7.26. Enclosure Radiation

This section is referenced in the following other sections

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

$\frac{\mbox{Std. Dev. of} F_{ij}}{F_{ij}} \lessthan tol_{1}$

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

$\mbox{Std. Dev. of} F_{ij} \lessthan tol_{2}$

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

Reciprocity enforcement using the specified RECIPROCITY RULE
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: $\left| 1 - \sum F_{ij} \right| \lessthan tol$ 2) LEAST-SQUARES: $\| r \| \lessthan tol$

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

$\sum F_{ij} = 1.0$

and the reciprocity property of view factors given by

$A_i F_{ij} = A_j F_{ji} .$

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,

$A_i F_{ij} = A_j F_{ji}$

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, $F_{ij}$ and $F{ji}$ , are nonzero, these factors are adjusted by averaging $A_i F_{ij}$ and $A_j F_{ji}$ .

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, $p$ , used for the weights in the LEAST-SQUARES smoothing algorithm

$w_{ij} = {F^p}_{ij} .$

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:

$\frac{\left\| r \right\|}{\left\| r_0 \right\|} < tol$

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 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 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 $\mu m$ for a surface or collection of surfaces undergoing radiative heat transfer.
Description: Defines the upper and lower limits of a wavelength band in microns $\mu m$ . 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	–