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# BoundaryCondition Properties

Boundary condition for PDE model

A `BoundaryCondition` object specifies the type of PDE boundary condition on a set of geometry boundaries. A `PDEModel` object contains a vector of `BoundaryCondition` objects in its `BoundaryConditions` property.

Specify boundary conditions for your model using the `applyBoundaryCondition` function.

## Properties

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Boundary type, returned as `'dirichlet'`, `'neumann'`, or `'mixed'`.

Example: `applyBoundaryCondition(model,'dirichlet','Face',3,'u',0)`

Data Types: `char`

Geometric region type, returned as `'Face'` for 3-D geometry or `'Edge'` for 2-D geometry.

Example: `applyBoundaryCondition(model,'dirichlet','Face',3,'u',0)`

Data Types: `char` | `string`

Geometric region ID, returned as a vector of positive integers. Find the region IDs by using `pdegplot` with the `'FaceLabels'` (3-D) or `'EdgeLabels'` (2-D) value set to `'on'`.

Example: `applyBoundaryCondition(model,'dirichlet','Face',3:6,'u',0)`

Data Types: `double`

Dirichlet condition `h*u = r`, returned as a vector with N elements or a function handle. N is the number of PDEs in the system. For the syntax of the function handle form of `r`, see Nonconstant Boundary Conditions.

Example: `'r',[0;4;-1]`

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Dirichlet condition `h*u = r`, returned as an N-by-N matrix, a vector with N^2 elements, or a function handle. N is the number of PDEs in the system. For the syntax of the function handle form of `h`, see Nonconstant Boundary Conditions.

Example: `'h',[2,1;1,2]`

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Generalized Neumann condition `n·(c×````u) + qu = g```, returned as a vector with N elements or a function handle. N is the number of PDEs in the system. For scalar PDEs, the generalized Neumann condition is `n·(c````u) + qu = g```. For the syntax of the function handle form of `g`, see Nonconstant Boundary Conditions.

Example: `'g',[3;2;-1]`

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Generalized Neumann condition `n·(c×````u) + qu = g```, returned as an N-by-N matrix, a vector with N`^2` elements, or a function handle. N is the number of PDEs in the system. For the syntax of the function handle form of `q`, see Nonconstant Boundary Conditions.

Example: `'q',eye(3)`

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Dirichlet conditions, returned as a vector of up to N elements or as a function handle. If `u` has less than N elements, then you must also use `EquationIndex`. The `u` and `EquationIndex` arguments must have the same length. If `u` has N elements, then specifying `EquationIndex` is optional.

For the syntax of the function handle form of `u`, see Nonconstant Boundary Conditions.

Example: `applyBoundaryCondition(model,'dirichlet','Face',[2,4,11],'u',0)`

Data Types: `double`
Complex Number Support: Yes

Index of the known `u` components, returned as a vector of integers with entries from `1` to N. `EquationIndex` and `u` must have the same length.

Example: `applyBoundaryCondition(model,'mixed','Face',[2,4,11],'u',[3,-1],'EquationIndex',[2,3])`

Data Types: `double`

Vectorized function evaluation, returned as `'on'` or `'off'`. This evaluation applies when you pass a function handle as an argument. To save time in function handle evaluation, specify `'on'`, assuming that your function handle computes in a vectorized fashion. See Vectorization. For details of this evaluation, see Nonconstant Boundary Conditions.

Example: `applyBoundaryCondition(model,'dirichlet','Face',[2,4,11],'u',@ucalculator,'Vectorized','on')`

Data Types: `char`

## See Also

Introduced in R2015a

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