# 7.26. Enclosure Radiation

This section is referenced in the following other sections

- Releases & Deprecations: Version 5.18 (2024/02/23)
- Simulation Setup: Enclosure Radiation

## 7.26.1. Viewfactor Calculation

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  This block command specifies a radiation enclosure and is used to define a method for calculating view factors. The parameter for this block corresponds to an instance of a radiation enclosure mechanics.

    begin Viewfactor Calculation Vf_calc

       Bsp Tree Max Depth {=} depth And Min List Length {=} l

       Compute Rule {=} {hemicube | pairwise | read}

       Enclosure Quality Error Tolerance {=} Tolerance

       Enclosure Quality Warning Tolerance {=} Tolerance

       Geometric Tolerance {=} n

       Hemicube Max Subdivides {=} n

       Hemicube Min Separation {=} n

       Hemicube Resolution {=} n

       Number Of Rotations {=} n

       Output Rule {=} {more verbose | none | summary | verbose}

       Pairwise Monte Carlo Sample Rule {=} {halton | jitter | random | uniform}

       Pairwise Monte Carlo Tol1 {=} Real_value

       Pairwise Monte Carlo Tol2 {=} Real_value

       Pairwise Number Of Monte Carlo Samples {=} n

       Pairwise Number Of Visibility Samples {=} n

       Pairwise Visibility Sample Rule {=} {halton | jitter | random | uniform}

       X-Y Plane Symmetry

       X-Z Plane Symmetry

       Y-Z Plane Symmetry

    end Viewfactor Calculation Vf_calc

### 7.26.1.1. Line Commands

###### Bsp Tree Max Depth

Syntax

  Bsp Tree Max Depth {=} depth And Min List Length {=} l

Summary

  This line command sets the BSP tree parameters.

Description

  This line command sets the parameters for the Binary Space Partitioning (BSP) tree. This data structure is used to accelerate the geometric operations associated with visibility to calculate the view factors. The maximum depth of the tree will set the maximum number of partitioning boxes created for a given enclosure. The minimum list length will set the desired number faces to be contained in a box. The depth of the tree will be increased until the minimum list length is met of the maximum depth is reached. It is suggested that these parameters not be adjusted from their default values.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
depth | integer | 12
{=} | {= | are | is} | –
l | integer | 25

###### Compute Rule

Syntax

  Compute Rule {=} {hemicube | pairwise | read}

Summary

  This line command sets the method for computing the view factors for this enclosure.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
VFComputeRule | {hemicube | pairwise | read} | HEMICUBE

###### Enclosure Quality Error Tolerance

Syntax

  Enclosure Quality Error Tolerance {=} Tolerance

Summary

  A viewfactor quality tolerance before an error is thrown

Description

  A tolerance on enclosure quality defined as the area-weighted Linf of the raw rowsum minus 1 for the enclosures. If an enclosure is detected with a rowsum error larger than this tolerance an error is thrown and a list of the offending enclosures is printed to the aria log file. The default for this parameter is 0.05

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Tolerance | real | –

###### Enclosure Quality Warning Tolerance

Syntax

  Enclosure Quality Warning Tolerance {=} Tolerance

Summary

  A viewfactor quality tolerance before warnings are issued

Description

  A tolerance on enclosure quality defined as the area-weighted Linf of the raw rowsum minus 1 for the enclosures. If an enclosure is detected with a rowsum error larger than this tolerance a warning message is printed in the aria log file along with a list of the offending enclosures. The default for this parameter is 1e-3

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Tolerance | real | 1.0e-3

###### Geometric Tolerance

Syntax

  Geometric Tolerance {=} n

Summary

  Set the geometric tolerance

Description

  This line command sets the spatial geometry tolerance for use in all geometry-related comparisons. This value should correspond to the known minimum geometric size of the element faces used to define the enclosure.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | real | 1.0e-6

###### Hemicube Max Subdivides

Syntax

  Hemicube Max Subdivides {=} n

Summary

  Set the upper limit of hemicube subdivides

Description

  This line command sets the upper limit of the number of element-face subdivides that will occur when the proximity criteria limit is exceeded (see the HEMICUBE MIN SEPARATION line command).

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | integer | 2

###### Hemicube Min Separation

Syntax

  Hemicube Min Separation {=} n

Summary

  Set the hemicube minimum separation

Description

  This line command sets a non-dimensional minimum-separation distance allowed between element faces for the HEMICUBE method before the face is subdivided. The accuracy of the hemicube method degrades rapidly if the element faces are in close proximity to each other. This tolerance is based on dividing the normal distance between the center of the element faces by the effective diameter of the element face.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | real | 5

###### Hemicube Resolution

Syntax

  Hemicube Resolution {=} n

Summary

  Set the hemicube resolution

Description

  This line command sets the number of uniform sub-patches into which the hemicube will be divided.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | integer | 400

###### Number Of Rotations

Syntax

  Number Of Rotations {=} n

Summary

  For an enclosure boundary defined with 2D axisymmetric geometry ONLY. Set the number of incremental segment rotations to define a 3D enclosure surface. Rotations are swept over 360 degrees for COMPUTE RULE Hemicube and over 180 degrees for COMPUTE RULE Pairwise.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | integer | 1

###### Output Rule

Syntax

  Output Rule {=} {more verbose | none | summary | verbose}

Summary

  Selects the amount of information printed describing the view factor calculation

Description

  By default a summary of the input values are output. The MORE VERBOSE option will print both the summary information and progress of the view factor calculation in percent done. The percent done is useful in estimating how much runtime should be allotted for the calculation.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
OutputRule | {more verbose | none | summary | verbose} | SUMMARY

###### Pairwise Monte Carlo Sample Rule

Syntax

  Pairwise Monte Carlo Sample Rule {=} {halton | jitter | random | uniform}

Description

  This line command selects the method for the distribution of Monte Carlo integration sample points on the surface for view-factor quadrature.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
AMCSampleRule | {halton | jitter | random | uniform} | HALTON

###### Pairwise Monte Carlo Tol1

Syntax

  Pairwise Monte Carlo Tol1 {=} Real_value

Summary

  Set first of two convergence checks for Monte Carlo integration

Description

  This line command sets one of the two convergence checks used by the Monte Carlo integration algorithm for the PAIRWISE method. If the standard deviation of the view factor divided by the value of the view factor is less than this tolerance, the Monte Carlo integration will terminate i.e

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Real_value | real | 1.0e-5

###### Pairwise Monte Carlo Tol2

Syntax

  Pairwise Monte Carlo Tol2 {=} Real_value

Summary

  Set second of two convergence checks for Monte Carlo integration

Description

  This line command sets one of the two convergence checks used by the Monte Carlo integration algorithm for the PAIRWISE method. If the standard deviation of the view factor is less than this tolerance, the Monte Carlo integration will terminate i.e

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Real_value | real | 1.0e-5

###### Pairwise Number Of Monte Carlo Samples

Syntax

  Pairwise Number Of Monte Carlo Samples {=} n

Summary

  Set the pairwise number of Monte Carlo sample points

Description

  This line command specifies the number of Monte Carlo integration sample points when Monte Carlo integration is activated during the PAIRWISE view-factor-calculation algorithm.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | integer | 1000

###### Pairwise Number Of Visibility Samples

Syntax

  Pairwise Number Of Visibility Samples {=} n

Summary

  Set the pairwise number visibility sample points

Description

  This line command will set the number of sample points to use for evaluating visibility between element faces for the PAIRWISE view-factor-calculation algorithm. Visibility is used to select the method for calculating the view factors. If the two element faces are completely visible to each other, the view factor is calculated using Gauss quadrature or an analytic method. If the element faces are partially visible, Monte Carlo integration is used.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | integer | 25

###### Pairwise Visibility Sample Rule

Syntax

  Pairwise Visibility Sample Rule {=} {halton | jitter | random | uniform}

Summary

  Set the pairwise visibility sample rule

Description

  This line command selects the method for distributing the visibility sample points on the surface.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
AVSampleRule | {halton | jitter | random | uniform} | UNIFORM

###### X-Y Plane Symmetry

Syntax

  X-Y Plane Symmetry

Summary

  Specifies symmetry about the X-Y plane.

###### X-Z Plane Symmetry

Syntax

  X-Z Plane Symmetry

Summary

  Specifies symmetry about the X-Z plane.

###### Y-Z Plane Symmetry

Syntax

  Y-Z Plane Symmetry

Summary

  Specifies symmetry about the Y-Z plane.

## 7.26.2. Viewfactor Smoothing

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  Defines a view factor smoothing scheme and its associated parameters.

Description

  This block command is used to define a method for smoothing the view factors. The defined method will be used for view factor smoothing only when requested with the USE VIEWFACTOR SMOOTHING line command in the ENCLOSURE DEFINITION command block.

  When VIEWFACTOR SMOOTHING is requested a two step sequence is initiated

  1. Reciprocity enforcement using the specified RECIPROCITY RULE

  2. Rowsum enforcement as per the specified METHOD

  In both steps the viewfactor matrix will be modified as prescribed.

  Note

  In step 1 the appropriate modifications are always applied. However, if the rowsum enforcement criteria of step 2 are not satisfied the viewfactor matrix supplied to the enclosure radiation calculation will be the viewfactor matrix resulting from step 1 and -not- the raw viewfactor matrix.

    begin Viewfactor Smoothing Vf_smooth

       Convergence Tolerance {=} Param1

       Maximum Iterations {=} n

       Method {=} {least-squares | none | simple}

       Output Rule {=} {more verbose | none | summary | verbose}

       Reciprocity Rule {=} {addition | average | none | subtraction}

       Weight Power {=} Param1

    end Viewfactor Smoothing Vf_smooth

### 7.26.2.1. Line Commands

###### Convergence Tolerance

Syntax

  Convergence Tolerance {=} Param1

Summary

  Sets convergence tolerance.

Description

  This line command sets the convergence tolerance for both the SIMPLE and LEAST-SQUARES smoothing algorithms based on the following:

  1) SIMPLE: 2) LEAST-SQUARES:

  where r is the residual of the Lagrange multiplier matrix problem.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Param1 | real | 1.0e-8

###### Maximum Iterations

Syntax

  Maximum Iterations {=} n

Summary

  Set maximum iterations.

Description

  This line command sets the maximum number of iterations that the SIMPLE smoothing algorithm will take.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
n | integer | 500

###### Method

Syntax

  Method {=} {least-squares | none | simple}

Summary

  Defines view factor smoothing method.

Description

  This line command defines the algorithm for smoothing the view factors. Smoothing is a term used to describe the process of enforcing the row-sum property of the view-factor matrix given by

  and the reciprocity property of view factors given by

  The HEMICUBE method guarantees the row-sum property, but not necessarily the reciprocity property. The PAIRWISE method will guarantee the reciprocity property (lower diagonal is calculated and the upper triangular is filled in using reciprocity), but not necessarily the row-sum property. If these two properties are not met by the view-factor matrix, energy conservation will not be achieved.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
VFSmoothMethod | {least-squares | none | simple} | LEAST-SQUARES

###### Output Rule

Syntax

  Output Rule {=} {more verbose | none | summary | verbose}

Summary

  Set the amount of output.

Description

  This line command sets the amount of information reported to the output screen about the view-factor smoothing.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
OutputRule | {more verbose | none | summary | verbose} | SUMMARY

###### Reciprocity Rule

Syntax

  Reciprocity Rule {=} {addition | average | none | subtraction}

Summary

  Selects reciprocity enforcement rule.

Description

  This line command determines the method for enforcing reciprocity,

  during smoothing. This command is only required for the HEMICUBE algorithm. The PAIRWISE algorithm uses reciprocity to fill in the lower triangular part of the view-factor matrix. If both of the view factors, and , are nonzero, these factors are adjusted by averaging and .

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
VFMatrixSymmRule | {addition | average | none | subtraction} | AVERAGE

###### Weight Power

Syntax

  Weight Power {=} Param1

Summary

  Sets weight power.

Description

  This line command sets the power, , used for the weights in the LEAST-SQUARES smoothing algorithm

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Param1 | real | 2.0

## 7.26.3. Radiosity Solver

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  Defines a radiosity solver to be used by the enclosure definition.

Description

  This block command contains methods associated with the solution of the radiosity system and the linearization method for applying the radiative heat flux to the thermal model. Note that the parameter for this block command will be used with the USE RADIOSITY SOLVER line command in the ENCLOSURE DEFINITION command block.

    begin Radiosity Solver Boundary condition instance name

       Convergence Tolerance {=} Tolerance

       Coupling {=} {lagged | mason | smoothed}

       Initial Guess {=} {physics | previous}

       Maximum Iterations {=} m

       Output Rule {=} {more verbose | none | summary | verbose}

       Polynomial Preconditioner Order {=} m

       Solver {=} {chaparral bicgstab | chaparral cg | chaparral gmres | coupled}

    end Radiosity Solver Boundary condition instance name

### 7.26.3.1. Line Commands

###### Convergence Tolerance

Syntax

  Convergence Tolerance {=} Tolerance

Summary

  Sets convergence tolerance.

Description

  This line command sets the convergence tolerance for the iterative solution of the radiosity system. The iterative solution will stop when the ratio of the current residual to the initial residual is less than the specified tolerance:

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Tolerance | real | 1.0e-6

###### Coupling

Syntax

  Coupling {=} {lagged | mason | smoothed}

Summary

  Specifies linearization method.

Description

  This line command specifies the linearization method used to apply the radiative heat flux to the thermal model.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
RadCouplingRule | {lagged | mason | smoothed} | MASON

###### Initial Guess

Syntax

  Initial Guess {=} {physics | previous}

Summary

  Default uses the previous solution state as an initial guess for the current solution.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
InitialGuess | {physics | previous} | PREVIOUS

###### Maximum Iterations

Syntax

  Maximum Iterations {=} m

Summary

  Sets maximum number of iterations.

Description

  This line command sets the maximum number of iterations allowed for the iterative solution of the radiosity equations. If the maximum number of iterations is exceeded, the calculation will fail and the thermal simulation will stop.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
m | integer | 300

###### Output Rule

Syntax

  Output Rule {=} {more verbose | none | summary | verbose}

Summary

  Sets the information reporting level.

Description

  This line command will set the amount of information reported to the output screen about the radiosity solution.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
OutputRule | {more verbose | none | summary | verbose} | NONE

###### Polynomial Preconditioner Order

Syntax

  Polynomial Preconditioner Order {=} m

Summary

  Sets preconditioner polynomial order.

Description

  This line command sets the polynomial preconditioner order for the iterative solution of the radiosity equations. This option only applies to the CHAPARRAL GMRES iterative solver.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
m | integer | 20

###### Solver

Syntax

  Solver {=} {chaparral bicgstab | chaparral cg | chaparral gmres | coupled}

Summary

  Chaparral solver selection for radiosity system.

Description

  This line command selects the method for solving the linear system of radiosity equations. The currently available methods are iterative linear solvers.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
RadSolveRule | {chaparral bicgstab | chaparral cg | chaparral gmres | coupled} | CHAPARRAL CG

## 7.26.4. Enclosure Definition

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  Specifies a radiation enclosure. Corresponds to an instance of radiation enclosure mechanics.

Description

  This block command is used to define an enclosure for the thermal model. There may be more than one enclosure defined for any thermal model. An enclosure definition includes the geometric aspects (list of element faces forming the surface), material properties, and setting of the algorithms for calculating the view factors between the element faces in the enclosure and the radiosity solution. The name of the enclosure is specified by the user.

  ** NOTE ** Enclosure names cannot begin with any sequence of numeric symbols (i.e.~0 - 9). This will cause a model to fail with very little in the way of error reporting.

    begin Enclosure Definition Boundary condition instance name

       Activate Mean Beam Model With Bulk Node Model

       Add Surface SurfaceList...

       Area Output VariableName

       Blocking Surfaces

       Dash Closure Metric Samples {=} NumSamp [ Tol {=} Value  ]

       Dash Solve Enclosures {=} Values...

       Dash Subfaceting Algorithm {=} {dash_dicing | symmetric_imprinting}

       Database Name {=} Filename In {ascii | binary | pnetcdf} Format

       Disable Parallel Redistribution

       Emissivity {=} Value [ On SurfaceName  ]

       Emissivity Function {=} FunctionName [ On SurfaceName  ]

       Emissivity Subroutine {=} MySub [ On SurfaceName  ]

       Emissivity Time Function {=} FunctionName [ On SurfaceName  ]

       Enable Parallel Redistribution

       Input Database Name {=} Filename

       Integrated Flux Output VariableName

       Integrated Power Output VariableName

       Matched Flux On SurfaceName {=} FluxType [ Phase {=} MaterialPhaseName  ]

       Mean Beam Length {=} l [Parameters]...

       Meshed Enclosure Is BlockList...

       Nonblocking Surfaces

       Output Database Name {=} Filename In {ascii | binary | pnetcdf} Format

       Overlapping Enclosure {=} {false | no | off | on | true | yes}

       Partial Enclosure Area {=} a

       Partial Enclosure Area Subroutine {=} FName

       Partial Enclosure Area Time Function {=} FName

       Partial Enclosure Emissivity {=} e

       Partial Enclosure Emissivity Subroutine {=} FName

       Partial Enclosure Emissivity Time Function {=} FName

       Partial Enclosure Flux Output VariableName

       Partial Enclosure Irradiance Output VariableName

       Partial Enclosure Radiosity Output VariableName

       Partial Enclosure Temperature {=} t

       Partial Enclosure Temperature Subroutine {=} FName

       Partial Enclosure Temperature Time Function {=} FName

       Preprocess Enclosures [ Options...  ]

       Radiosity Database Name {=} Filename

       Rowsum Database Name {=} Filename

       Topology Database Name {=} Filename

       Use Banded Wavelength Model ModelName

       Use Dash Enclosures [ type tol {=} Params...  ]

       Use Radiosity Solver Param0

       Use Skinned Shells On Surface SkinnedSurfaceList...

       Use Toggle Block ToggleName [ {on} ElementBlockList...  ]

       Use Viewfactor Calculation Param0

       Use Viewfactor Smoothing Param0

       Viewfactor Update {=} {affected_area | continuous | freeze | interval | only_if_geometry_changed | standard | times} [ Using Params...  ]

       Viewfactor Update Start Time Is Start_time

       begin Band BandName
       end

    end Enclosure Definition Boundary condition instance name

### 7.26.4.1. Line Commands

###### Activate Mean Beam Model With Bulk Node

Syntax

  Activate Mean Beam Model With Bulk Node Model

Summary

  Sets the bulk element representing the PMR material for the MBL (mean beam length) enclosure.

Parameter | Value | Default
--- | --- | ---
Model | string | –

###### Add Surface

Syntax

  Add Surface SurfaceList…

Summary

  Adds surfaces, by name, to a boundary condition’s extent.

Description

  This line command is used to add surfaces to the extent of a boundary condition. In Exodus II, surfaces are specified as side sets, that have a global integer identifier. For example, side set 12 would be added by this line command using the surface name surface_12. Note that in SIERRA, each element of an array of strings must be separated by whitespace.

Parameter | Value | Default
--- | --- | ---
SurfaceList | string… | –

###### Area Output

Syntax

  Area Output VariableName

Summary

  Output the area associated with this flux boundary condition.

Description

  This line triggers output of the enclosure area and volume.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –

###### Blocking Surfaces

Syntax

  Blocking Surfaces

Summary

  Specifies a blocking enclosure

Description

  This is the default behavior if neither this line command, nor the NONBLOCKING SURFACES line command are present. This line command informs Chaparral to consider blocking surfaces during the calculation of view factors. A blocking surface is defined as one or more element faces that occlude the view from any pair of element faces within the enclosure. If it is known that no blocking surfaces exist in the enclosure, the NONBLOCKING SURFACES line command can be included in the enclosure definition to reduce the compute time for view factors. Note that the BLOCKING SURFACES line command should be included if there is any doubt whether there are blocking surfaces in the enclosure.

###### Dash Closure Metric Samples

Syntax

  Dash Closure Metric Samples {=} NumSamp [ Tol {=} Value ]

Summary

  Specify number of samples for DASH closure metric and possibly an acceptable tolerance.

Description

  When using DASH enclosures one may wish to assign the number of sample points used in determining closure. Optionally, one can set the acceptable value of closure metric associated with closure.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
NumSamp | integer | –

###### Dash Solve Enclosures

Syntax

  Dash Solve Enclosures {=} Values…

Summary

  List of integer index values for Dash enclosures to perform solution. The index values must be obtained by a preprocessing step using both PREPROCESS ENCLOSURE TOPOLOGY command line at the Region level and the PREPROCESS ENCLOSURES command line in the Enclosure Definition command block.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Values | integer… | –

###### Dash Subfaceting Algorithm

Syntax

  Dash Subfaceting Algorithm {=} {dash_dicing | symmetric_imprinting}

Summary

  Specify the subfaceting algorithm type. This is a developer command.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Type | {dash_dicing | symmetric_imprinting} | –

###### Database Name

Syntax

  Database Name {=} Filename In {ascii | binary | pnetcdf} Format

Summary

  Specifies common filename to read/write viewfactors

Description

  This line command specifies the database name for both input and output of the view factors for this enclosure. The file name is provided by the user, and one of three file formats is specified.

  The ASCII format should be used only for small enclosures. This format is useful when the analyst wants to examine the values of the view factors that have been evaluated.

  The BINARY format will produce a machine-dependent file. This view-factor file can only be read on the same machine in subsequent calculations.

  Both the ASCII and BINARY file formats may only be read on the same number of processors as they were written with, and are deprecated as of Aria version 4.43.5. The replacement PNETCDF format produces a single machine-independent file that may be written or read in runs using any number of processors.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Filename | string | –
VFfileFormat | {ascii | binary | pnetcdf} | –

###### Disable Parallel Redistribution

Syntax

  Disable Parallel Redistribution

Summary

  Disable parallel redistribution of viewfactor matrix.

Description

  Ensures that the default distribution of the viewfactor matrix is distribution of rows across MPI ranks is enforced - no parallel distribution of the view factor matrix.

###### Emissivity

Syntax

  Emissivity {=} Value [ On SurfaceName ]

Summary

  Sets a constant value of emissivity for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

  Note

  If a surface is called out more than once, the emissivity definition is overwritten: last one in wins.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Value | real | –

###### Emissivity Function

Syntax

  Emissivity Function {=} FunctionName [ On SurfaceName ]

Summary

  Sets a emissivity function for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FunctionName | string | –

###### Emissivity Subroutine

Syntax

  Emissivity Subroutine {=} MySub [ On SurfaceName ]

Summary

  Sets a emissivity user subroutine for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

  Also, the software supports using locally scoped user data for most user subroutines, but I haven’t figured out a syntax for it here yet. So it is not yet supported. If you need to get data into this subroutine, use the region’s “REAL DATA” and “INTEGER DATA” line commands.

  Note

  If a surface is called out more than once, the emissivity definition is overwritten: last one in wins.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
MySub | string | –

###### Emissivity Time Function

Syntax

  Emissivity Time Function {=} FunctionName [ On SurfaceName ]

Summary

  Sets a emissivity function of time for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FunctionName | string | –

###### Enable Parallel Redistribution

Syntax

  Enable Parallel Redistribution

Summary

  Enables parallel redistribution of viewfactor matrix.

Description

  Invokes redistribution of the view factor matrix from a distribution of matrix rows across MPI ranks to a 2D distribution of row and column blocks to achieve better performance in parallel. A current limitation of this option is that the Tpetra redistribution capability will use more memory than necessary and may not be a appropriate if one is memory constrained on a platform.

###### Input Database Name

Syntax

  Input Database Name {=} Filename

Summary

  Specifies filename to read viewfactors from

Description

  This line command provides the name of the view-factor file. If this line command is present, the file containing the given view-factor matrix will be opened and read. The calculation of view factors will not take place. Note that you must also specify a value of READ for the COMPUTE RULE command in the associated VIEWFACTOR CALCULATION command block.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Filename | string | –

###### Integrated Flux Output

Syntax

  Integrated Flux Output VariableName

Summary

  Calculate the average flux associated with this flux boundary condition.

Description

  This line command specifies that, as a postprocess, the normal flux associated with this boundary condition be integrated over the surface to obtain the total power. This power is then divided by the total area of the surface to obtain the average flux on the surface, and stored in a global variable named “VariableName”. This global variable may then be output to history files, or accessed in user subroutines, etc.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –

###### Integrated Power Output

Syntax

  Integrated Power Output VariableName

Summary

  Calculate the total power associated with this flux boundary condition.

Description

  This line command specifies that, as a postprocess, the normal flux associated with this boundary condition be integrated over the surface to obtain the total power which is then stored into a global variable named “VariableName”. This global variable may then be output to history files, or accessed in user subroutines, etc.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –

###### Matched Flux On

Syntax

  Matched Flux On SurfaceName {=} FluxType [ Phase {=} MaterialPhaseName ]

Summary

  Indicates an equivalent matching flux for surfaces within the enclosure that border element blocks which do not have the ENERGY equation defined but do have an equivalent equation (such as ENTHALPY) defined. The primary use for this is in OMD simulations and should be considered at the same reliability level as OMD.

Parameter | Value | Default
--- | --- | ---
SurfaceName | string | –
{=} | {= | are | is} | –
FluxType | string | –

###### Mean Beam Length

Syntax

  Mean Beam Length {=} l [Parameters]…

Summary

  Sets the expression for the radiant decay length L for the MBL (mean beam length) enclosure.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
l | string | –
Parameters | [string]… | –

###### Meshed Enclosure

Syntax

  Meshed Enclosure Is BlockList…

Summary

  Adds blocks, by name, to the meshed enclosure extent.

Description

  In the event one wishes to solve a conduction problem within an enclosure as well as the radiation problem the interior discretization must be defined. This line command is used to add blocks to the extent of a enclosure interior. In Exodus II, surfaces are specified as side sets, that have a global integer identifier. For example, block 12 would be added by this line command using the surface name block_12. Note that in SIERRA, each element of an array of strings must be separated by whitespace.

Parameter | Value | Default
--- | --- | ---
BlockList | string… | –

###### Nonblocking Surfaces

Syntax

  Nonblocking Surfaces

Summary

  Specifies a non-blocking enclosure

Description

  See the BLOCKING SURFACES command for a complete description.

###### Output Database Name

Syntax

  Output Database Name {=} Filename In {ascii | binary | pnetcdf} Format

Summary

  Specify filename to write viewfactors to

Description

  This line command activates the output of the view factors calculated during a simulation. The file name is provided by the user, and one of three file formats is specified. See the “DATABASE NAME” line command description for more detail on the file formats.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Filename | string | –
VFfileFormat | {ascii | binary | pnetcdf} | –

###### Overlapping Enclosure

Syntax

  Overlapping Enclosure {=} {false | no | off | on | true | yes}

Summary

  Designates this enclosure as overlapping other enclosures.

Description

  On occasion one might want to define an enclosure radiation problem as a superposition of several enclosures. In this case one must designate one of the enclosures as overlapping the others in order to distinguish it from the other enclosures. This command adds a qualifier to the enclosure definition to enable making this distinction possible.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Bool | {false | no | off | on | true | yes} | –

###### Partial Enclosure Area

Syntax

  Partial Enclosure Area {=} a

Summary

  Constant value for the partial enclosure area associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
a | real | –

###### Partial Enclosure Area Subroutine

Syntax

  Partial Enclosure Area Subroutine {=} FName

Summary

  User-defined function name for the partial enclosure area associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FName | string | –

###### Partial Enclosure Area Time Function

Syntax

  Partial Enclosure Area Time Function {=} FName

Summary

  Time-dependent function name for the partial enclosure area associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FName | string | –

###### Partial Enclosure Emissivity

Syntax

  Partial Enclosure Emissivity {=} e

Summary

  Constant value for the partial enclosure emissivity associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
e | real | –

###### Partial Enclosure Emissivity Subroutine

Syntax

  Partial Enclosure Emissivity Subroutine {=} FName

Summary

  User-defined function name for the partial enclosure emissivity associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FName | string | –

###### Partial Enclosure Emissivity Time Function

Syntax

  Partial Enclosure Emissivity Time Function {=} FName

Summary

  Time-dependent function name for the partial enclosure emissivity associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FName | string | –

###### Partial Enclosure Flux Output

Syntax

  Partial Enclosure Flux Output VariableName

Summary

  Output the flux associated with the partial enclosure.

Description

  During the simulation the flux associated with the partial enclosure is output to the ExodusII file as a global variable.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –

###### Partial Enclosure Irradiance Output

Syntax

  Partial Enclosure Irradiance Output VariableName

Summary

  Output the irradiance associated with the partial enclosure.

Description

  During the simulation the irradiance associated with the partial enclosure is output to the ExodusII file as a global variable.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –

###### Partial Enclosure Radiosity Output

Syntax

  Partial Enclosure Radiosity Output VariableName

Summary

  Output the radiosity associated with the partial enclosure.

Description

  During the simulation the radiosity associated with the partial enclosure is output to the ExodusII file as a global variable.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –

###### Partial Enclosure Temperature

Syntax

  Partial Enclosure Temperature {=} t

Summary

  Constant value for the partial enclosure temperature associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
t | real | –

###### Partial Enclosure Temperature Subroutine

Syntax

  Partial Enclosure Temperature Subroutine {=} FName

Summary

  User-defined function name for the partial enclosure temperature associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FName | string | –

###### Partial Enclosure Temperature Time Function

Syntax

  Partial Enclosure Temperature Time Function {=} FName

Summary

  Time-dependent function name for the partial enclosure temperature associated with this enclosure radiation flux boundary condition.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FName | string | –

###### Preprocess Enclosures

Syntax

  Preprocess Enclosures [ Options… ]

Summary

  Preprocess enclosures subject to options: ORIGINAL_FACES, ENCLOSURE_FACETS, ENCLOSURE_FACET_EDGES, CONTACT_FACETS, CONTACT_FACET_EDGES and COARSE_MESH. When invoked at Region preprocessing is performed and the simulation will terminate.

Description

  For debug and inspection purposes the surfaces defined in the enclosure definitions will be processed, then output to the exodus database before terminating the simulation. If no options are chosen the default is to select all the available information. Options are: ORIGINAL_FACES, ENCLOSURE_FACETS, ENCLOSURE_FACET_EDGES, CONTACT_FACETS, CONTACT_FACET_EDGES and COARSE_MESH. Facets are output as triangle elements, edges as bars and faces as shell elements.

###### Radiosity Database Name

Syntax

  Radiosity Database Name {=} Filename

Summary

  Specify filename to write enclosure rowsum error and radiosity results to

Description

  This line command activates the output of the view factor rowsum error calculated during a simulation. Additionally, this file will be used to also output the radiosity and flux values during subsequent calls to the radiosity solver. The file name is provided by the user and the output format is ExodusII. This file is useful when the analyst wants to where in the enclosure the maximum errors are occurring. The rowsum error is given by [ 1-sum_{j = 1}^{N_{facets}} F_{ij} ] for each row i in the view-factor matrix (which corresponds to a face in the enclosure). Use of this option will negatively affect performance and is intended for use by developers.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Filename | string | –

###### Rowsum Database Name

Syntax

  Rowsum Database Name {=} Filename

Summary

  Specify filename to write enclosure rowsum error results to

Description

  This line command activates the output of the view factor rowsum error calculated during a simulation. The file name is provided by the user and the output format is ExodusII. This file is useful when the analyst wants to where in the enclosure the maximum errors are occurring. The rowsum error is given by [ 1-sum_{j = 1}^{N_{facets}} F_{ij} ] for each row i in the view-factor matrix (which corresponds to a face in the enclosure).

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Filename | string | –

###### Topology Database Name

Syntax

  Topology Database Name {=} Filename

Summary

  Specify filename to write enclosure topology to

Description

  This line command activates the output of the enclosure topology, taking into account all specified symmetry. The file name is provided by the user and the output format is ExodusII.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Filename | string | –

###### Use Banded Wavelength Model

Syntax

  Use Banded Wavelength Model ModelName

Summary

  Use a specified banded wavelength model for use in enclosure radiation.

Description

  Requests that a specific banded wavelength model named ModelName, be associated with an enclosure, where the ModelName is defined outside of the enclosure definition block. Only one BANDED WAVELENGTH MODEL can be used for an enclosure.

Parameter | Value | Default
--- | --- | ---
ModelName | string | –

###### Use Dash Enclosures

Syntax

  Use Dash Enclosures [ type tol {=} Params… ]

Summary

  Perform DASH contact search on the enclosure surfaces.

Description

  Performing a DASH contact search on the enclosure surfaces will prevent any faces in contact from being processed as part of an enclosure. Optionally one may define a relative tolerance based upon the characteristic element length, or absolute tolerances in positive and negative directions from the enclosure surface.

###### Use Radiosity Solver

Syntax

  Use Radiosity Solver Param0

Summary

  Specifies which radiosity solver to use.

Description

  This line command is used to identify the radiosity solver for use with this enclosure radiation problem. The details of the radiosity solver are defined using the RADIOSITY SOLVER command block. The parameter for this line command is the parameter used with the RADIOSITY SOLVER block command.

Parameter | Value | Default
--- | --- | ---
Param0 | string | –

###### Use Skinned Shells On Surface

Syntax

  Use Skinned Shells On Surface SkinnedSurfaceList…

Summary

  Automatically created skinned shells for the specified surfaces and use them instead of the surface for enclosure radiation calculations

Description

  Automatically created skinned shells for the specified surfaces and use them instead of the surface for enclosure radiation calculations. This may be required, for example, if the block attached to the enclosure surface is undergoing mesh refinement and you do not want to re-do the view factor calculation every time the surface mesh is modified. This option will create a shell block that’s a copy of the specified surface but does not participate in mesh refinement. Temperatures are transferred to the shell and fluxes returned to the source surface using a contact algorithm. For purposes of error estimation, be aware that using this capability means that the view factor calculation on this surface will always be at the resolution of the mesh on the source surface in the input mesh file.

Parameter | Value | Default
--- | --- | ---
SkinnedSurfaceList | string… | –

###### Use Toggle Block

Syntax

  Use Toggle Block ToggleName [ {on} ElementBlockList… ]

Summary

  Specification for toggling entities in the computational model based on Toggle Block parameters. When used at the region level, the list of element blocks to be toggled must be provided. Otherwise a listing of entities is not needed as the Toggle Block will be associated with the command line or the enclosing command block.

Parameter | Value | Default
--- | --- | ---
ToggleName | string | –

###### Use Viewfactor Calculation

Syntax

  Use Viewfactor Calculation Param0

Summary

  Specifies which view factor calculation to use.

Description

  This line command is used to specify the name of a method for calculating view factors defined using the VIEWFACTOR CALCULATION command block. The parameter for this line command is the parameter used to name the VIEWFACTOR CALCULATION block command.

Parameter | Value | Default
--- | --- | ---
Param0 | string | –

###### Use Viewfactor Smoothing

Syntax

  Use Viewfactor Smoothing Param0

Summary

  Specifies which view factor smoother to use.

Description

  This line command is used to specify the name of a method for smoothing view factors defined using the VIEWFACTOR SMOOTHING command block. The parameter for this line command is the parameter used with the VIEWFACTOR SMOOTHING block command.

Parameter | Value | Default
--- | --- | ---
Param0 | string | –

###### Viewfactor Update

Syntax

  Viewfactor Update {=} {affected_area | continuous | freeze | interval | only_if_geometry_changed | standard | times} [ Using Params… ]

Summary

  Specify the viewfactor re-compute strategy.

Description

  The view factor calculation oftentimes dominates the computational cost of a thermal analysis. Thus for cases in which only the geometry changes due to surface deformation and the analyst views the change to be small enough so as to not affect the view factors greatly, one can select one of the strategies below for update of the view factors.

  Warning

  This command has only been enabled to work with models with mesh motion and will not work with standard element death.

  standard is the default re-compute strategy, update on mesh change.

  freeze means the view factor update is deactivated for subsequent updates. Thus the first view factor calculation determines the view factors used throughout the simulation.

  continuous means the view factors will be computed every time step of a transient simulation.

  affected_area is relevant only when used with Element Death. For every view factor calculation the enclosure surface area is computed and stored as a reference area. At subsequent solution steps the area corresponding to elements which are candidates for Element Death is accumulated. The radio of candidate death element area to the original area is used as the criteria of whether Element Death and a new view factor update will occur. If affected_area is chosen and Element Death is not present the re-compute strategy will revert to standard. Here the Params value is the ratio of affected area to total area for which element death can occur.

  Warning

  The affected_area option has not yet been enabled for use and will not control the viewfactor update frequency.

  interval specifies the time interval between view factor updates. Here Params is a single value time increment.

  times selects specific times at which the view factors are recalculated. Here Params can be several discrete time values.

  For interval and times, one can also select a time at which view factor updates are considered using the view factor update start time command line.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
UpdateMethod | {affected_area | continuous | freeze | interval | only_if_geometry_changed | standard | times} | STANDARD

###### Viewfactor Update Start Time

Syntax

  Viewfactor Update Start Time Is Start_time

Summary

  Specify start time for possible re-compute of viewfactors.

Description

  Specify the time after which viewfactor re-compute can occur. Command is active only for UPDATE FACTOR method = TIMES or INTERVAL.

Parameter | Value | Default
--- | --- | ---
Start_time | real | 0.0

## 7.26.5. Banded Wavelength Model

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  This command block specifies the wavelength distribution for a banded wavelength model.

Description

  Defines a piecewise constant banded wavelength discretization model of the thermal wavelength spectrum and associate it with name ModelName. The same ModelName can be used for different boundary conditions.

    begin Banded Wavelength Model ModelName

       Band BandName {=} LowValue HighValue

    end Banded Wavelength Model ModelName

### 7.26.5.1. Line Commands

###### Band

Syntax

  Band BandName {=} LowValue HighValue

Summary

  Specify the range of a wavelength band in microns for a surface or collection of surfaces undergoing radiative heat transfer.

Description

  Defines the upper and lower limits of a wavelength band in microns . Upper and lower limit values can intersect those of adjacent bands but cannot overlap into previously a defined BAND.

Parameter | Value | Default
--- | --- | ---
BandName | string | –
{=} | {= | are | is} | –
LowValue | real | 0.0
HighValue | real | REAL_MAX

## 7.26.6. Band

Scope

  Enclosure Definition

Summary

  This nested command block specifies the emissivity distribution for the surfaces in the enclosure for the given band.

Description

  Defines the emissivity distribution for the surfaces and/or default values for the band with name bandName.

    begin Band BandName

       Emissivity {=} Value [ On SurfaceName  ]

       Emissivity Function {=} FunctionName [ On SurfaceName  ]

       Emissivity Subroutine {=} MySub [ On SurfaceName  ]

       Emissivity Time Function {=} FunctionName [ On SurfaceName  ]

    end Band BandName

### 7.26.6.1. Line Commands

###### Emissivity

Syntax

  Emissivity {=} Value [ On SurfaceName ]

Summary

  Sets a constant value of emissivity for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

  Note

  If a surface is called out more than once, the emissivity definition is overwritten: last one in wins.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Value | real | –

###### Emissivity Function

Syntax

  Emissivity Function {=} FunctionName [ On SurfaceName ]

Summary

  Sets a emissivity function for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FunctionName | string | –

###### Emissivity Subroutine

Syntax

  Emissivity Subroutine {=} MySub [ On SurfaceName ]

Summary

  Sets a emissivity user subroutine for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

  Also, the software supports using locally scoped user data for most user subroutines, but I haven’t figured out a syntax for it here yet. So it is not yet supported. If you need to get data into this subroutine, use the region’s “REAL DATA” and “INTEGER DATA” line commands.

  Note

  If a surface is called out more than once, the emissivity definition is overwritten: last one in wins.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
MySub | string | –

###### Emissivity Time Function

Syntax

  Emissivity Time Function {=} FunctionName [ On SurfaceName ]

Summary

  Sets a emissivity function of time for a defined surface. If the optional parameters are not included, then this is the default emissivity for the enclosure. Otherwise it is only applied to the indicated surface.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
FunctionName | string | –