Weird velocity at the air-water interface in olafoam
 

Hi, foamers. I'm using olafoam to simulate waves above a structure(a simple mound) like below.

http://i1180.photobucket.com/albums/...pswyipvmgi.png

As you can see, there exist some weird huge velocities at the start point and end point of the structure even though waves didn't approach the structure yet.

The surface is air-water interface(alpha.water=0.5) and the structure was inserted by using snappyHexMesh.

Can anyone explain to me why that some noises exist?
Thank you in advance.!

Hi Jung Hoo,

what you see there are spurious velocities (look for it in the forum) when the free surface reaches a non-conformal mesh section (i.e. change in refine level).

There is usually no solution, so what I tend to do is to refine the cells in which the free surface is going to be during the whole simulation to the same level beforehand. Another alternative is to use dynamic mesh refinement.

Before that, check whether this effect influences your results. It sometimes only decreases dt due to the large velocities and you may learn to live with it...

Best,

Pablo

Thank you for your fast reply. Now I can understand why the spurious velocities exist where the mesh refine level changes.

Thank you for your help!