# Problem Concerning free surface wave simulation

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 February 17, 2011, 07:47 Problem Concerning free surface wave simulation #1 New Member   Join Date: Feb 2011 Posts: 13 Rep Power: 14 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? Iīd appreciate any advise. Regards Michael Bulava likes this. Last edited by michaels; February 21, 2011 at 06:46.

 February 24, 2011, 13:19 #2 Member   Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 16 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,

 February 25, 2011, 02:18 #3 New Member   Join Date: Feb 2011 Posts: 13 Rep Power: 14 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?

 February 25, 2011, 07:28 #4 Member   Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 16 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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