CFD Online Discussion Forums

CFD Online Discussion Forums (
-   Main CFD Forum (
-   -   Initialization of VOF (

Jennie November 13, 1999 14:01

Initialization of VOF
Hi! there,

My friend is simulating free-surface flow using Fluent v.5

(1) It is difficult to give the initial volume of fluid (VOF) using PATCH command since the shape of free surface is complex

(2) For using the user defined function. What's the command to give the initial values of VOF? Is it C_F(c,t)?

(3) For using a Profile file (with x,y,z,VOF in turn), we do not know how the x,z,z,vof are put into the profile file.

Could anyone help my friend? Otherwise, my frined will lose his job. Thanks.


Joern Beilke November 13, 1999 19:41

Re: Initialization of VOF
Hi Jenny,

For question 2 and 3 your friend should ask the Fluent-Support and/or read the manual.

So lets try to find an answer to Q1.

Just think how the things are working in reality? There the water is somwere and the air also. Then something happens which leads to a complex shape of the interface.

Thats what you basically have to do with the simulation. Choose a starting point where you know the distribution and start the calculation. Then the shape of the interface will develope over the time.

This sounds very easy but it is not!!!!

All the VOF stuff is still a bit new and on has to become familiar by starting with simple cases. So don't expect a fast solution. Also the computing time is remarkable, esp. if you have to include surface-tension effects.

Jennie November 14, 1999 12:00

Re: Initialization of VOF
Dear Joern,

Thanks for your message.

But sometimes, the initial distribution of VOF is complex, and can not be patched easily. Could you forward your suggestion?


Sung-Eun Kim November 16, 1999 12:18

Re: Initialization of VOF

If his job is in jeopardy, he should've contacted his support engineer at Fluent Inc. What a really bad publicity to us if he loses his job because of FLUENT code !

1. Can you tell me specifically what sort of initial condition he tries to specify ? Simple topography such as flat surfaces (coordinate surfaces e.g., z= h), rectangles, boxes, circles, and spheres can be easily patched using "Patch" facility in FLUENT 5. If he has to specify complex topography of the free surface, he should use UDF. But I wonder what kind of complex free surface shape he can possibly specify. 2. C_VOF(c,t) is the MACRO for volume-fraction 3. Please read the user's manual. The manual explains everything you need to know in much detail.

Jennie November 18, 1999 17:41

Dear Kim,

Thank you very much for your message. >.<

My friend already tried to use the Micro. He said,

The computed results is bad. The breakup of liquid column under surface tension was also simulated, but there is no difference between the results using 2D cartesian or cylindrical coordinates. Is it a internal bug of Fluent V. 5.02?

I have a source code for free surface flow.

Thank you again. >@<


All times are GMT -4. The time now is 06:31.