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-   -   Problem Concerning free surface wave simulation (https://www.cfd-online.com/Forums/star-ccm/85098-problem-concerning-free-surface-wave-simulation.html)

 michaels February 17, 2011 08:47

Problem Concerning free surface wave simulation

Hi Everyone,

I got a problem concerning first order VOF waves in STAR CCM+.
Iīve created a plot for the free surface elevation, saved pictures after every time step and ticking through the pictures i recognized that the waves travel up and down as a group. They keep their form and donīt break or something, they just travel up and down periodically.
Any ideas why thatīs the case? Could it be a problem due to false BCīs?
My BCīs are velocity inlet where the waves enter, pressure outlet where they exit, both with field functions for e.g. hydrostatic pressure.
the sides are symmetry planes, the bottom and top also velocity inlets. I also tried bottom as wall and top as symmetry plane and both as symmetry plane which made no difference.

Another problem is that thereīs a reversed flow at the outlet boundary, which doesnīt seem to affect the waves, since they donīt pile up or something. Does a reversed flow mean ther is something false?

Which BC's would you use?

Regards

Michael

 Vinicius February 24, 2011 14:19

Are you simulationg just the waves, without any body inside?

If you are expecting the waves breaking, you must use 5th order waves. the first order are a poor approximation and are not adequate for this.

Regards,

 michaels February 25, 2011 03:18

the first trials are just the waves without any body...the aim is to monitor forces/pressure on a floating body later on. my wavelength is 1.72m and the amplitude 0.0565m.
would you use any kind of current or wind properties to eliminate the reversed flow output?

 Vinicius February 25, 2011 08:28

You should user velocity inlet in all your external boundaries, except in the outlet. You can also use the wave damping to avoid the waves reflect in the outlet boundary...

Take a look at the tutorials in the training guide.

Regards

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