Initial Values (Thin Layer, Thin Film, Fracture, and Heat Transfer in Shells Interface)
This node adds an initial value for the temperature that can serve as an initial condition for a transient simulation or as an initial guess for a nonlinear solver. If more than one set of initial values is needed, add an Initial Values node from the Physics toolbar.
Boundary Selection
When the Initial Values node is added manually in the Heat Transfer in Shells interface or under the Thin Layer, Thin Film, or Fracture node, select the Restrict to layered boundaries check box to make the node applicable only if a layered material is defined on the boundary. If a layered material (Material with Layer thickness specified, Single Layer Material, Layered Material Link, or Layered Material Stack) is available, its name is then displayed beside the boundary index (for example, slmat1), otherwise the boundary is marked as not applicable.
When Initial Values is the default node of the Heat Transfer in Shells interface, or the default subnode of the Thin Layer, Thin Film, or Fracture node, it is applied on all the boundaries where the parent node is applied, and neither the boundary selection nor the Restrict to layered boundaries check box are editable.
Note that when the Shell type is Nonlayered shell in the Shells Properties section of the parent interface or node, the Restrict to layered boundaries check box is not editable.
Shell Properties
Different settings are available, depending on the settings in the Shell Properties section of the parent interface or node, and whether Initial Values is the default node or was added manually:
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When the Shell type is Layered shell in the Shells Properties section of the parent interface or node, the same layered material is used in the Initial Values node, but you can limit the contribution to individually selected layers by clearing the Use all layers check box, when this is not the default Initial Values node. For a given Layered Material Link or Layered Material Stack, you get access to a list of check boxes for the selection of the individual layers.
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When the Shell type is Nonlayered shell in the Shells Properties section of the parent interface or node, the Thickness is taken From physics interface or From parent feature in the Initial Values node. This option is not editable when Initial Values is the default node or subnode, but you can change to User defined and override the parent setting with a specific value or expression for Lth when the node was added manually.
You can visualize the selected layered materials and layers in each layered material by clicking the Layer Cross Section Preview and Layer 3D Preview buttons.
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For a general description of layer and interface selections, see Layer and Interface Selection Tools.
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You can provide material parameters with a through-thickness variation by using expressions containing the extra dimension coordinate as described in Using the Extra Dimension Coordinates.
The desired selection for the node may correspond to boundaries with different layered materials.
See Layered Material, Layered Material Link, Layered Material Stack, Layered Material Link (Subnode), and Single Layer Materials in the COMSOL Multiphysics Reference Manual.
Initial Values
For User defined, enter a value or expression for the initial value of the Temperature T. The default is approximately room temperature, 293.15 K (20º C). Else, select an Ambient temperature defined in an Ambient Properties node under Definitions.
When Initial Values is added as a subnode of Thin Layer, Thin Film, or Fracture node with Layer type set as Thermally thick approximation, it is applicable only on exterior boundaries and defines the initial temperature on the outer side of the thin structure. Note that the initial temperature of the inner side of the thin structure is always defined from the initial condition of the adjacent domains.
When Initial Values is added as a subnode of Thin Layer, Thin Film, or Fracture node with Layer type set as Thermally thick approximation or General, an additional option, From adjacent domains, is available. When it is selected, the initial temperature of the layer is uniform through the thickness and is equal to the average value of initial temperature in the adjacent domains. Note that this option is not available when the Initial Values feature is added in the Heat Transfer in Shells interface.
Theory for Heat Transfer in Thin Structures
Disk-Stack Heat Sink: Application Library path Heat_Transfer_Module/Thermal_Contact_and_Friction/disk_stack_heat_sink
Location in User Interface
Context Menus
Heat Transfer in Solids>Thin Layer>Initial Values
Heat Transfer in Solids>Thin Film>Initial Values
Heat Transfer in Solids>Fracture>Initial Values
Heat Transfer in Shells>Initial Values
Heat Transfer in Films>Initial Values
Heat Transfer in Fractures>Initial Values
Ribbon
Physics tab with Thin Layer selected in the model tree:
Attributes>Initial Values
Physics tab with Heat Transfer in Shells selected:
Boundaries>Heat Transfer in Shells>Initial Values