# VOF wave getting damped.

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September 11, 2013, 07:07
VOF wave getting damped.
#1
Member

Arun Krishnan.L.H
Join Date: Jan 2013
Posts: 74
Rep Power: 4
Dear All,

I am going to work on wave interaction on ships and the dynamic forces for various cases. Just to get the modelling and meshing right for VOF wave and to what comes out of the software for a user defined wave, I am simulating first order waves in a rectangular domain.

The domain is 75m(x), 10m(y which is the direction of wave height), 1m(z direction). The free surface is initialized so that the domain is equally divided. The coordinate of y axis of free surface is 0.

I have defined a wave of length 5 mts, current/wind velocity 1.5 m/s, amp 0.1 mts. The mesh sizes on the free surface is refined using a block of height 0.3 m. The x and z refinement are wavelength/80 and y axis is amp/20. Time step is wave period (2.4*80). I have run the simulation using 50 and 70 inner iterations but the nature of the pressure plot seems to be that of a damped oscillation. Though the waves are not becoming completely flat , which was an issue i had before, it gets damped a little. The point on water level of the wave is 0,0,0. The distance from the wave to outlet is 50mts.

I have also changed the VOF relaxation from 0.9 to 0.5 but there is no change. Can anyone please guide me regarding what is going wrong or what other parameter i could change. I am running unsteady, inviscid model and 1st order solver.

Thanks
Regards
Arun
Attached Images
 vof initial.jpg (9.5 KB, 57 views) vof after 4 sec.jpg (10.3 KB, 55 views)

December 18, 2013, 09:34
#2
New Member

saeed barzegar
Join Date: Feb 2012
Posts: 2
Rep Power: 0
Dear Arun

I had a same problem. I suppose, you are working on old version of fluent? if it is true, you can follow another simple way (by new version of fluent (in ANSYS 13 or 13))
in ANSYS13-fluent, there are options for modeling wave (Airy, stocks,...) and free surface, but it takes times to realize. however, in this way you can simulate completely your problem.
my firs your problem was like "picture 1111" (likes your problem) and my result after modeling in new version of fluent is like "picture 2222" (that wave does not damp)

Also this link can help you for modeling wave in ansys-fluent: step by step for VOF modeling

I hope my suggestion will be helpful.
Attached Images
 1111.jpg (38.6 KB, 39 views) 2222.png (3.8 KB, 36 views)

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