Boundary Conditions

In tutorial HX-1022 you learned how to create mesh for the solid profiles. This tutorial is a followup for HX-1022.

The tutorial starts with a meshed model and will teach you how to manually set up boundary conditions. You will set up four types of boundary conditions for this model - inlet, solid wall, free surface and exit.

The model files for this tutorial are located in the file mfs-1.zip in the subdirectory \hx\MetalExtrusion\HX_1154. See Accessing Model Files.

To work on this tutorial, it is recommended that you copy this folder to your local hard drive where you store your HyperXtrude data, for example, “C:\Users\HyperXtrude\” on a Windows machine. This will enable you to edit and modify these files without affecting the original data. In addition, it is best to keep the data on a local disk attached to the machine to improve the I/O performance of the software.

The files used in this tutorial as are follows:

•	Tutorial file - you will start from this file

– HX_1154.hm

1.	From the Start menu select: All Programs > Altair > HyperXtrude to launch the HyperXtrude User Interface. The User Profiles window appears with Manufacturing Solutions as the default application and HyperXtrude selected.

user_profile_pp

2.	Select Polymer_Processing from the drop down menu of HyperXtrude.

Click OK.

1.	From the File menu, click Open.

2.	Browse to the file HX_1154.hm. This file contains the meshed solid geometry and default unit selection.

3.	Click Open.

4.	Inspect the model. It has seven components with solids. These are InletManifold, Manifold1-5, and Land. The remaining components have 3D elements corresponding to these geometry components. InletManifold3D is the entry point for the polymer melt and Profile3D is the exit point.

HX_1154_01

1.	On the Utility menu, click Select Units.

2.	Set the Unit System to Metric and set the options as shown in the figure below.

hx_1154_assign_units

Click OK.

Note: Measure dimensions of the model by pressing <F4> on the key board to get an idea about the units of the model.

The length unit of the present model is ‘mm’.

1.	In the Utility menu, click Material Data to open the Select and Assign Material from Database dialog.

2.	In the dialog, expand the Polymers folder, then PVC. Select and load the material PVC_Generic.

3.	Click Add. The entry moves into the Selected materials column.

4.	Under Selected materials, right click on the loaded material and select Assign Material.

HX_1154_04

5.	In the bottom panel, assign the material to all 3D components and click Update. Click Close to close the dialog.

HX_1154_05

You will setup four types of boundary conditions for this model

•

Inlet

•	Solid Wall

•	Free surface

•

Exit

This is a simplified setup. If you use the wizard, it will create these same boundaries under separate names corresponding to each 3D component. However, the principle applied is the same.

1.	On the Utility menu, under BCs:, click on Create/Edit.

2.	In the Boundary Conditions dialog, click BCs.

3.	In the Name: field, enter Inlet.

4.	For the Type: field, select Inflow.

5.	In the Material: field, select PVC_Generic (Polymer).

6.	Select a color.

7.	Click Create.

8.	Enter 5 mm/sec in the ZVelocity field.

9.	Make sure that Temperature is selected. Enter 150 degree centigrade in the temperature field.

10.	Click Update after you have modified the velocity and temperature data. This is needed to update the BC load cards. If this step is missed, data will not be updated when you close the dialog.

11.	Click on Create Faces. This will allow you to select face elements for the Inlet BC profile.

12.	Click one element on the inlet side of InletManifold3D and click proceed. This will create shell elements representing inflow boundary conditions.

HX_1154_06

1.	In the Boundary Conditions dialog, click BCs again.

2.	In the Name: field, enter wall.

3.	For the Type: field, select SolidWall.

4.	In the Material: field, select PVC_Generic (Polymer).

5.	Select a color.

6.	Click Create.

7.	In the next panel, select Stick for Friction Model and set all three components (X, Y, and Z) of Velocity to 0.

8.	Set the Heat transfer type field to Convection.

9.	Enter 15 for Conv. coefficient: field.

10.	Enter 40 for Conv. temperature: field.

11.	Click Create Faces. This allows you to select face elements on the exit side of the profile.

12.	Select a few elements on the side of all the 3D components, except Profile3D, and click proceed. This will create shell elements representing solid wall boundary conditions. This BC can be split into separate BCs for each of the manifolds, which is described in the next tutorial.

Boundary faces are captured based on break angle, hence it is important that you should select enough elements to ensure the entire side surface is captured for the SolidWall BC. In this model there are elements in sharp corners between manifolds, and you have to select them to get all BCs captured on all boundary surfaces.

HX_1154_07

HX_1154_07b

1.	In the Boundary Conditions dialog, click BCs again.

2.	In the Name: field, enter freesurface.

3.	For the Type: field, select FreeSurface.

4.	In the Material: field, select PVC_Generic (Polymer).

5.	Select a color.

6.	Click Create.

7.	Set the Heat transfer type field to Convection.

8.	Enter 15 for Conv. coefficient: field.

9.	Enter 40 for Conv. temperature: field and click Update.

10.	Click on Create Faces. This will allow you to select face elements on the exit side of the Profile3D.

11.

Click on a few elements around the circumference (to overcome break angles) on the sides of all of the Profile3D blocks and click proceed. This will create shell elements representing Free Surface boundary conditions. This BC can be split into separate BCs for each of the profile blocks, which is described in the next chapter.

Another option would be to increase the break angle.

HX_1154_08

1.	In the Boundary Conditions dialog, click BCs again.

2.	In the Name: field, enter exit.

3.	For the Type: field, select Outflow.

4.	In the Material: field, select PVC_Generic (Polymer).

5.	Select a color.

6.	Click Create.

7.	Check the box for Pressure and click Update.

8.	Click Create Faces. This allows you to select face elements on the exit side of the profile.

9.	Select a few elements on the side of all four profile blocks and click proceed. This will create shell elements representing outflow boundary conditions.

Boundary faces are captured based on break angle, hence it is important that you should select enough elements to ensure the entire side surface is captured for the Exit BC.

HX_1154_09

Only one of the four profile blocks is shown

10.	Click Close to close the dialog.

Note:

•	A load collector is created for each BC face which can then be card edited from the Model browser to see the BC definition.

•	Click on Update in the Utility menu dialog if you make any changes to the selection.

11.	In the Utility menu, click on Undefined. The Success window should appear.

hx_1154_checkundefinedbc_success

12.	In the Utility menu, click Duplicate. The Success window should appear.

hx_1154_checkduplicatebc_success

13.	If any of the above checks fail, please review the boundary faces and correct if necessary.

1.	From the Utility menu, click Parameters.

2.	In the Sessions tab, enter the Job Description as bc_setup.

3.	Enter a Job/Model Name (e.g. HX_1154), then click Update.

4.	In the Polymer Processing tab, select Yes for Calculate Free Surface.

5.	Select Off for the Mesh Update Flag.

6.	Make sure that selection is No for the Isothermal Flow Yes/No option, then click Update.

7.	On the User Commands tab, under Footer data, type solve and exit below interactive, then click Update.

8.	Click on Close.

1.	On the Utility menu, click Summary.

2.	Click on the Element Statistics tab on the Model Summary window.

3.	Click Show Element Quality.

hx_1154_modelsummary

4.	Inspect the values of element aspect ratio, min angle, max angle and Jacobian; it is OK if few elements do not pass the quality criterion as listed in the table.

For example, the Model Summary table checks if the element’s minimum angle is greater than 10 and if a small percentage of elements have a minimum angle less that 10, it should be OK. The requirement that the aspect ratio should be less than 8 is a stringent one and for hexahedral/prism elements, aspect ratios up to 20 in some regions should be fine. HX solver can handle a small percentage of elements with poor quality and hence, the quality checks in this table should be seen as a broader guideline and not as a stringent requirement.

5.	Click Close to close the dialog.

1.	On the Utility menu, under Export click on Export/Launch Solver.

2.	Use the browser to select a path and name for the files to be exported.

3.	Make a selection in the Launch Solver field. There are three options:

•	No: This is the default option. With this option only the solver files namely, GRF and TCL files will be exported. The file can later be used to run HX-Polymer analysis on ecompute or on a different machine

•	Interactive: This option will allow to control the job interactively through a GUI as shown below

•	Batch: Solve the job in batch mode.

HX_1154_10

4.	Click Export. This will generate the solver input files, HX_1154_FINAl.hx and HX_1154_FINAL.grf.

Return to Polymer Processing Tutorials

HX-1154: Boundary Conditions

HX-1154: Boundary Conditions

HX-1154: Boundary Conditions