Card 9 - LAYER Layer Property Definition

This optional card defines the layer properties of non-homogeneous multilayer Card 5 shell elements.

Parameters: KODE, N1, T1, T2, T3, T4, T5, T6, T7, T8

KODE

KODE is the code LAYER (or 67)

N1

N1 is the LAYER Card ID. Must be the same as the associated PROP Card ID of the top element in the layer.

T1

T1 is the layer number. T1 must be > 1, since it references the layer below the top layer.

T2

T2 is the MAT Card ID of the layer, in the form Mn, where n is the ID number.

T3

T3 is the PROP Card ID of the layer in the form Pn, where n is the ID.

T4

T4 is the OPTICAL Card ID of the front side of the layer, in the form On, where n is the ID. Must be zero if not used.

T5

T5 is the OPTICAL Card ID of the reverse side of the layer, in the form On, where n is the ID. Must be zero if not used.

T6

T6 is the principal material angle in degrees for orthotropic materials, measured relative to the principal material axis of the top layer, as defined on its MATVEC Card. This requires that if a layer is orthotropic, the top layer should also be specified as an orthotropic element. Must be zero if not used.

T7

T7 is the heat transfer coefficient that determines the magnitude of the transverse conductive coupling between the layers.

If T7 is not zero, a conductive coupling of magnitude G is created between the element and the element of the layer above it.

If T7 is zero, but the thermal conductivity of the element and the element above it are not, the transverse conductance is calculated from the layer thicknesses and thermal conductivities:

If T7 is zero or blank, and either the thermal conductivity of the layer, or that of the layer above, is table-dependent, then, instead of creating a single conductance between the two layers, an additional calculation point is inserted between the layers, and a transverse conductance is created between this calculation point and the layer, and between this point and the layer above.

If T7 has the value 1.E-20 or less, then no thermal coupling is created between the layers.

T8

T8 defines the magnitude of the radiative conductance between the layer and the layer above.

If T8 is neither zero nor blank, then a radiative conductance of magnitude Grad is created between the layers:

If T8 is zero or blank, and emissivities are defined for both the top surface of the layer and the reverse side of the layer above, view factors will be automatically requested between the layers. View factors from inner layers are calculated only to adjacent layers, and are set to unity.

If T8 has the value 1.E-20 or less, then no radiative thermal coupling is created between the layers.

Code example


PROP 2 SHELL .6          $ PROP Card of top layer
LAYER 2 2 M4 P6 O5 O6 0  $ Second layer of elements referencing PROP Card 2
LAYER 2 3 M4 P6 O5 O6 0  $ Third layer
MAT 4 KTHERM .67         $ MAT Card of the layers
OPTICAL 5 E .5           $ Front optical property
OPTICAL 6 E .6           $ Rear optical property
PROP 6 SHELL 3.7         $ PROP Card of the layers

Notes

Non-homogeneous multilayer elements are shell elements with different layers. Each layer may have different optical, physical, and material properties. Radiation, in-plane conduction, and conduction to an adjacent layer are supported by each layer.

By contrast, all layers of homogeneous multilayer elements (defined with non-zero field T3 on a PROP Card for shell elements) have the same material and physical properties, the layers cannot radiate to each other, and in-plane conduction is supported only on the central layer.

The following are the highlights of the way non-homogeneous multilayer elements are handled in TMG:

  • An element is defined to be a non-homogeneous multilayer element if it has LAYER Cards defined. The LAYER Card ID (field N1) must be the same as the PROP Card ID of the top layer.
  • Each LAYER Card generates a shell element behind the top layer, with MAT, OPTICAL, and PROP Card properties defined on the LAYER Card. The properties of the top layer are obtained from its own MAT, OPTICAL, and PROP Cards. The top layer does not have a LAYER Card.
  • Each internal layer’s element is generated at the center of the layer, while each external (top and bottom) layer’s element is generated on its outer surface. Example: for a 4-layer element, with thicknesses t1, t2, t3, and t4, the distances from top to bottom between the elements will be (t1+t2/2), (t2/2+t3/2), (t3/2+t4). Note that the total thickness adds up to t1+t2+t3+t4.
  • If a reverse side is specified on a Card 6 radiation request, e.g. on a Card 6r - View Factor Request in an Enclosure. It will be interpreted to be the reverse side of the bottom layer.
  • Reverse side elements for a layer are generated if its reverse side optical properties are defined on its OPTICAL or MAT Cards. For the top layer a reverse side may also be defined by a REVNODE Card.
  • If a layer can conduct laterally, it will conduct to the corresponding layer of an adjacent multilayer element. For example, the third layer of a multilayer element conducts to an adjacent multilayer element’s third layer.
  • “Hanging” layers do not conduct laterally – e.g. if a multilayer element has 4 layers and the adjacent element has only 3 layers, the 4th layer will not conduct the adjacent element.
  • A layer’s thermal conductivities may be specified to be constant or table-dependent, isotropic or orthotropic.
  • A beam element is connected to a multilayer element is considered to be connected to all its layers, i.e. a “short” is formed connecting the layers.
  • A layer of a non-homogeneous multilayer element may not be specified to be a multilayer element.
  • Temperature and heat load boundary conditions may be applied to specific layers. For more information, see Card 9 - SINK Elements and Card 9 - QNODE Heat Loads.
  • The surface normals of adjacent non-homogeneous multilayer elements sharing common nodes should be oriented in a consistent direction, for example they should not point in opposite directions.

The following is an example of a 3-layer non-homogeneous multilayer element, with the referenced MAT, PROP, and OPTICAL Cards.