VOF waves breaking in my simulation

 Register Blogs Members List Search Today's Posts Mark Forums Read

 December 10, 2010, 12:23 VOF waves breaking in my simulation #1 New Member   Mehrdad Join Date: Apr 2009 Posts: 11 Rep Power: 10 I am trying to generate first order VOF waves with amplitude of 0.405m and wave period of 2.5 s. After few iterations waves start to break. Is it because of incorrect BC or large time step or.... I am using t=0.003 s and boundary conditions are velocity inlet at left hand side and pressure outlet at right hand side and symmetry plane on two sides of simulation. Any help in the regard would be highly appreciated. Thanks.

 December 11, 2010, 18:15 #2 Member   Naimish Harpal (MS Aerospace Engr) Join Date: Jul 2009 Location: Long Beach, CA Posts: 50 Rep Power: 10 Hi, It seems that the BCs are not defined correctly. Make sure you define Inlet BC including Front and Side walls of the domain. Also, for velocity inlet and pressure outlet regions, define velocity & pressure as 'Velocity of FirstOrderVofWave' and 'Hydrostatic Pressure of FirstOrderVofWave'. Furthermore, specify the Volume Fraction as 'Composite' and define them with corresponding Volume Fraction of Heavy OR Light Fluid of FirstOrderVofWave. I don't know your problem, but time-step of 0.003 s looks very small. Try 0.01s since your wave-length is 2.5s. Let me know if you have further questions.

December 11, 2010, 23:45
#3
New Member

Join Date: Apr 2009
Posts: 11
Rep Power: 10
I used pressure outlet on right hand side and velcoity inlet in left hand side and on top and bottom and sides of simulation domain. (kind of similar to DFBI tutorial in starccm manual).I also defines velocity and pressures correctly (as the tutorial)
I used T=0.01s and H=0.405m. Still it seems that waves deform abnormally as you see in these pictures. Can you please help me figure this out ? (looks at the figures I posted under this post)
Thank you so much
Attached Images
 Scene_3image00600.jpg (23.6 KB, 81 views) Scene_3image01200.jpg (23.6 KB, 64 views) Scene_3image01800.jpg (23.6 KB, 59 views) Scene_3image03000.jpg (23.5 KB, 57 views) Scene_3image03600.jpg (23.5 KB, 59 views)

 December 11, 2010, 23:59 #4 Member   Naimish Harpal (MS Aerospace Engr) Join Date: Jul 2009 Location: Long Beach, CA Posts: 50 Rep Power: 10 I see what's the problem. Most probably, you don't have mesh resolution on free surface (after breaking point). (infact this is the method used to avoid wave interaction near the side walls of domain by defining coarse mesh) Anyways, use fine mesh using control volume box method near entire free-surface. I am hoping that it will resolve the problem if your physics model setup is correct. Thanks.

December 12, 2010, 05:27
#5
New Member

Join Date: Apr 2009
Posts: 11
Rep Power: 10
I have refined the mesh on free surface (mesh size on free surface is about 2.4cm)
still the wave changes its shape although I am using inviscid model not sure why it becomes steeper as it progress.
Attached Images
 Scene_5image00100.jpg (22.1 KB, 36 views) Scene_5image01200.jpg (22.1 KB, 31 views) Scene_5image03600.jpg (22.1 KB, 33 views) Scene_5image05400.jpg (22.1 KB, 36 views) Scene_5image07100.jpg (22.3 KB, 40 views)

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post vof_grid FLUENT 0 July 6, 2007 08:47 mehdi icho Main CFD Forum 0 July 2, 2002 04:35 Mehdi BEN HAJ Main CFD Forum 2 February 12, 2002 12:07 Giovanni Main CFD Forum 16 September 24, 2001 08:25 Kim TaeMin Main CFD Forum 18 July 16, 2001 11:38

All times are GMT -4. The time now is 21:29.