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help request about wave moeling in free surface?

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Old   March 4, 2016, 12:20
Question help request about wave moeling in free surface?
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hamidi
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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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Old   March 5, 2016, 06:03
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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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Old   March 5, 2016, 11:06
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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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Old   March 6, 2016, 18:25
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I listed two options - there are others. You use whatever you think will model your flow.
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Old   March 7, 2016, 07:05
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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 14:12.
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Old   March 7, 2016, 17:22
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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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Old   March 8, 2016, 12:02
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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
Attached Images
File Type: jpg 2016-03-08_183905.jpg (60.4 KB, 10 views)
File Type: jpg 2.jpg (47.6 KB, 11 views)
File Type: jpg 3.jpg (47.1 KB, 10 views)
File Type: jpg 2016-03-08_193447.jpg (37.2 KB, 11 views)
Attached Files
File Type: txt wave.problem.txt (6.2 KB, 4 views)

Last edited by hamidciv; March 8, 2016 at 15:51.
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Old   March 8, 2016, 18:49
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Quote:
What could be because of decreasing depth of water?
You are not conserving volume fraction. You need to converge tighter. Also consider using the coupled volume fraction solver.

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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Old   March 10, 2016, 12:30
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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
Attached Images
File Type: jpg 1-wave.jpg (56.9 KB, 12 views)
File Type: jpg 2-wave.jpg (46.0 KB, 9 views)
File Type: jpg 3-wave.jpg (77.1 KB, 10 views)

Last edited by hamidciv; March 13, 2016 at 03:12.
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Old   March 10, 2016, 18:16
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Please attach your CCL.
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Old   March 11, 2016, 02:52
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thank you for your time dear glenn.

Last edited by hamidciv; March 11, 2016 at 12:00.
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Old   March 11, 2016, 03:12
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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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Old   March 11, 2016, 03:21
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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 04:26.
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Old   March 11, 2016, 06:10
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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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Old   March 11, 2016, 14:05
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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
Attached Images
File Type: jpg 2016-03-11_212416.jpg (56.1 KB, 8 views)
File Type: jpg 2016-03-11_212432.jpg (53.4 KB, 9 views)
File Type: jpg 2016-03-11_212442.jpg (52.6 KB, 8 views)
File Type: jpg 2016-03-11_212516.jpg (48.0 KB, 10 views)
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