# mp-radiative-transport: Parameter description

## Contents

- [`base`](#base)
- [`time stepping`](#time-stepping)
- [`adaptive meshing`](#adaptive-meshing)
- [`rte`](#rte)
- [`laser`](#laser)
- [`output`](#output)
- [`profiling`](#profiling)

---

<a id="base"></a>
## `🔷 base`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `case name` | `string` | `not_initialized` | Sets the base name for the application that will be fed to the problem type. |
| `dimension` | `integer` | `2` | Defines the dimension of the problem |
| `number` | `string` | `double` | Floating point number format. Currently, only 'double' is explicitely instantiated.<br><br>Allowed values:<br>- `double` |
| `global refinements` | `integer` | `1` | Defines the number of initial global refinements |
| `do print parameters` | `boolean` | `True` | Set this parameter to true to list parameters in output |
| `verbosity level` | `integer` | `1` | Sets the verbosity level of the console output: 0: silent: for non-robust tests and benchmark runs; 1: minimal: for robust tests; 2: detailed; 3: full |
| [`fe`](#base-fe) | `object` |  | [See table](#base-fe) |

<a id="base-fe"></a>
### `base: fe`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `type` | `string` | `FE_Q` | Finite Element.FE_Q: hexahedral continuous finite element with polynomial degree p; FE_SimplexP: tetrahedral continuous finite element with polynomial degree p; FE_Q_iso_Q1: hexahedral continuous finite element with p subdivisions containing linear elements; FE_DGQ: hexahedral discontinuous finite element with polynomial degree p<br><br>Allowed values:<br>- `not_initialized`<br>- `FE_Q`<br>- `FE_SimplexP`<br>- `FE_Q_iso_Q1`<br>- `FE_DGQ` |
| `degree` | `integer` | `1` | Defines the degree p of the finite element type. If "type" is "FE_Q_iso_Q1" this parameter defines the number of subdivisions. |


---

<a id="time-stepping"></a>
## `🔷 time stepping`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `start time` | `number` | `0.0` | Defines the start time for the solution of the levelset problem |
| `end time` | `number` | `1.0` | Sets the end time for the solution of the levelset problem |
| `time step size` | `number` | `0.01` | Sets the step size for time stepping. For non-uniform time stepping, this parameter determines the size of the first time step. |
| `max n steps` | `integer` | `10000000` | Sets the maximum number of melt_pool steps |
| `time step size function` | `string` | `0.0*t` | Set an analytical function to determine the time step size. For the prediction of the new time increment, the old time is used. |


---

<a id="adaptive-meshing"></a>
## `🔷 adaptive meshing`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `do amr` | `boolean` | `False` | Set this parameter to true to activate adaptive meshing |
| `do not modify boundary cells` | `boolean` | `False` | Set this parameter to true to not refine/coarsen along boundaries. |
| `upper perc to refine` | `number` | `0.0` | Defines the (upper) percentage of elements that should be refined |
| `lower perc to coarsen` | `number` | `0.0` | Defines the (lower) percentage of elements that should be coarsened |
| `max grid refinement level` | `integer` | `12` | Defines the number of maximum refinement steps one grid cell will be undergone. |
| `min grid refinement level` | `integer` | `-1` | Defines the number of minimum refinement steps one grid cell will be undergone. |
| `n initial refinement cycles` | `integer` | `0` | Defines the number of initial refinements. |
| `every n step` | `integer` | `1` | Defines at every nth step the amr should be performed. |
| `min cells marked to refine` | `integer` | `1` | Minimum number of cells that must be marked for refinement/coarsening before the mesh is updated. |
| `min indicator threshold to refine cell` | `number` | `0.0` | Minimum indicator value required for a cell to be considered for refinement. |
| `solution transfer average values` | `boolean` | `False` | Set this parameter to true to average the contribututions to the same DoF coming from different cells during solution transfer. |


---

<a id="rte"></a>
## `🔷 rte`

| Parameter | Type | Default | Description |
|---|---|---|---|
| [`fe`](#rte-fe) | `object` |  | [See table](#rte-fe) |
| `rte verbosity level` | `integer` | `-1` | Sets the maximum verbosity level of the console output. The maximum level with respect to the  base value is decisive. |
| `predictor type` | `string` | `none` | Choose a predictor type.<br><br>Allowed values:<br>- `none`<br>- `pseudo_time_stepping` |
| `absorptivity type` | `string` | `gradient_based` | Chooses the formulation of the absorptivity coefficient<br><br>Allowed values:<br>- `constant`<br>- `gradient_based` |
| `avoid singular matrix absorptivity` | `number` | `1e-16` | Minimum value for absorptivity to ensure a non-singular matrix for RTE. |
| [`linear solver`](#rte-linear-solver) | `object` |  | [See table](#rte-linear-solver) |
| [`pseudo time stepping`](#rte-pseudo-time-stepping) | `object` |  | [See table](#rte-pseudo-time-stepping) |
| [`absorptivity`](#rte-absorptivity) | `object` |  | [See table](#rte-absorptivity) |

<a id="rte-fe"></a>
### `rte: fe`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `type` | `string` | `not_initialized` | Finite Element.FE_Q: hexahedral continuous finite element with polynomial degree p; FE_SimplexP: tetrahedral continuous finite element with polynomial degree p; FE_Q_iso_Q1: hexahedral continuous finite element with p subdivisions containing linear elements; FE_DGQ: hexahedral discontinuous finite element with polynomial degree p<br><br>Allowed values:<br>- `not_initialized`<br>- `FE_Q`<br>- `FE_SimplexP`<br>- `FE_Q_iso_Q1`<br>- `FE_DGQ` |
| `degree` | `integer` | `-1` | Defines the degree p of the finite element type. If "type" is "FE_Q_iso_Q1" this parameter defines the number of subdivisions. |

<a id="rte-linear-solver"></a>
### `rte: linear solver`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `solver type` | `string` | `GMRES` | Set this parameter for choosing an iterative linear solver type.<br><br>Allowed values:<br>- `CG`<br>- `GMRES` |
| `preconditioner type` | `string` | `ILU` | Set this parameter for choosing a preconditioner type.<br><br>Allowed values:<br>- `Identity`<br>- `AMG`<br>- `ILU`<br>- `Diagonal` |
| `max iterations` | `integer` | `10000` | Set the maximum number of iterations for solving the linear system of equations. |
| `rel tolerance` | `number` | `1e-12` | Set the relative tolerance for a successful solution of the linear system of equations. |
| `abs tolerance` | `number` | `1e-20` | Set the absolute tolerance for a successful solution of the linear system of equations. |
| `do matrix free` | `boolean` | `True` | Set this parameter if a matrix free solution procedure should be performed. |
| `monitor type` | `string` | `none` | Set the monitor type of the linear solver.<br><br>Allowed values:<br>- `none`<br>- `reduced`<br>- `all` |

<a id="rte-pseudo-time-stepping"></a>
### `rte: pseudo time stepping`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `diffusion term scaling` | `number` | `1.0` | Scaling parameter of diffusion term. |
| `advection term scaling` | `number` | `1.0` | Scaling parameter of advection term. |
| `pseudo time scaling` | `number` | `0.01` | Determine the pseudo-time step as the product of this scaling and minimum cell size. |
| `rel tolerance` | `number` | `0.001` | Pseudo-time stepping relative tolerance. |
| [`time stepping`](#rte-pseudo-time-stepping-time-stepping) | `object` |  | [See table](#rte-pseudo-time-stepping-time-stepping) |
| [`linear solver`](#rte-pseudo-time-stepping-linear-solver) | `object` |  | [See table](#rte-pseudo-time-stepping-linear-solver) |

<a id="rte-pseudo-time-stepping-time-stepping"></a>
#### `rte: pseudo time stepping: time stepping`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `start time` | `number` | `0.0` | Defines the start time for the solution of the levelset problem |
| `end time` | `number` | `1.79769e+308` | Sets the end time for the solution of the levelset problem |
| `time step size` | `number` | `0.0` | Sets the step size for time stepping. For non-uniform time stepping, this parameter determines the size of the first time step. |
| `max n steps` | `integer` | `1` | Sets the maximum number of melt_pool steps |
| `time step size function` | `string` | `0.0*t` | Set an analytical function to determine the time step size. For the prediction of the new time increment, the old time is used. |

<a id="rte-pseudo-time-stepping-linear-solver"></a>
#### `rte: pseudo time stepping: linear solver`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `solver type` | `string` | `CG` | Set this parameter for choosing an iterative linear solver type.<br><br>Allowed values:<br>- `CG`<br>- `GMRES` |
| `preconditioner type` | `string` | `ILU` | Set this parameter for choosing a preconditioner type.<br><br>Allowed values:<br>- `Identity`<br>- `AMG`<br>- `ILU`<br>- `Diagonal` |
| `max iterations` | `integer` | `10000` | Set the maximum number of iterations for solving the linear system of equations. |
| `rel tolerance` | `number` | `1e-12` | Set the relative tolerance for a successful solution of the linear system of equations. |
| `abs tolerance` | `number` | `1e-20` | Set the absolute tolerance for a successful solution of the linear system of equations. |
| `do matrix free` | `boolean` | `True` | Set this parameter if a matrix free solution procedure should be performed. |
| `monitor type` | `string` | `none` | Set the monitor type of the linear solver.<br><br>Allowed values:<br>- `none`<br>- `reduced`<br>- `all` |

<a id="rte-absorptivity"></a>
### `rte: absorptivity`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `absorptivity gas` | `number` | `0.1` | Sets the absorptivity of the gas phase. |
| `absorptivity liquid` | `number` | `0.9` | Sets the absorptivity of the liquid phase. |
| `avoid div zero constant` | `number` | `1e-16` | Sets the absorptivity of the gas phase. |


---

<a id="laser"></a>
## `🔷 laser`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `model` | `string` | `not_initialized` | Laser model. analytical_temperature: see Mirkoohi et al. (2019); volumetric: volumetric heat source, the intensity is defined by ""intensity profile""; interface_projection: projection-based regularized continuum surface flux in "direction", the intensity is defined by ""intensity profile""; interface_projection_sharp: projection-based sharp surface flux in "direction", the intensity is defined by ""intensity profile""; interface_projection_sharp_conforming: projection-based sharp surface flux in "direction" on a conforming mesh, the intensity is defined by ""intensity profile""; RTE: continuum surface flux projected using the radiative transport equation in "direction", supporting shadowing of undercuts, the intensity is defined by ""intensity profile"";<br><br>Allowed values:<br>- `not_initialized`<br>- `analytical_temperature`<br>- `volumetric`<br>- `interface_projection_regularized`<br>- `interface_projection_sharp`<br>- `interface_projection_sharp_conforming`<br>- `RTE` |
| `intensity profile` | `string` | `Gauss` | Laser intensity profile. uniform: note that the "power" input is treated as the uniform power density in the whole domain; Gauss: Gaussian laser intensity shape with "radius" that retains the "power"; Gusarov: see Gusarov et al. (2009);<br><br>Allowed values:<br>- `uniform`<br>- `Gauss`<br>- `Gusarov` |
| `power` | `number` | `0.0` | Laser power |
| `power over time` | `string` | `constant` | Temporal distribution of the laser power<br><br>Allowed values:<br>- `constant`<br>- `ramp` |
| `power start time` | `number` | `0.0` | In case of time-dependent laser power: activation time of |
| `power end time` | `number` | `1.79769e+308` | In case of time-dependent laser power: end time of |
| `absorptivity gas` | `number` | `1.0` | Laser energy absorptivity of the gaseous part of the domain. |
| `absorptivity liquid` | `number` | `1.0` | Laser energy absorptivity of the liquid part of the domain. |
| `starting position` | `string` | `` | Center coordinates of the laser beam starting position on the interface melt/gas. |
| `scan speed` | `number` | `0.0` | Scan speed of the laser |
| `scan direction` | `string` | `` | Direction of laser motion as a vector |
| `beam direction` | `string` | `` | Laser beam direction. |
| `beam rotation axis` | `string` | `` | Axis around which the initial laser beam direction will be rotated. Relevant only in 3D. |
| `beam rotation angle` | `number` | `0.0` | Rotation angle applied to the laser beam direction (in 3D about 'beam rotation axis' following the right-hand rule; in 2D: as defined by the 2D rotation matrix |
| `radius` | `number` | `0.0` | Laser beam radius. |
| [`gusarov`](#laser-gusarov) | `object` |  | [See table](#laser-gusarov) |
| [`analytical`](#laser-analytical) | `object` |  | [See table](#laser-analytical) |
| [`dirac delta function approximation`](#laser-dirac-delta-function-approximation) | `object` |  | [See table](#laser-dirac-delta-function-approximation) |

<a id="laser-gusarov"></a>
### `laser: gusarov`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `reflectivity` | `number` | `0.0` | Reflectivity of the material. |
| `extinction coefficient` | `number` | `0.0` | Extinction coefficient in [1/m]. |
| `layer thickness` | `number` | `0.0` | Layer thickness |

<a id="laser-analytical"></a>
### `laser: analytical`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `ambient temperature` | `number` | `0.0` | Ambient temperature in the inert gas. |
| `max temperature` | `number` | `0.0` | Maximum temperature arising in the melt pool. If this temperature is lower than the boiling temperature, this value is corrected to correspond to the boiling temperature + 500 K. |
| `temperature x to y ratio` | `number` | `1.0` | This factor scales the analytical temperature field to be anisotropic. |

<a id="laser-dirac-delta-function-approximation"></a>
### `laser: dirac delta function approximation`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `type` | `string` | `norm_of_indicator_gradient` | Choose how to smear a parameter over the interface.<br><br>Allowed values:<br>- `norm_of_indicator_gradient`<br>- `heaviside_phase_weighted`<br>- `heaviside_times_heaviside_phase_weighted`<br>- `reciprocal_phase_weighted`<br>- `reciprocal_times_heaviside_phase_weighted`<br>- `heavy_phase_only` |
| `auto weights` | `boolean` | `False` | Choose if weights should be computed automatically. |
| `gas phase weight` | `number` | `1.0` | If >>> dirac delta function approximation type <<< is set to any phase weighted optionthis parameter controls the (first) weight of the gas phase (level set = -1). |
| `heavy phase weight` | `number` | `1.0` | If >>> dirac delta function approximation type <<< is set to any phase weighted optionthis parameter controls the (first) weight of the heavy phase (level set = 1). |
| `gas phase weight 2` | `number` | `1.0` | If >>> dirac delta function approximation type <<< is set to >>> heaviside_times_heaviside_phase_weighted <<< this parameter controls the second weight of the gas phase (level set = -1). |
| `heavy phase weight 2` | `number` | `1.0` | If >>> dirac delta function approximation type <<< is set to >>> heaviside_times_heaviside_phase_weighted <<< this parameter controls the second weight of the heavy liquid/solid phase (level set = 1). |


---

<a id="output"></a>
## `🔷 output`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `directory` | `string` | `./` | Sets the base directory for all output. |
| `write frequency` | `integer` | `1` | Every n timestep that should be written |
| `write time step size` | `number` | `1.79769e+308` | Write output output every given time step. If this parameter is set, the output write frequency is deactivated. |
| `output variables` | `string` | `all` | Specify variables that you request to output. |
| `do user defined postprocessing` | `boolean` | `False` | Set this parameter to true to enable user defined postprocessing. |
| [`paraview`](#output-paraview) | `object` |  | [See table](#output-paraview) |
| [`particles`](#output-particles) | `object` |  | [See table](#output-particles) |

<a id="output-paraview"></a>
### `output: paraview`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `enable` | `boolean` | `False` | Set this parameter to true to activate paraview output. |
| `filename` | `string` | `solution` | Sets the base name for paraview output files. |
| `n digits timestep` | `integer` | `4` | Number of digits for the frame number of the vtu-file. |
| `print boundary id` | `boolean` | `False` | Set this parameter to true to output a vtu-file with the boundary id. |
| `output subdomains` | `boolean` | `False` | Set this parameter to true to output the subdomain ranks. |
| `output material id` | `boolean` | `False` | Set to true to output the material id. |
| `write higher order cells` | `boolean` | `True` | Set this parameter to false to write bi- or trilinear data only. Set this parameter to true to write higher order cell data. Note: higher order cell data can only be written for hexahedron meshes and 2 or 3 dimensions. |
| `n groups` | `integer` | `1` | Number of parallel written vtu-files. |
| `n patches` | `integer` | `0` | Control number of patches to enable high-order. |

<a id="output-particles"></a>
### `output: particles`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `enable` | `boolean` | `False` | Set this parameter to true to activate particle paraview output. |
| `filename` | `string` | `particle` | Sets the base name for particle output files. |


---

<a id="profiling"></a>
## `🔷 profiling`

| Parameter | Type | Default | Description |
|---|---|---|---|
| `enable` | `boolean` | `False` | Set this parameter to true if profiling should be enabled. It will be automaticallyenabled for verbosity level >=1. |
| `write time step size` | `number` | `10.0` | Write profiling output every given time step size. If this parameter is set, the specified parameter for write frequency is overwritten. |
| `time type` | `string` | `real` | Choose the type of time measure to write profiling information.<br><br>Allowed values:<br>- `real`<br>- `simulation` |


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