Card 2a - Program Control

M

M defines which modules are to be executed in the thermal solver. Different values of M can be combined to run multiple modules simultaneously. For example, if M = 3, this means M = 1 + 2, and both the COND and VUFAC modules will be executed.

M = 0 executes modules MAIN, DATACH, ECHOS. This option is always triggered and performs data checking.
M = 1 executes module COND. It computes capacitances, conductive conductances, and hydraulic resistances from geometry. Two methods for calculating conductances are available: the element center method and the element CG method. The CG method, which is recommended, can be specified with a Card 9 PARAM COND NEW option.
M = 2 executes module VUFAC. It computes view factors, solar view factors, Earth view factors, albedo factors, and thermal couplings. For this option, you also need to specify Card 6 Request.
M = 4 executes module GRAYB. It computes radiative conductances from view factors. If there are no Card 6 view factor requests, and no restart run (no MODLF or VUFF files present), then the GRAYB module is not executed.
M = 8 (Obsolete) executes module GRAYB. It computes the solar spectrum gray body view factor matrix from view factors, which can be used to calculate solar spectrum heat loads in the POWER module. Any existing solar spectrum gray body view factor matrix on file VUFF will be overwritten. This is an obsolete option, which is not recommended.
M = 16 (Obsolete) executes module GRAYB. It computes the IR spectrum gray body view factor matrix from view factors, which can be used to calculate IR spectrum heat loads in the POWER module. Any existing IR spectrum gray body view factor matrix on file VUFF will be overwritten. This is an obsolete option, which is not recommended.
M = 32 executes module POWER. It computes collimated (sun) solar spectrum heat loads. Solar view factors, view factors, and the PSUN parameter are necessary for this calculation. If there are no Card 6 solar spectrum view factor (solar view factor, orbital view factor, heat flux view factor) requests, and it is not a restart run (i.e., there are no files MODLF or VUFF present), then the POWER module is only entered but not executed.
M = 64 executes module POWER. It computes IR spectrum heat loads. Earth view factors, view factors, and the PIR parameter are necessary for this calculation. If there are no Card 6 solar spectrum view factor (solar view factor, orbital view factor, heat flux view factor) requests, and it is not a restart run (i.e., there are no files MODLF or VUFF present), then the POWER module is only entered but not executed.
M = 128 executes module POWER. It computes diffuse solar spectrum (e.g., albedo) heat loads. Albedo factors or heat flux view factors, view factors, and the PSUN parameter are necessary for this calculation. If there are no Card 6 solar spectrum view factor (solar view factor, orbital view factor, heat flux view factor) requests, and it is not a restart run (i.e., there are no files MODLF or VUFF present), then the GRAYB module is only entered but not executed.

N

N controls the input/output format. You can specify different options by setting the value of N. Multiple options can be combined by summing their corresponding codes.

N = 0 specifies that no options are selected.
N = 8 specifies NASTRAN format input, where all of Card 4 is a NASTRAN bulk data deck.
N = 16 specifies NASTRAN format output. If the Analyzer is run, NASTRAN element temperatures are written on FMODLF file.
N = 512 specifies that the VUFAC module does not write the details of the view factor calculations to [Simulation name]_report.log in order to reduce its size.
N = 1024 specifies that Card 4 and 5 data is read from the VUFF file.

MESH

MESH defines the element subdivision for view factor shadowing, ray tracing, and Card 6e thermal coupling calculations performed by the VUFAC module.

Unshadowed view factors and solar view factors are calculated exactly, and are not affected by the MESH value.

MESH = 0 specifies that no subdivision is performed.
MESH = 1,2,3,4,5 specifies each beam is subdivided into MESH line segments, and each planar element is subdivided into NV × MESH² triangular sub-elements, where NV is the number of nodes in the element.

The Card 6f MESH Redefinition overrides the MESH parameter value.


Beam MESH = 0	Triangle MESH = 0	Quadrilateral MESH = 0
Beam MESH = 1	Triangle MESH = 1	Quadrilateral MESH = 1
Beam MESH = 2	Triangle MESH = 2	Quadrilateral MESH = 2

RK

RK is used by the GRAYB module with Gebhardt's method, but not with Oppenheim's method, to either eliminate insignificant radiative conductances, or to connect them to element's parameter KSP. A radiative conductance is considered insignificant if its gray body view factors between two elements are less than the absolute value of RK multiplied by the largest gray body view factor of either element to a non-space element. The value of RK must be between –1 and 1.

RK > 0 eliminates the radiative conductance, unless it is connected to a space element defined on a Card 5 SPACE.
RK < 0 connects the conductance to the KSP element, unless KSP is a space element.
RK = 0 defaults to RK = 1E-4.
RK = 0.05 reduces the number of radiative conductances without significantly impacting accuracy.

KSP

KSP is used by the GRAYB module to create residual view factors, computed as 1-VFSUM for Gebhardt's method when the view factors do not sum to unity. Generally view factors do not sum to unity due to approximations made during the shadowing calculation process.

KSP = 0 creates self-view factors, calculated as 1−VFSUM, meaning that the elements are made to "see" themselves. This option is particularly useful when there are many low-emissivity elements present.
KSP = 1000000 adjusts the gray body view factors to compensate for residual view factors. However, this method is obsolete and does not work with Oppenheim's Method.
KSP = NSP creates view factors equal to 1−VFSUM to the element NSP. NSP must correspond to the space element number defined in Card 5d. If multiple enclosures exist, each enclosure is flagged to indicate whether it can "see" space. An enclosure is characterized as being able to "see" space if at least one element of that enclosure "sees" a space element. If an enclosure cannot "see" space, the KSP = 0 option is applied for that enclosure. This prevents improper space couplings between enclosures that do not see space, allowing inside and outside enclosures to be safely mixed.
KSP = 2000000 is similar to KSP = NSP, but the space element number is obtained from the Card 5d Space Element.
KSP = 3000000 attempts to iteratively adjust the shadowed view factors proportionally in order to reduce residual view factors. This is the recommended option for most cases.

SIGMA

SIGMA is the Stefan-Boltzmann constant, expressed in approximate units e.g., 0.1714×10^-8 Btu/hr·ft²·R⁴ , or 5.6696×10^-8 W/m²·K⁴, or 3.6577×10^-11W/in²·K⁴.

PSUN

PSUN is the collimated solar spectrum radiative source's (sun's) power output per unit area arriving at the element. PSUN is used by the POWER module in solar spectrum heat load calculations (M = 32 or M = 128). Typical values are 429±7 Btu/hr·ft²or 1353± 21 W/m².

IA

IA is used if a sinda85 output is requested with Card 9 PARAM SINDA85.

IA = 0 creates a transient format output on file sinda85.dat.
IA = -99990 creates a steady-state format output on file sinda85.dat.

TLIN

TLIN is used by the MEREL module to linearize radiative conductances during substructuring and Card 9 PARAM THIN model thinning operations, as( T₁+T₂)(T₁² +T₂²), where:

T₁ represents the typical estimated absolute temperature of the elements to be eliminated.
T₂ is the typical absolute temperature of their surrounding environment.

Only those conductances that are connected to both radiative and conductive elements are linearized.

PIR

PIR is the heat load per unit area leaving the surface of the Earth. PIR is used by the POWER module (M = 64) to calculate Earth heat loads. A typical value for PIR for Earth heat load calculations is 75 BTU/hr/ft² or 236 W/m².

Code example


7 0 1 0 0 84 1.713E–9 440 0 26463592 80 $ CARD 2A
$ The VUFAC, GRAYB and COND modules will be executed.