Setting Boundary Conditions and Values

The geometry used for this tutorial has six boundaries, four of which will have no-slip wall conditions assigned to them. The remaining two boundaries will be assigned pressure boundary conditions.

Open the Regions node, then right-click the Default_Fluid 2 node and select Rename...

Enter the name Fluid and click OK.

Open the Fluid > Boundaries node, then use the <Ctrl><Click> method to select the Middle, Left, Right and Bottom nodes. These are the four wall boundaries.

In the Properties window, select Type Wall.

Using <Ctrl><Click> again, select the TopLeft and TopRight nodes. These are the two pressure boundaries. In the Properties window, select Pressure Outlet as the boundary Type.

The default conditions are suitable for the wall boundaries but those for the pressure boundaries must be reset.

Within the TopLeft node, select the Physics Values > Turbulence Intensity > Constant node.

Set the Value property to 0.

Select the Turbulent Viscosity Ratio > Constant node.

Change the Value property to 0.

Finally, select the Volume Fraction > Constant node.

In the Properties window, click on the Value box to open the Constant - Value dialog.

Change the H2O value to 1.0

Leave the Air value as 0.0 and click OK.

This in effect enforces the condition that only water may enter the solution domain through that boundary.

The conditions for the TopRight boundary are identical to those for the TopLeft boundary, except that the water and air volume fractions are reversed. You could specify these boundary conditions as described above but, in this case, it is more convenient to copy the boundary conditions from the TopLeft to the TopRight boundary and then amend them.

Right-click the TopLeft node and select Copy.

Right-click on the TopRight node and select Paste.

Select the TopRight > Physics Values > Volume Fraction > Constant node.

In the Properties window, click on the Value box to open the Constant - Value dialog and then change the H2O value to 0.0 and the Air value to 1.0

This, in effect, enforces the condition that only air may enter the solution domain through that boundary.