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help request about wave moeling in free surface? |
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March 4, 2016, 11:20 |
help request about wave moeling in free surface?
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#1 |
Senior Member
Hydreaulic structures
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hi dear all
i want generate waves in free surface in my model, i read tutorial of cfx, but unfortunately, i dont find any matter That is associated with the wave modeling, Also I have also read in this forum, but dont solve my problem. how i can generate wave in free surface? (Is there a different methods to do it?) please, if exist refterence about this, introduce me. thanks a lot for any comment for help me. best regards hamid |
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March 5, 2016, 05:03 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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You can use moving mesh to cause a wave. The tutorial example of the rigid body buoy simulation does this.
Or you can put a disturbance in the inlet. Any disturbance will generate waves, but if you want waves which look like waves you see in the ocean you will need to use a better model, such as this: http://www.geoexpro.com/articles/201...d-seismic-data |
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March 5, 2016, 10:06 |
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#3 |
Senior Member
Hydreaulic structures
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hi dear glenn
yes, as your mentioned, my goal is simulating ocean waves, based on your link, whether in fact, i should define u,v as initial conditions in my model? i appriciate you for guide me. best regrads |
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March 6, 2016, 17:25 |
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#4 |
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Glenn Horrocks
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I listed two options - there are others. You use whatever you think will model your flow.
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March 7, 2016, 06:05 |
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#5 |
Senior Member
Hydreaulic structures
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dear glenn, thanks for spending time for me & others.
i used of u,v velocity in initial conditions, I just want to see movement of waves in my model in form Schematically, therefore i using of coarse mesh, my wave properties is: T=2s,wave height=0.7m, depth of water=4m,wave length=1m unfortunately, dont produce any wave on the water surface, what is cause it? i am new in wave modeling. i attached CEL in here, if your possible, please check it. thanks a lot for any comments best regards hamid Last edited by hamidciv; March 8, 2016 at 13:12. |
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March 7, 2016, 16:22 |
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#6 |
Super Moderator
Glenn Horrocks
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Location: Sydney, Australia
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Your w equation makes no sense. I presume it is the water volume fraction. It just defines a constant level - which is what you are seeing.
Have a look into the reference I sent you, and search for others. There are several ways to define free water waves. If this is too hard then just use moving mesh to move a boundary and generate waves that way. |
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March 8, 2016, 11:02 |
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#7 |
Senior Member
Hydreaulic structures
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hi dear glenn
as your mentioned, i define one constant level using of VF(air&water), based on your links that your sent, i defining uvel,vvel as inlet velocity and i put wvel equal to zero, for initial conditions, i using of VF, for boundary conditions, i definining inlet , outlet and others as wall. because My goal was only to see the movement of waves in forms approximately, my quality mesh is not good. length of my domain is :10 m, depth of water:4m, period:2s, wave length:7m , wave height:0.7m During the running of model, waves is dissipated and Continuously depth of water is reduced, What could be because of decreasing depth of water? i attached images of results in different timestep and ccl. if your possible, please guide me as always. with the best wishes hamid Last edited by hamidciv; March 8, 2016 at 14:51. |
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March 8, 2016, 17:49 |
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#8 | |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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Quote:
You don't seem to have adjusted any free surface modelling parameters. As I said previously, the defaults can usually be significantly improved. |
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March 10, 2016, 11:30 |
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#9 |
Senior Member
Hydreaulic structures
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hi dear glenn, thanks for reply.
I've been trying for modify of wave modeling based on your orders, also i read your posts forum in associate with the wave modeling, but unfortunately, until now, my problem is not solved. based on surface wave theory, i define u,v using of following equations that i attached images of them, then i setting u,v in inlet BC, in fluid values tab in inlet BC, i sitting VFwter=0 and VFair=1, for IC, i sitting air=airVF & water=waterVF i do know that my problem induced of wrong sitting of volume fraction ,But despite much effort, So far I dont success. if your possible, please help me, how do this? sorry, please explain a little more. thanks in advance hamid Last edited by hamidciv; March 13, 2016 at 02:12. |
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March 10, 2016, 17:16 |
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#10 |
Super Moderator
Glenn Horrocks
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Please attach your CCL.
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March 11, 2016, 01:52 |
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#11 |
Senior Member
Hydreaulic structures
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thank you for your time dear glenn.
Last edited by hamidciv; March 11, 2016 at 11:00. |
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March 11, 2016, 02:12 |
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#12 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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You have defined constant volume fractions over the entire inlet, outlet and opening boundaries. This is obviously causing your problem. You need to define the water height at the inlet and either define it at the outlet or use an outlet which does not require it to be defined.
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March 11, 2016, 02:21 |
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#13 |
Senior Member
Hydreaulic structures
Join Date: Sep 2012
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hi dear glenn
if I understand your mean correctly , i should define water height as VF in inlet,That wave can fluctuate and is not confined. at first, for outlet BC, i define it as outlet type, but unfortunately it get error and run stopped, therefore i define it as opening type, now, based on your advise, i considered it as wall type. wheteher i understanding your mean correctly? Thank you very much with the best wishes Last edited by hamidciv; March 11, 2016 at 03:26. |
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March 11, 2016, 05:10 |
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#14 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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At an inlet you specify the VF. You specified that it is all air, so that is why your inlet was wrong.
You should implement an outlet which matches what you are modelling. Obviously if you have a wall that means the VF level will look after itself - but it will reflect waves and that may not be want you want either. |
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March 11, 2016, 13:05 |
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#15 |
Senior Member
Hydreaulic structures
Join Date: Sep 2012
Posts: 283
Rep Power: 14 |
hi dear glenn, hope are you fine.
With your help, my problem that was caused by the wrong VF of the inlet BC were solved. i really appreciate your help, as your mentioned, Waves facing with wall and reflected. My goal is only schematic simulation of the waves and seeing them using cfx software. I wish you success hamid |
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