Expanding the Cylinder

The same exercise can be repeated to model an expansion of the cylinder instead of a contraction. A displacement is specified at the wall boundary instead of a grid velocity.

  1. Select File > Save As and save the simulation with a filename of expansion.sim.
  2. Create a field function for the cylinder wall displacement with respect to the local cylindrical coordinate system:
    1. Right-click Automation > Field Functions and select New > Vector.
    2. Rename the vector field function to Cylinder Wall Displacement.
    3. Select the Cylinder Wall Displacement node and set the following properties:
      Property Setting
      Function Name CylinderWallDisplacement
      Dimensions Length
      Definition [(($$Position("Cylindrical 1")[2] < 2) ? 0.00625*$$Position("Cylindrical 1")[2] : 0.00625*(4-$$Position("Cylindrical 1")[2])), 0, 0]
The morpher conditions on the cylinder wall must be modified to use the new field function.
  1. Edit the Regions > Fluid > Boundaries > Wall node and set the following properties:
    Node Property Setting
    Physics Conditions
    Morpher Specification Specification Displacement
    Morpher Displacement Specification Specification Coordinate Offset
    Physics Values
    Coordinate Offset Method Field Function
    Vector Function Cylinder Wall Displacement
    Coordinate System Laboratory->Cylindrical 1
This completes the changes necessary for the expansion simulation.
  1. Select Solution > Clear Solution from the menu bar and click OK.
  2. Proceed to initialize and run the simulation as before using either the Solution > Run option or the (Run) button on the toolbar.
At the end of this second simulation:
  1. Click the Cylinder Wall tab at the top of the Graphics window.
  2. Use the mouse buttons to zoom out and position the part to obtain a view similar to that shown below.