petsc-main 2021-04-20
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Add a boundary condition to the model. The pointwise functions are used to provide boundary values for essential boundary conditions. In FEM, they are acting upon by dual basis functionals to generate FEM coefficients which are fixed. Natural boundary conditions signal to PETSc that boundary integrals should be performaed, using the kernels from PetscDSSetBdResidual().


#include "petscds.h" 
PetscErrorCode PetscDSAddBoundaryByName(PetscDS ds, DMBoundaryConditionType type, const char name[], const char lname[], PetscInt Nv, const PetscInt values[], PetscInt field, PetscInt Nc, const PetscInt comps[], void (*bcFunc)(void), void (*bcFunc_t)(void), void *ctx, PetscInt *bd)
Collective on ds

Input Parameters

ds - The PetscDS object
type - The type of condition, e.g. DM_BC_ESSENTIAL/DM_BC_ESSENTIAL_FIELD (Dirichlet), or DM_BC_NATURAL (Neumann)
name - The BC name
lname - The naem of the label defining constrained points
Nv - The number of DMLabel values for constrained points
values - An array of label values for constrained points
field - The field to constrain
Nc - The number of constrained field components (0 will constrain all fields)
comps - An array of constrained component numbers
bcFunc - A pointwise function giving boundary values
bcFunc_t - A pointwise function giving the time derviative of the boundary values, or NULL
ctx - An optional user context for bcFunc

Output Parameters

bd - The boundary number

Options Database Keys

-bc_<boundary name> <num> - Overrides the boundary ids
-bc_<boundary name>_comp <num> - Overrides the boundary components


This function should only be used with DMForest currently, since labels cannot be defined before the underlygin Plex is built.

Both bcFunc abd bcFunc_t will depend on the boundary condition type. If the type if DM_BC_ESSENTIAL, Then the calling sequence is

bcFunc(PetscInt dim, PetscReal time, const PetscReal x[], PetscInt Nc, PetscScalar bcval[])

If the type is DM_BC_ESSENTIAL_FIELD or other _FIELD value, then the calling sequence is

bcFunc(PetscInt dim, PetscInt Nf, PetscInt NfAux,
       const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
       const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
       PetscReal time, const PetscReal x[], PetscScalar bcval[])

dim - the spatial dimension
Nf - the number of fields
uOff - the offset into u[] and u_t[] for each field
uOff_x - the offset into u_x[] for each field
u - each field evaluated at the current point
u_t - the time derivative of each field evaluated at the current point
u_x - the gradient of each field evaluated at the current point
aOff - the offset into a[] and a_t[] for each auxiliary field
aOff_x - the offset into a_x[] for each auxiliary field
a - each auxiliary field evaluated at the current point
a_t - the time derivative of each auxiliary field evaluated at the current point
a_x - the gradient of auxiliary each field evaluated at the current point
t - current time
x - coordinates of the current point
numConstants - number of constant parameters
constants - constant parameters
bcval - output values at the current point

See Also

PetscDSAddBoundary(), PetscDSGetBoundary(), PetscDSSetResidual(), PetscDSSetBdResidual()







Index of all DT routines
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Index of all manual pages