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Chapter 68: Collection and Primitives Radiation

68 Collection and Primitives

Radiation

Summary 1242

Introduction 1243

Modeling Details 1243

Solution Highlights 1243

Results 1250

Modeling Tips 1251

Input File(s) 1252

Video 1252

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Summary

Title Chapter 68: Collection and Primitives Radiation

Features: Enclosure Radiation

Primitive modeling

Small facet, Collection (Super Element), and Primitive radiation

Geometry & Boundary

Conditions

Material properties K = 0.001 W/m/oC, Emissivity, = 1.0, Absorptivity, = 1.0

Analysis characteristics Solution 400 / RC Network solver. Steady and transient thermal analysis.

Element type 4-node shell element CQUAD4

FE results

Space T = -273.15 oCRadiation insulated

upper side

Radiation insulated

Inner side

Normal Flux

1000 W/m2

Inner Side

Plate: 1.5 m x 1.5 m x 1 mm

Sphere: 1 m dia, t = 1 mm

Distance from Sphere center

to plate = 1 m

Small Facets

(1113 sec)

Collection (Super Element)

(6 sec)

Primitives

(3 sec)

104.8

Temperatures

104.6 104.3

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Introduction

This problem demonstrates three enclosure radiation loads of SOL 400 RC Network Solver: Small Facets, Collection(Super Element), and Primitives. Three methods will be used to solve the same model - small facet method, super

element method and primitive method. You can compare the speed and accuracy among the three methods.

Modeling DetailsThis model consists of a hemi-sphere and a plate. They are all primitive surfaces. The hemi-sphere and plate radiate

to each other, the other sides are radiation insulated. A heat flux 1000 W/ m is applied to the inner side of the hemi-sphere. A black coating is applied on the surface of both hemi-sphere and plate. An extremely low conductivity

material and extremely thin 2-D shell property are used to show the pour radiation effect.

Figure 68-1 Model Geometry and Materials

Solution HighlightsEnclosure Radiation has three options: Small Facets, Collection (Super Element), and Primitives. The small facets

method is the traditional way of FEM modelers to calculate radiation view factors. The collection and primitives are

the unique methods for speeding up radiation calculation in RC Network Solver. All the facets in the application region

will be treated as one radiation node. This makes the radiation analysis much faster and more efficient. The primitive

method also utilizes true geometric shapes for radiation analysis. A special algorithm is developed to match the

radiation results back to the finer conduction mesh. More details on collection and primitives can be referenced in

MSC Sinda for Patran user's guide.

RC Network Solver uses VIEWEX entry to simulate the enclosure radiation loads. RADC entry is used to represent the

MLI or Coating materials. These two entries are introduced in Chapter 66: Satellite in Orbit. The SET3 and RADCOL

cards are used to represent the collection (Super Element). The SET3 and PRIMx cards are used to represent the

primitives.

CHBDYE 9346 8735 1 2 2

CHBDYE 9347 8736 1 2 2

Space T = -273.15 oCRadiation insulated

upper side

12x12 mesh

Radiation insulated

Inner side

Normal Flux

1000 W/m2

Inner Side

Plate: 1.5 m x 1.5 m x 1 mm

Sphere: 1 m dia, t = 1 mm

Distance from Sphere center

to plate = 1 m

AxB mesh = 1x1

K= 0.001 W/m/oCCp = 1 J/Kg/oC

= 1 Kg/m3

Emissivity = 1

Absorptivity = 1

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$!

SET3 2 ELEM 9043 9044 9045 9046 9047 9048+

+ 9049 9050 9051 9052 9053 9054 9055 9056+...

$! Radiation Collection

RADCOL 3 2 2 2

...

CHBDYE 9746 930 1 3 2

CHBDYE 9747 931 1 3 2

$!

SET3 4 ELEM 9348 9349 9350 9351 9352 9353+

+ 9354 9355 9356 9357 9358 9359 9360 9361+...

$! Primitive Shape

$!----------------------------------------------------------------------------!$

PRIM1 2 3 2 3

-0.75 -0.75 1. 0.75 -0.75 1.

-0.75 0.75 1. 1 1

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1245CHAPTER 68

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Specifies a collection of boundary elements to be used as a single face in the radiation calculation. This will decrease

computation time at the small cost of accuracy. Computational savings and accuracy are dependent on the coarseness

of the collection versus the constituents. View factors of the collection are redistributed across the elements for

calculation of the radiative energy transfer.

Format

Example

Remarks

1. This entry is for RC Network solver only.

2. IVIEWF/IVIEWB will default to 0 if left blank. This would indicate that the corresponding front and/or back do

participate in the radiation.

3. IF an IVIEWF is specified, there must also be a RADMIDF for surface material properties. If an IVIEWB is

specified there must also be a RADMIDB for surface material properties.

RADCOL Radiation Collective Entity

1 2 3 4 5 6 7 8 9 10

RADCOL RADCOLID 701 2 1.0

1 2 3 4 5 6 7 8 9 10

RADCOL 101 5 6 2 3 7

Field Contents Type Default

RADCOLID Radiation Collection identification number. I 0 Required

IVIEWF A VIEW entry identification number for the front face. I 0 0

IVIEWB A VIEW entry identification number for the back face. I 0 0

RADMIDF RADM identification number for the front face I 0 0

RADMIDB RADM identification number for the back face. I 0 0

SET3 idn ID of the element collection to be considered a super

element.

I 0

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Specifies the properties of geometric primitives to be used in radiation calculations in place of elements.

Format

PRIMx Thermal Geometric Primitives for RC Radiation

1 2 3 4 5 6 7 8 9 10

PRIM1 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) A_mesh B_mesh

1 2 3 4 5 6 7 8 9 10

PRIM2 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) P4(1) P4(2) P4(3) A_mesh B_mesh

1 2 3 4 5 6 7 8 9 10

PRIM3 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) A_mesh B_mesh

1 2 3 4 5 6 7 8 9 10

PRIM4 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) Diam1 Diam2 Angle1 Angle2

A_mesh B_mesh

1 2 3 4 5 6 7 8 9 10

PRIM5 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) Diam1 Angle1 Angle2 A_mesh B_mesh

1 2 3 4 5 6 7 8 9 10

PRIM6 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) Diam1 Diam2 Angle1 Angle2

A_mesh B_mesh

1 2 3 4 5 6 7 8 9 10

PRIM7 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) Diam1 Angle1 Angle2 Trunc1 Trunc2

A_mesh B_mesh

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1 2 3 4 5 6 7 8 9 10

PRIM8 PRIMID IVIEWF IVIEWB RADMIDF RADMIDB SET3ID +

+ P1(1) P1(2) P1(3) P2(1) P@(2) P2(3) +

+ P3(1) P3(2) P3(3) Diam1 Angle1 Angle2 Trunc1 Trunc2

A_mesh B_mesh

Field Contents Type Default

PRIMID Primitive identification number; unique to all

other PRIMx

I 0 Required

SET3 ID ID of the element collection to which thisprimitive describes. This collection acts as the

elements that will exist in the thermal model,

but the collection will be absent from the

radiation model. Instead, the primitive will be

used to calculate radiation and be

redistributed back onto the elements. All

radiation properties for the primitive will be

applied to the element collection and must beconsistent across.

I > 0 Required

RADMID ID of the radiation material properties used to

describe this primitive for analysis.

Pi(a) The position of point i in the a axis as

described in the correlating picture. For

example, P2(2) denotes the y coordinate of

the second point. Position is always describedin global coordinates.

R Required

Diamx Diameter x of the primitive if applicable and

as described in the correlating picture.

R 0.0 Required

Anglex Angle x of the primitive if applicable and as

described in the correlating picture.

0 R 360.0 Required

Truncx Truncation x of the primitive if all are

pickable and as described in the correlatingpicture.

R 0 for PRIM8 Required

-0.5*Diam1 R 0.5*Diam1 for PRIM7

A-mesh Number of mesh spaces in parametric

direction-1 as described in the correlating

picture.

I 0 Required

B_mesh Number of mesh spaces in parametric

direction-2 as described in the correlatingpicture.

I 0 Required

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Remarks

1. This entry is for RC Network solver only.

2. SET3 should include all the elements which belong to this primitive. It will cause wrong results if only a partial

of the elements are included.

3. PRIMID should be unique across all primitives (PRIMx) in the model.

4. About the primitives:

PRIM1: Rectangle

PRIM2: Quad

PRIM3: Triangle

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PRIM7: Sphere

PRIM8: Parabolic

Results

Figure 68-2 Temperature contour of Model for Case 1 (Steady State)

Small Facets

(1113 sec)

Collection (Super Element)

(6 sec)

Primitives

(3 sec)

104.8

Temperatures

104.6 104.3

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The following form illustrates the Thermica execute times and temperature results. (Windows XP v2002 SP3, Dell

Precision | M65 laptop, Intel Core(TM) 2 CPU, T7200@2.00GHz, 997MHz, 3.25GB of RAM).

Modeling TipsAs you can see, the temperature results are about the same, but the collection and primitives methods are much faster

then the traditional small facets method. Because of the feature of the re-match algorithm, no obstructions between the

two collections or primitives are allowed; otherwise we may lose some accuracy.

The parabolic primitive has not been supported yet in SimXpert, but MD Nastran/RC Network Solver supports that.

In MSC Sinda for Patran, you can put multiple primitives inside one application region, the translator will

automatically separate them to be multiple single- primitive loads, but SimXpert does not support this feature, one

single primitive is required for one primitive load.

You can preview the AB mesh of the primitive (Figure 68-3). These AB mesh is used to form the radiation model in

Thermica or other external radiation codes. The AB mesh does not have to be congruent with the conduction mesh.

Figure 68-3 AB mesh preview in SimXpert

Table 1-1 Speed and Result Comparison among the Three Methods (Ray count: 500,000)

Radiation Executing Time (s) Temperature Result (C)

Small facets method 1113 -79.74 to 104.8

Collection method 6 -79.67 to 104.6

Primitives method 3 -79.53 to 104.3

MD D t ti P bl1252

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Input File(s)

VideoClick on the image or caption below to view a streaming video of this problem; it lasts approximately 30 minutes and

explains how the steps are performed.

Figure 68-4 Video of the Above Steps

Files DescriptionQT16_hemi_sph_sf.dat MD Nastran SOL400/RC Network Solver thermal input file

QT33_hemi_sph_se.dat MD Nastran SOL400/RC Network Solver thermal input file

QT32_hemi_sph_pr.dat MD Nastran SOL400/RC Network Solver thermal input file

Space T = -273.15 oCRadiation insulated

upper side

Radiation insulated

Inner side

Normal Flux

1000 W/m2

Inner Side

Plate: 1.5 m x 1.5 m x 1 mm

Sphere: 1 m dia, t = 1 mm

Distance from Sphere center

to plate = 1 m

http://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch068/QT16_hemi_sph_sf.dathttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch068/QT33_hemi_sph_se.dathttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch068/QT32_hemi_sph_pr.dathttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/training_videos/mdug/ch068/2010/ch068.swfhttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch068/QT32_hemi_sph_pr.dathttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch068/QT33_hemi_sph_se.dathttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch068/QT16_hemi_sph_sf.dat