Setting Initial Conditions

The initial condition for the spatial distribution of the two primary fluids in the continuum is that we only have water in the left-hand chamber and only air in the right-hand chamber and channel. A convenient way of specifying such a distribution is by creating and using field functions.

Select the Initial Conditions > Volume Fraction node.

In the Properties window, change the Method property to Composite

Select the Composite > Air node and change its Method property to Field Function

Open the Tools node at the bottom of the tree.

Right-click on the Field Functions node and select New Function

Right-click on the User Field Function 1 node and rename it Initial Distribution (Air)

In the Properties window, click on the Definition box to open the custom editor. In the editor window, enter the following syntax:

($$Position[0] >= -0.001) ? 1 : 0

Click OK to exit the editor.

Return to the Air node, open it and select the Field Function node beneath it.

Select Initial Distribution (Air) as the Scalar Function property.

Repeat the steps outlined above to specify the initial distribution of the H2O phase using a second field function named Initial Distribution (H2O) with the following definition:

($$Position[0] >= -0.001) ? 0 : 1

Since these two field functions are the inverse of each other, the water vapor concentration will be zero everywhere. This is appropriate for the case in hand as there is no cavitation in the stationary fluids.