Boundary conditions.
For each boundary label found in the mesh, there needs to be a definition of the boundary condition to apply at the corresponding faces. What kind of boundary conditions are available depends on the equation system, but each boundary condition needs to be identified by a label, that matches the one defined in the mesh.
If there are values that are to be extrapolated (Neumann boundary
condition), you can set enforce_zero_grad to true, to use an extrapolation
of a polynomial with zero gradient at the boundary.
This is achieved by computing the last mode to fulfill this condition.
If you set neumann_mode_fraction to a smaller value than 1, then only
this fraction of lower modes will be used in the enforce_zero_grad
procedure and higher modes will be set to 0.
Simple example with two different boundary conditions, one without further options (slipwall) and one with further settings (inflow):
boundary condition = {
{ -- SLIPWALL
-- Velocity in normal direction 0, other values extrapolated.
label = 'cylinder',
kind = 'slipwall', -- or 'wall'
enforce_zero_grad = true,
neumann_mode_fraction = 1.0
},
{ -- INFLOW
-- Prescribe density and velocity, extrapolate pressure.
label = 'outside',
kind = 'conservatives',
density = 1.23,
velocityX = 0.2,
velocityY = 0.3,
velocityZ = 0.4
enforce_zero_grad = true,
neumann_mode_fraction = 1.0
}
}
If there is a boundary in the mesh, for which no boundary condition is defined the application will stop. Boundary conditions that are defined, but for which there is no label in the mesh, will be ignored.
This type describes a single boundary condition, which is described in the configuration files and attached to elements in the mesh file.
| Type | Visibility | Attributes | Name | Initial | |||
|---|---|---|---|---|---|---|---|
| character(len=LabelLen), | public | :: | label |
A label identifying this boundary condition |
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| character(len=LabelLen), | public | :: | BC_kind |
The kind of this boundary condition, mainly used to describe predefined boundary conditions with some default settings for some of the variables. |
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| logical, | public | :: | enforce_zero_grad |
Method to use for the extrapolation of Neumann boundaries. |
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| real(kind=rk), | public | :: | neumann_mode_fraction |
Fraction of modes to use for the extrapolation to obtain Neumann BCs. |
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| logical, | public | :: | bc_normal_vec |
A flag to indicate if vectorial quantities are defined in the boundary normal system. |
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| type(tem_bc_state_type), | public, | allocatable | :: | state(:) |
Boundary condition description for each of the state variables. The size of this array depends on the equation system and covers all required variables. The variables are expected to occur in the same order as in the equation system. Furthermore, in case of face normal boundary conditions, we assume that the variable normal to the face is occurring first in this array. |
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| type(grw_stringkeyvaluepairarray_type), | public | :: | varDict |
Dictionary of boundary state variable with varDict%val()%key is the name of boundary variable and varDict%val()%value is the name of spacetime function variable |
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| type(atl_eqn_var_trafo_type), | public | :: | bc_trafo |
Pointer to function for the necessary state variable transformation. |
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| logical, | public | :: | bc_normal_vec_gradient |
A flag to indicate if derivatives of vectorial quantities are defined in the boundary normal system. |
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| type(atl_eqn_var_trafo_type), | public | :: | bc_trafo_gradient |
Pointer to function for the necessary state gradient variable transformation. |
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| type(tem_bc_state_type), | public, | allocatable | :: | state_gradient(:) |
Boundary condition description for each of higher order terms of the equations. |
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| type(grw_stringkeyvaluepairarray_type), | public | :: | varDict_gradient |
Dictionary of boundary state gradient variable with varDict%val()%key is the name of boundary variable and varDict%val()%value is the name of spacetime function variable. |
Get the boundary configuration.
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| type(atl_boundary_type), | intent(out), | allocatable | :: | bc(:) |
Array of boundary conditions, will be allocated in this routine and has a length according to the number of boundary conditions in the mesh. |
|
| type(tem_bc_header_type), | intent(out) | :: | bc_header |
The boundary condition header data as given in the mesh. |
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| type(tem_BC_prop_type), | intent(in) | :: | bc_prop |
The boundary property object, describing the given boundaries in the mesh, this has to be provided to allow the matching of boundary settings in the configuration to the boundary set in the mesh. |
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| type(atl_Equations_type), | intent(inout) | :: | equation |
Description of the equation system, to read the boundary conditions in dependency on the equation system to solve. |
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| type(flu_State) | :: | conf |
Lua script to obtain the configuration data from. |
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| integer, | intent(in), | optional | :: | parent |
A parent Lua table, in which the boundary conditions are to be found. |
Routine to store position of user variable defined state and state_gradient boundary variable in bc(iBC)%state(iVar)%varPos and bc(iBC)%state_gradient
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| type(atl_boundary_type), | intent(inout) | :: | bc(:) |
Array of boundary conditions contains varDict with same size as state variables |
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| type(tem_varSys_type), | intent(in) | :: | varSys |
Global variable system |