Loads and Boundary Conditions

Thermal > Building A Model > Loads and Boundary Conditions

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''">XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''">

The Loads and Boundary Conditions form appears when the Loads⁄BCs toggle, located on the Patran main form, is chosen. The selections on this form will determine which Loads and Boundary Condition forms will appear, and ultimately, which Patran Thermal loads and boundary conditions will be created.

The following page gives an introduction to the Loads and Boundary Conditions forms, followed by details of the loads and boundary conditions supported by the Patran Thermal Solver.

Loads and Boundary Conditions Form

The Loads and Boundary Conditions form is used to create Patran Thermal loads and boundary conditions. For more information, see Loads and Boundary Conditions Form (p. 21) in the Patran Reference Manual.

The following table outlines the options when the Analysis Type is set to Thermal.


Object	Type	Option
• Temperature (PThermal)	• Nodal	• Fixed • Time Table • Coupled • Initial • Template
• Heating (PThermal)	• Element Uniform • Element Variable	• Flux, Fixed
	• Element Uniform	• Flux, Time Table • Flux, Temperature Table
	• Element Uniform • Element Variable	• Template, Fluxes • Template, Volumetric Heat
	• Nodal	• Template, Nodal Source
	• Element Variable	• Flux, Spatial Field (Time)
• Convection	• Element Uniform • Element Variable	• Fixed Coefficient
	• Element Uniform	• Time Table • Temperature Table
	• Element Uniform • Element Variable • Element Variable	• Template Convection • • Spatial Field (Time)
• Radiation	• Element Uniform • Element Variable	• Ambient Node
	• Element Uniform • Element Variable	• Gap Radiation •
	• Element Uniform	• Template ViewFactors
	• Element Uniform	• Spacecraft, STEP_TAS
• Pressure	• Nodal	• Fixed • Time Table • Initial • Template
• Mass Flow	• Nodal	• Fixed • Time Table • Initial • Template

The following specifies the defined variables which are used to specify the Boundary Condition ID. By using the variable name the specific ID can be assigned in a define statement and only needs changing at one location in any special PCL one may write using the defined boundary conditions.


Object	Option	LBC ID Variable Name
• Temperature (PThermal)	• Fixed • Time Table • Coupled • Initial • Template	• LBC_PTH_TEMP_TIME_TABL_ID • LBC_PTHERMAL_TEMP_FIXD_ID • LBC_PTHERMAL_TEMP_COUP_ID • LBC_PTHERMAL_TEMP_INIT_ID • LBC_PTHERMAL_TEMP_TMPL_ID
• Heating (PThermal)	• Flux, Fixed	• LBC_PTH_HEAT_FLUX_FIXD_ID
	• Flux, Time Table • Flux, Temperature Table	• LBC_PTH_HEAT_FLUX_TIME_TABL_ID • LBC_PTH_HEAT_FLUX_TEMP_TABL_ID
	• Template, Fluxes • Template, Volumetric Heat	• LBC_PTHERMAL_HEAT_TMPL_FLUX_ID • LBC_PTHERMAL_HEAT_TMPL_VOLH_ID
	• Template, Nodal Source	• LBC_PTHERMAL_HEAT_TMPL_NODS_ID
	• Flux, Spatial Field (Time)	• LBC_VAR_PTH_FIELD_NAME
• Convection	• Fixed Coefficient	• LBC_PTH_CONV_FIXD_ID
	• Time Table • Temperature Table	• LBC_PTH_CONV_TIME_TABL_ID • LBC_PTH_CONV_TEMP_TABL_ID
	• Template Convection	• LBC_PTHERMAL_CONV_TMPL_ID
	• Spatial Field (Time)	• LBC_VAR_PTH_FIELD_NAME
• Radiation	• Ambient Node • Gap Radiation • Template ViewFactors • Spacecraft, STEP_TAS	• LBC_PTH_RADI_AMBN_ID • LBC_PTHERMAL_RADI_GAP_ID • LBC_PTHERMAL_RADI_TMPL_ID • LBC_PTH_RADI_STAS_ID
• Pressure	• Fixed • Time Table • Initial • Template	• LBC_PTHERMAL_PRES_FIXD_ID • LBC_PTH_PRES_TIME_TABL_ID • LBC_PTHERMAL_PRES_TMPL_ID • LBC_PTHERMAL_PRES_INIT_ID
• Mass Flow	• Fixed • Time Table • Initial • Template	• LBC_PTHERMAL_MDOT_FIXD_ID • LBC_PTH_MDOT_TIME_TABL_ID • LBC_PTH_MDOT_GEN_FUNC_ID • LBC_PTHERMAL_MDOT_INIT_ID


LBC ID	LBC Load Type
• 51	• Temperature (PThermal)[Fixed]
• 52	• Temperature (PThermal)[Time Table]
• 54	• Temperature (PThermal)[Coupled]
• 55	• Temperature (PThermal)[Initial]
• 56	• Temperature (PThermal)[Template]
• 60	• Heating (PThermal)[]Flux, Fixed
• 61	• Heating (PThermal)[Flux, Time Table]
• 62	• Heating (PThermal)[Flux, Temperature Table]
• 67	• Heating (PThermal)[Template, Fluxes]
• 68	• Heating (PThermal)[Template, Volumetric Heat]
• 69	• Heating (PThermal)[Template, Nodal Source]
• 70	• Heating (PThermal)[Flux, Spatial Field(Time)]
• 101	• Convection (PThermal)[Fixed Coefficient]
• 102	• Convection (PThermal)[Time Table]
• 103	• Convection (PThermal)[Temperature Table]
• 105	• Convection (PThermal)[Template, Convection]
• 107	• Convection (PThermal)[Spatial Field(Time)]
• 109	• Radiation (PThermal)[Ambient Node]
• 110	• Radiation (PThermal)[Gap Radiation]
• 112	• Radiation (PThermal)[Template, View Factors]
• 113	• Radiation (PThermal)[Spacecraft, STEP_TAS]
• 116	• Pressure (PThermal)[Fixed]
• 117	• Pressure (PThermal)[Time Table]
• 119	• Pressure (PThermal)[Initial]
• 120	• Pressure (PThermal)[Template]
• 124	• Mass Flow Rate (PThermal)[Fixed]
• 125	• Mass Flow Rate (PThermal)[Time Table]
• 127	• Mass Flow Rate (PThermal)[Initial]
• 128	• Mass Flow Rate (PThermal)[Template]

The actual LBC IDs are defined in the following table.


Object	Option	LBC ID
• Temperature (PThermal)	• Fixed • Time Table • Coupled • Initial • Template	• 51 • 52 • 54 • 55 • 56
• Heating (PThermal)	• Flux, Fixed • Flux, Time Table • Flux, Temperature Table • Template, Fluxes • Template, Volumetric Heat • Template, Nodal Source • Flux, Spatial Field (Time)	• 60 • 61 • 62 • 67 • 68 • 69 • 70




• Convection	• Fixed Coefficient • Time Table • Temperature Table • Template Convection • Spatial Field (Time)	• 101 • 102 • 103 • 105 • 107



• Radiation	• Ambient Node • Gap Radiation • Template ViewFactors • Spacecraft, STEP_TAS	• 109 • 110 • 112 • 113
• Pressure	• Fixed • Time Table • Initial • Template	• 116 • 117 • 119 • 120
• Mass Flow	• Fixed • Time Table • Initial • Template	• 124 • 125 • 127 • 128

Input Data

This subordinate form appears when the Input Data button is selected and Static is the Load Case Type selection (the only Load Case selection currently supported). For Patran Thermal boundary conditions are not specified separately for steady state and transient conditions which are defined in the analysis form. Thus the distinction between static and dynamic load case has no meaning. The information contained on this form will vary according to the selected Object.

All boundary condition options which do not contain the word “Template” involve direct translation and the information is not written to the neutral file. All the boundary condition information is complete within the Patran model and does not require any supplementary information to complete the input to the solution module. However, all options which contain the word “Template” translate information passed through the neutral file and many case requires additional information which is defined through a template file. The actual translation is done external to Patran. This template file can be built independently or with the template builder available in the analysis menu.

Defined below is a typical form for Convection (PThermal) as the Object and Fixed Coefficient as the Option.

Spatial Fields

Select Application Region

All of the non-template convection options have two selection regions for determining where the convection boundary condition is to be applied (Application Region) and the corresponding fluid node (Coupling Region).

Time Table

Input Data form when Time Table option is selected.

Fixed Option

Following are the input forms for the convection template option.

Non Fixed Option

Gap Radiation

Gap Radiation is used for all radiation between entities is not strongly influence by view factor considerations.

General Radiation

General Radiation considerations are calculated with P/VIEWFACTOR. The boundary conditions are defined through enclosure IDs and template information. Each enclosure is treated as a separate entity but may have several boundary conditions associated with it. Each material is identified by its own Template ID and different surface characteristics can be further separated by different boundary conditions.

Template Definitions

For variable boundary conditions, Patran Thermal uses a pointer system called a Template ID to reference more data contained in an auxiliary file. This external file is named template.dat.apnd and is created using forms on the analysis menu or the system editor in the same directory level as the Patran database. When a job is submitted from Patran, the template.dat.apnd file (if it exists) will be appended to the template.dat file created automatically in the sub-directory with the Job Name.

In the current release of Patran Thermal, Template IDs are required for all boundary conditions with “Template” in the option name. The following table shows boundary condition data types, Template Name and applicable field types.


LBC	Type of Data	Template Required	Fields Referenced
• Temperature	• Constant or Spatial Field	•	•
• Temperature		• Time dependent	• MACRO (p. 697)	• Non-Spatial/General
• Heating	• Constant or Spatial Field	•	•
• Heating		• Time or Temperature	• MACRO (p. 697)	• Non-Spatial/General
• Convection	• Constant or Spatial Field	•	•
		• Time or Temperature	• CONV (p. 700) Note: Use Config 29	• Material Prop/General
		• Correlations Library	• CONV (p. 700)	• Material Prop/General
• Radiation	• Viewfactor code data	• VFAC (p. 702)	• Material Prop/General
		• TRASYS Preference	• VTRA (p. 706)	•
		• NEVADA Preference	• VNEV (p. 708)	•
• Pressure	• Constant or Spatial Field	•	•
• Pressure		• Time or Temperature	• MACRO (p. 697)	• Non-Spatial/General
• Mass Flow	• Constant or Spatial Field	•	•
• Mass Flow		• Time or Temperature	• MACRO (p. 697)	• Non-Spatial/General

Object Tables

On the input data form, there are areas where the load data values are defined. The data fields presented depend on the selected Object and Type. In some cases, the data fields also depend on the selected Target Element Type. These Object Tables list and define the various input data which pertain to a specific selected object:

Temperature (PThermal)


Object	Type	Option
Temperature	Nodal	Fixed


Input Data	Description
Temperature	Temperature (value or spatial field) that remains fixed in the analysis.


Object	Type	Option
Temperature	Nodal	Time Table


Input Data	Description
Name	Micro Function name that Table will be stored under in the general fields.
Description	Definition of Table.
Time Temperature	Data pairs which define a bounded linear table which specifies temperature as a function of time.


Object	Type	Option
Temperature	Nodal	Initial


Input Data	Description
Temperature	Initial temperature (value or spatial field). If the entire model has the same initial temperature, set the global value under Analysis/Solution_Parameters/Run control Parameters.


Object	Type	Option
Temperature	Nodal	Coupled


Input Data	Description
<No Input Data>	Usage: This option only uses Select Application Regions to define the primary application region and the companion region that will be thermally coupled. This option can be used to couple topologically non-congruent meshes, to model cyclical symmetry or to tie nodes in mixed 3D and axisymmetric models. The entities will be coupled based on a Selection order or Closest Approach, as chosen. To maintain accurate transient effects, the thermal capacitance of the node in the companion region will include the capacitance of the node in the primary application region.


Object	Type	Option
Temperature	Nodal	Template


Input Data	Description
Temperature	Scale factor on temperature returned from template evaluation.
Template ID	Positive template ID points into template.dat file.

Convection (PThermal)


Object	Type	Target	Option
Convection	Element Uniform Element Variable	1D, 2D, 3D	Template, Convection


Input Data	Description
Convection Coefficient	Convective heat transfer coefficient or a geometric property if template ID is used.
Convection Template ID	Positive integer, points convection template in template.dat file.
Fluid Node ID	The node ID to which the heat is convected.


Object	Type	Target	Option
Convection	Element Uniform Element Variable	1D, 2D, 3D Nodal,1D,2D,3D	Fixed Coefficient


Input Data	Description
Convection Coefficient	Heat transfer coefficient (constant or spatial field). Correlations library not allowed in this option. The corresponding area for convection will be based on application region 1 entities. This boundary condition is useful for connecting dissimilar meshes with thermal resistance in between or for tying a surface to a fluid stream. Convection between regions can be applied to 1D elements for 2D thermal or axisymmetric elements. Currently not supported for 1D elements in 3D space.


Note:	Filter must be the same (either Geometry or FEM) on both application regions.

Heat Flux


Object	Type	Target	Option
Heating	Element Uniform Element Variable	1D, 2D, 3D	Template, Fluxes


Input Data	Description
Heat Flux	Heat flux value or a scale factor if template ID is used.
Template ID	Positive integer, points heat macro in template.dat file.

Nodal Heat


Object	Type	Option
Heating	Nodal	Template, Nodal Source


Input Data	Description
Heat Source	Nodal heat source or a scale factor if template ID is used.
Template ID	Positive integer, points macro in template.dat file.

Volumetric Heat


Object	Type	Target	Option
Heating	Element Uniform Element Variable	1D, 2D, 3D	Template, Volumetric Heat


Input Data	Description
Heat Source	Volumetric heat source or scale factor if template ID is used.
Template ID	Positive integer, points macro in template.dat file.

Pressure


Object	Type	Option
Pressure	Nodal	Template, Fixed, Initial


Input Data	Description
Pressure	Nodal pressure or scale factor if template ID is used.
Template ID	Positive integer, points pmacro in template.dat file.

Mass Flow


Object	Type	Option
Mass Flow	Nodal	Template, Fixed, Initial


Input Data	Description
Mass Flow Rate	Nodal mass flow node or scale factor is template ID is used.
Template ID	Positive integer, points mmacro in template.dat file.

Radiation (PThermal)


Object	Type	Target	Option
Radiation (PThermal)	Element Uniform Element Variable	1D, 2D, 3D Nodal, 1D, 2D, 3D	Gap Radiation


Input Data	Description
Surface 1 Emissivity	Emissivity value or spatial field for application region 1.
Surface 2 Emissivity	Emissivity value or spatial field for companion region 2 (default = 1).
Form Factor	Viewfactor value applied to the radiation couplings (default = 1).


Note:	Filter must be the same (either Geometry or FEM) on both application regions.

Viewfactor


Object	Type	Target	Option
Radiation	Element Uniform	1D, 2D, 3D	Viewfactor


Input Data	Description
Enclosed ID	Enter radiation enclosure ID.
Template ID	Positive Integer points to VFAC, VTRA or VNEV data in template .dat file.