mkDirBC2

mkDirBC2 - Specify Dirichlet boundary conditions

Calling sequence:

mkDirBC2(DBCeq, unknown_list, old_unknown_list, params_list,unkntestlist,testbsflist)

Parameters:

DBCeq - A list of equations specifying Dirichlet boundary conditions. Each entry in the list is an equation of the form u(x,y)=expr, where u(x,y) is a variable in unknown_list. For those variables in unknown_list, which do not appear in DBCeq, a default Dirichlet boundary condition is used. This is u(x,y) = qBCval, where qBCval is a predefined value which is specified with the mesh.
If one of the entries in DBCeq is SinglePoint(var), where var is one of the variables in unknown_list, a Dirichlet condition is applied at one single node, prescribing the variable to be zero at that node.

unknown_list - The list of unknowns as discussed above.

old_unknown_list - The list of unknowns at the previous timestep, as discussed above.

params_list - A list of scalar input parameters.

unkntestlist - A list of testfunction names that couple a certain testfunction with a certain unknown. The number of entries in unkntestlist must be the same as in unknown_list and old_unknown_list. The usage is the same as for the corresponding argument to mkFem2.

testbsflist - A list containing three entries, the first two being names of testfunctions, the last the name of a file that contins the definitions of the basefunctions. The two basefunction names are identified with the actual basefunctions via ordering and the name of this file, i.e., with testbsflist:=[v(x,y),q(x,y),`2DP2P1_gsq_bsf`], v(x,y) is P2 and q(x,y) is P1. The usage is the same as for the corresponding argument to mkFem2.

Synopsis:

Generates the code needed to specify Dirichlet boundary conditions for use with mixed formulations with two different basefunctions. Except for the last two arguments the function is the same as mkDirBC.
If the string 'qBCval' is encountered in DBCeq, it is replaced by a predefined value specified with the mesh. This gives a way of separating parts of the boundary with different Dirichlet conditions.
If one of the entries in DBCeq is SinglePoint(var), the value of that variable will be set to zero at one single node. This is useful for equations with only Neumann conditons, for which the solution is only determined up to an additive constant. Using SinglePoint(var) this additive constant is fixed (arbitrarily), and possible numerical problems are avoided.

Examples:

> #set up lists:

> eq_list:= [ueq,veq,pP0eq,pP1eq]:

> unknown_list:= [u(x,y),v(x,y),p(x,y),p1(x,y)]:

> old_unknown_list:= [uo(x,y),vo(x,y),po(x,y),p1o(x,y)]:

> params_list:= [Diffusivity,bigQ,BCpara]:

> unkntestlist:=[test(x,y),test(x,y),q(x,y),q(x,y)];

> unkntestlist := [test(x, y), test(x, y), q(x, y), q(x, y)]

> testbsflist:=[test(x,y),q(x,y),`2DP2P1_gsq_bsf`];

> mkDirBC2(DBCueq,unknown_list,old_unknown_list, params_list,unkntestlist,testbsflist):

adddbc
SPdirb