CFD Online Logo CFD Online URL
Home > Forums > STAR-CCM+

VOF damping at inlet

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

LinkBack Thread Tools Display Modes
Old   March 4, 2014, 10:04
Default VOF damping at inlet
Arun Krishnan.L.H
Join Date: Jan 2013
Posts: 75
Rep Power: 7
arun7328 is on a distinguished road
Dear Sir,

I am simulating a case of barge in regular waves and finding the heave and pitch response of the barge. I am comparing this with experimental values. My barge dimensions are ,
L: 2.445 m B: 0.6 m and D : 0.25 m T: 0.12 mt

Set up: The shape of the barge is rectangular with a chine like shape at the fwd. The length of the wave is 6.8 m and its amplitude is 0.025 m( wave period 2.08 secs). I have used first order wave.

Domain: The inlet is 1.5 wavelengths from the barge. Outlet is 2 wavelengths + 2 wavelengths damping zone. Symmetry plane is used to model only half of the domain. The width of the domain is 6m (same as the towing tank). I have used DFBI+morphing to simulate this condition.

Problem: It seems to be working fine for sometime and then the heave starts to fluctuate. I have shown a plot of heave and pitch. The pitch remains steady. When I take the amplitude of heave at the steady condition(3-8 secs) and calculate the RAO, it is very close to the experimental value. I suspected wave reflections so tried to extend the outlet to 8 wavelengths including 2 wavelengths damping zone, and still found the same problem. I have now put another model for running with 4 wavelengths at the inlet. I suspect the problem is because of reflections from inlet. I have also attached the wave elevation plot at 1 wavelength from the barge towards the inlet. It can be seen that there is a spike at about 13-14 secs and also a slight phase shift ( due to the wave radiated from barge?).

I wanted to know if it is possible to give a damping at the inlet to absorb the wave radiated from the barge due to its symmetric motions? I tried to apply a damping field function but found it damps the inlet waves as well. In STAR the damping is not direction dependent right? Can you please suggest a method and help me with this? Please be kind to give some suggestions. I have been working on this for more than a month now.

Ps: I am using an inviscid model. When i tried to simulate the same using a cylinder in waves, I get a good response.
arun7328 is offline   Reply With Quote

Old   March 4, 2014, 10:07
Arun Krishnan.L.H
Join Date: Jan 2013
Posts: 75
Rep Power: 7
arun7328 is on a distinguished road
sorry i forgot the attachments
Attached Images
File Type: jpg elevation.jpg (40.2 KB, 30 views)
File Type: jpg heave.jpg (36.6 KB, 22 views)
File Type: jpg pitch.jpg (31.9 KB, 18 views)
arun7328 is offline   Reply With Quote


Thread Tools
Display Modes

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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
VOF Inlet condition Rizwan FLUENT 14 April 30, 2017 07:35
VOF Damping lava12005 STAR-CCM+ 5 December 1, 2014 21:16
How to set up the inlet boundary condition for a low pressure case? beastieboys6 FLUENT 3 April 10, 2012 22:46
plz rply urgent regrding vof model for my system garima chaudhary FLUENT 1 July 20, 2007 08:37
urgent query regarding vof model plz rply Garima Chaudhary FLUENT 0 July 13, 2007 02:20

All times are GMT -4. The time now is 05:06.