyu
------------------ Original ------------------
From: "Roy Stogner";<[email protected]>;
Date: Apr 1, 2015
To: "grandrabbit"<[email protected]>;
Cc: "libmesh-users"<[email protected]>;
Subject: Re: [Libmesh-users] How to properly call ParsedFunction
On Tue, 31 Mar 2015, grandrabbit wrote:
> As I can undertand now, the usage of ParsedFunction is conditional,
Yes.
> depending on if the boundary condition will be applied on a single variable or
> a variable group.
Not quite. It depends on what the index is of the variable you want
to apply it on. If your variables are ordered "u,v,p" then you can
set u equal to "sin(x)". If they're "p,u,v" then you'd need to set u
equal to "{0}{sin(x)}".
The variable groups can affect the efficiency of a given variable
ordering, but they shouldn't affect the component indexing.
(in current code, anyway - we may eventually add some optional
"System::reindex_variables()" command to sort variables into fewer
groups)
---
Roy
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