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Vignesh V July 16, 2012 03:36

UDF starter

I'm trying to write my own UDF. I'm not getting anything from the FLUENT user guide.

Someone please help me with some example. How could i proceed in writing my own UDF.

flotus1 July 16, 2012 06:22

Tell us what you want to achieve with the UDF.
Then we can be a little more specific with the guidance we provide.

Vignesh V July 16, 2012 08:42


I'm new to UDF.

I'm trying to simulate a moving wall over a fluid.

Can u help me.

flotus1 July 16, 2012 08:56

The possibilities with UDFs are nearly infinite.
So is the range of complexity of UDFs.

Before you start writing a UDF, you should know what it is supposed to do.

Zzz_Mmm July 16, 2012 12:25

New question of dynamic mesh-udf
i want to use dynamic mesh to simulate a motion of a microorganism.i have understood that i have to write a UDF to define a motion of microorganism for fluent.i have 6 pictures(including data of positions) of microorganism in one cycle of its swimming these are my questions:
1- what my program suppose to do?(i am actually a little confused about it)
2- Do i have to interpolate to find the position of nodes through the time?
3-Do i need to calculate the velocity and acceleration of nodes too?(i only have data for positions)
4-which marcos should i use?
i have read the UDF manual but i didnt get whole of it.I would be thankful for any help from you?

Vignesh V July 17, 2012 01:02

Let us take an example of landing of aircraft(from certain height till its completely lands).

Is it need to define a UDF . If yes how to start.

I tell you again I'm new to UDF.

So, It would be helpful if you help in some basics steps how to write a UDF.

flotus1 July 17, 2012 02:27

I feel like we are speaking different languages here.
The landing of an aircraft provides about a trillion possibilities for the use of UDFs. Since the setup of the simulation is not even defined, I could only guess what the application of a UDF in this context could be.

The range is from setting a time-variant density ot the fluid to defining the movement of the landing flaps.
I am very sorry, but I can't provide any guidance about a topic that is totally vague.

Vignesh V July 17, 2012 05:36


Just tell me how to write a time dependent B.C's using UDF.

The problem is like flow of a water in a tank.

mvee August 4, 2012 05:17

Hi Vignesh

Read DEFINE_PROFILE macro. One UDF for already written for spatial variation of velocity for the flow over aerofoil. In this profile make some modifications like - first call and specify the real time as time variable 't' and change the equation of your kind with time variable 't'.

best wishes

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