*PERIODIC
16.5 *PERIODIC: Define periodic symmetry for a cavity radiation heat transferanalysis.
This option is used to define cavitysym metry by periodic repetitionin a given direction. Itcan be used only
following the *RADIATION SYMMETRYoption.
Product: ABAQUS/Standard
Type: History data
Level: Step
References:
•“Cavity radiation,” Section 32.1.1of the ABAQUS Analysis User ’sManual
•*RADIATIONSYMMETRY
Required parameter:
TYPE
Set TYPE=2D to create a cavity composed of the cavity surface definedin the model and a series
of similar images generated by its repetition according to a two-dimensionaldistance vector. The
repeated images are bounded by lines parallel to line (see Figure 16.5–1). The distance vector
must be defined so that it points away from line and into the domain of the model. This option
can be used only for two-dimensional cases.
Set TYPE=3D to create a cavity composed of the cavity surface defined in the model and a
seriesof sim ilarim ages generatedby its repetition according to a three-dimensional distance vector.
The repeated images are bounded by planes parallel to plane (see Figure 16.5–2). Thedistance
vector must be defined so that it pointsaway fromplane and into the domain of the model. This
option can be used only for three-dimensional cases.
Set TYPE=ZDIR to create a cavity composed of the cavity surface definedin the model and
a series of similar images generated by its repetition in the z-direction. The repeated images are
bounded by lines of constant z-coordinate (see Figure 16.5–3). The z-distance vector must be
defined so that it points away from the z-constant periodic symmetry reference line and into the
domain of the model. This option c an be used only for axisymmetric cases.
Optional parameter:
NR
Set this parameter equal to the number of repetitionsused in the numerical calculation of the cavity
viewfactorsresulting from the periodic symmetry. The result of this symmetry is a cavity composed
ofthe cavity surface defined in the model plus twice NR similar images, since the periodic symmetry
16.5–1
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