MANUAL Fluent 5

Volume of Fluid : Two Phases Flow

The aim of this version is to describe in more details the way to use the Volume of Fluid Model with Fluent.

__First Steps :__

Let's view the definition of the Operating conditions : **Define ->Operating
Conditions **:

In our case, the study was axisymmetric (**Define->Model->Solver**
and click **2D-Axisymmetric**), and Fluent accepts only an axis oriented
as the X-axis, that's why the Gravitational Acceleration is on X. When
doing an axisymmetric study, you have to define your **axis**, and if
your mesh has been made with PRE-BFC (which does not have axis zone), you
have to change your symmetry boundary condition into an axis (**Define->Boundary
Conditions**).

Note that you have also to click **Specified Operating Density.**

Our study is to compute a bubble of air in the gravity champ in a column
of water. So to enable the surface tension, you have to specified it in
the Multiphase Model Panel (cf Version 1 : **Define->Model->Multiphase
Model**) :

You can test the different VOF Scheme, but for our study the **Geo-Reconstruct**
one was recommended.

You can also try to **Solve VOF Every Iteration**, but it is only
recommended if under-relaxation factors are well set.

Then you have to specify the solution's parameters **Solve->Control->Solution**
:

__Defining a Bubble :__

As it is explain in the Version 1 of the VOF with
Fluent Manuel, you have to **Adapt->Region**, click **circle**, choose
center coordinates and the radius of your bubble :

Then click on **Mark**, on **Manage... ->Display** if you want
to see cells to be adapted, and on **Adapt**. Repeat the sequence **Mark/Adapt**,
until your bubble is a circle (you can see it with **Manage...->Display**,
__after a Mark action__). Here is the bubble obtain after some

Then you can follow the Version 1's explaination to initialize the two phases.