mod_explicit_add_cell_bc Module Reference

Fill ghost nodes with given boundary conditions for cell scalars.

Functions/Subroutines
subroutine	explicit_add_cell_bc (scalar, boundary_condition)
	Compute the equivalent Dirichlet boundary value of a field and store the result in the first ghost cell in each direction.

Function/Subroutine Documentation

explicit_add_cell_bc()

subroutine mod_explicit_add_cell_bc::explicit_add_cell_bc	(	double precision, dimension(:,:,:), intent(inout)	scalar,
		type(t_boundary_condition), intent(in)	boundary_condition )

The computation is done for Neumann boundaries.

• The Neumann value is modified as to account for the wanted extrapolated derivative at the destination cells *.

This is done by applying a different Neumann condition which is the extrapolation of the derivative at the extrapolated point (order 2):

\[ \phi(\alpha) \simeq \phi(x_0) + \alpha D^1(x_0) + \alpha^2/2 D^2(x_0) \Rightarrow \frac{d \phi}{d x}(\alpha) \simeq D^1(x_0) + \alpha D^2(x_0) \Rightarrow D^1(x_0) \simeq \frac{d \phi}{d x}(\alpha) - \alpha D^2(x_0) \]

where \( \alpha \) is the distance between the extrapolation cell and the place where the derivative is given.

Example

if the right face is a Neumann boundary, then scalar(i,je+1,k) will be filled with the 2nd order extrapolated value at the cell (not the face!).

Note

For Dirichlet boundaries, the value is simply copied.

Parameters

[in,out]	scalar	scalar field
[in]	boundary_condition	boundary conditions.

Todo

MCO: do better extrapolation (not sequential)