Creating Surface Heat Fluxes
Surface heat fluxes represent uniform scalar heat fluxes applied to surface geometries.
Surface heat fluxes can be applied only in heat transfer steps.
The magnitude of a surface heat flux can vary with time during a step according to an amplitude definition (see Amplitudes for more information on defining amplitudes).
You can prescribe the time variation of the magnitude of a surface heat flux in a user subroutine, which is sometimes preferable when the time history of the magnitude is complex. You can also apply knowledgeware techniques to control the value of a surface heat flux (for more information, see Applying Knowledgeware).
You can import heat flux data into a surface heat flux definition from a Microsoft Excel spreadsheet (.xls*) or a text file (.txt). The imported heat flux data must satisfy the following criteria:
The data must be arranged in four columns in the following order: X-coordinate, Y-coordinate, Z-coordinate, and heat flux value.
The data must include a header row in which the dimensional data are provided in parentheses. Surface heat flux data can be provided without dimensions. The following sample header row provides one example of proper header row syntax:
X(mm) Y(mm) Z(mm) Heat flux()
The actual heat flux values created from imported data will be the product of the dimensionless heat flux values multiplied by the value you provide for the Magnitude of the initial temperature. For example, if your imported data specify a dimensionless value of 10 at the location (0, 0, 0) and you specify a value of 20W_m2 for the surface heat flux object, the surface heat flux at that location will be 200W/m2 for the analysis.
Surface heat fluxes can be applied to surface or face supports or to a surface group.
This task shows you how to create a surface heat flux on geometry.
Click the Surface Heat Flux icon
.The Surface Heat Flux dialog box appears, and a Surface Heat Flux object appears in the specification tree under the Loads objects set for the current step.
You can change the identifier of the load by editing the Name field.
Select the geometry support (a surface). Any selectable geometry is highlighted when you pass the cursor over it. You can select several supports to apply the load to all supports simultaneously. You can also select a surface group.
The Supports field is updated to reflect your selection. A temporary symbol will appear at the supports to indicate zero values until you apply a nonzero load.
Enter a value for the surface heat flux Magnitude.
Right-click on the surface heat flux Magnitude field to add knowledgeware controls (for more information, see Applying Knowledgeware).
To import and incorporate mappings for heat flux data into the surface heat flux definition, perform the following steps:
Toggle on Data mapping, then click the ... button.
The Data Mapping dialog box appears.
Click Browse, then select the spreadsheet or text file from which you want to import temperature data.
Once you select a file, you can display the imported data in tabular form in the Imported Table dialog box by clicking Show.
If desired, toggle on Display Bounding Box to display a three-dimensional box incorporating the minimum and maximum values from the imported table. The bounding box enables you to confirm that the support you select lies completely within the space dictated by the imported data; if a portion of the support is outside this box, an error will be returned during the analysis.
Click OK to close the Data Mapping dialog box.
Click More to access additional surface heat flux options.
Toggle on Selected amplitude, and select an amplitude from the specification tree to define a nondefault time variation for the surface heat flux.
If you do not specify an amplitude, Abaqus applies the reference magnitude based on the Default load variation with time option that you selected when you created the step. Abaqus either applies the reference magnitude linearly over the step (Ramp) or applies it immediately at the beginning of the step and subsequently holds it constant (Instantaneous).
See About Prescribed Conditions in the Abaqus Prescribed Conditions Guide for more information.
Toggle on Apply user subroutine to define a nonuniform variation of the surface heat flux magnitude throughout the step in user subroutine DFLUX. For more information, see Using User Subroutines and DFLUX in the Abaqus User Subroutines Guide.
Click OK in the Surface Heat Flux dialog box.
Symbols representing the applied heat flux are displayed on the geometry.