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 amin62gh June 1, 2010 01:30

Dynamic Mesh UDF question

Dear users,

I want to assign a movement to a rigid wall in order to generate wave. But problem is here, having no velocity function ( vel (time)) , how can I make the wall move with a time-history of displacement.

Best Regards,
Amin

 O.D.Y. June 1, 2010 03:45

Hi,

you can do it via DEFINE_CG_MOTION.
It can be used to give walls velocities w.r.t. to any functional relation to time.

The function is pretty well explained in the UDF User Guide including an example. And if you search for it in the forum you will find some examples of others.

cheers

 Randre June 1, 2010 10:48

Hi

If you want to simulate a flap-type wave maker (I suppose yes, regarding your description), I advise you to check the following paper (wow, was right in front of me at this moment :O) where are defined the flap displacement functions - For those, you need to write an UDF with the macro above (DEFINE_CG_MOTION):

Lal, Anant; CFD Simulation and Validation of Flap-Type Wave-Maker. World Academy of Science, Engineering and Technology vol. 46 pp 76-82, 2008

But you don't need to simulate the displacement of the flap in order to create waves in FLUENT. You can assign Velocity-Inlet BC to your wave-maker wall and input an UDF with the x and y wave velocities from the linear wave theory or stokes theory.

And it gets easier if you have the last version of FLUENT. go to
Define - Models - Multiphase - VOF - Open Channel Flow / Open Channel Wave BC (check them both), and then in wave maker wall: BC Velocity Inlet and input in FLUENT GUI your wave info.