B Utilities

Modules
	Groupsets
	lbs.BoundaryOptionsBlock
	lbs.OptionsBlock

Detailed Description

Boundary Conditions

LBS supports the boundary condition "incident_anisotropic_heterogeneous", which allows for a very intricate type of boundary condition to be specified.For example, consider the boundary condition applied to boundary zmax below:

chiLBSSetOptions(phys1,
{
  spatial_discretization = "pwld",
  scattering_order = 2,
  boundary_conditions =
  {
    { name = "zmax", type = "incident_anisotropic_heterogeneous",
      function_name = "luaBoundaryFunctionA"},
  }
})

It points to the lua function "luaBoundaryFunctionA". This lua function will be called with the following parameters:

size_t        cell_global_id,
int           cell_material_id,
unsigned int  face_index,
unsigned int  face_node_index,
const chi_mesh::Vector3& face_node_location,
const chi_mesh::Vector3& face_node_normal,
const std::vector<int>& quadrature_angle_indices,
const std::vector<chi_mesh::Vector3>& quadrature_angle_vectors,
const std::vector<std::pair<double,double>>& quadrature_phi_theta_angles,
const std::vector<int>& group_indices,
double evaluation_time;

and must return a 1D array of data-values ordered first by angle index, then by group index, e.g., n0g0, n0g1, n0g2, n1g0, n1g1, n1g2, etc.Example lua function:

function luaBoundaryFunctionA(cell_global_id,
                              material_id,
                              location,
                              normal,
                              quadrature_angle_indices,
                              quadrature_angle_vectors,
                              quadrature_phi_theta_angles,
                              group_indices)
    num_angles = rawlen(quadrature_angle_vectors)
    num_groups = rawlen(group_indices)
    psi = {}
    dof_count = 0
 
    for ni=1,num_angles do
        omega = quadrature_angle_vectors[ni]
        phi_theta = quadrature_phi_theta_angles[ni]
        for gi=1,num_groups do
            g = group_indices[gi]
 
            value = 1.0
 
            dof_count = dof_count + 1
            psi[dof_count] = value
        end
    end
 
    return psi
end

An example of a very intricate use of this functionality can be seen in the test tests_Transport_Steady_Transport2D_5PolyA_AniHeteroBndry_lua

Field Functions

LBS solvers create a number of field functions. Here is the logic for it:

• Field functions are by default named phi_gXXX_mYYY where XXX is a zero padded 3 digit number for the group number. YYY is a zero padded 3 digit number for the moment number. Numbers spanning beyond the 3 digits will have no zero padding and will be represented normally (the 3 digit padding just helps in visualization cases). Example: Suppose this is a 3D simulation, 2 groups, scattering order of 1 (resulting in 4 moments)

  phys1 = chiLBSCreateSolver()
  chiSolverAddRegion(phys1,region1)
  --
  -- Add Groupset construction here
  --
  chiLBSSetProperty(phys1,DISCRETIZATION_METHOD,PWLD)
  chiLBSSetProperty(phys1,SCATTERING_ORDER,1)
  --
  chiLBSInitialize(phys1)
  chiLBSExecute(phys1)
  --
  fflist,count = chiLBSGetScalarFieldFunctionList(phys1)

will create field functions

phi_g000_m000
phi_g000_m001
phi_g000_m002
phi_g000_m003
phi_g001_m000
phi_g001_m001
phi_g001_m002
phi_g001_m003

We can get the scalar field functions with a call to chiLBSGetScalarFieldFunctionList which will return a table with the field function handles of only the scalar fields. E.g.,

fflist = chiLBSGetScalarFieldFunctionList(phys1)

with fflist containing handles to

phi_g000_m000
phi_g001_m000

Additionally, LBS can create a power generation field function with the default name power_generation.

chiLBSSetOptions(phys1,
{
  spatial_discretization = "pwld",
  scattering_order = 2,
  power_field_function_on = true,
  power_default_kappa = 1.0,
  power_normalization = -1.0, --Negative means its disabled
})

All of the field function can be supplied with a prefix, either using the solver name

chiLBSSetOptions(phys1,
{
  spatial_discretization = "pwld",
  scattering_order = 2,
  power_field_function_on = true,
  power_default_kappa = 1.0,
  power_normalization = -1.0, --Negative means its disabled
 
  field_function_prefix_option = "solver_name"
})

or by setting a different prefix

chiLBSSetOptions(phys1,
{
  spatial_discretization = "pwld",
  scattering_order = 2,
  power_field_function_on = true,
  power_default_kappa = 1.0,
  power_normalization = -1.0, --Negative means its disabled
 
  field_function_prefix = "prefixx"
})