Compressible Water-Sloshing

rajeshfromindia · February 21, 2013, 17:33

Hello Everyone,
I am investigating the effects of compressibility on sloshing. The fluids in action or air and water. While having both fluids as compressible, i.e. air as ideal gas and water with density as a function of pressure, I am able to get results (attached) as expected. But when I make the water alone to be compressible I get very high pressure values (attached results). The behaviour of water looks the same in both cases when I see the water volume fraction contours. The Reference Pressure I am using for both the cases is 1 atm and the relative pressure is 0 pa. Since I am using a six sided no slip wall geometry, I have specified a pressure level of 1Pa on the top wall. Could some one please help me out with what actually the error must be. I have also attached my CCl file.
Thanks,
Rajesh.

ghorrocks · February 22, 2013, 05:57

Your CCL is only the first bit. All the interesting bits are not included.

Why not use a reference pressure of 1atm+1Pa, then use a top boundary pressure of 0Pa? That is how the reference pressure is meant to work.

Are you using surface tension?

There are lots of free surface sub models. I recommend you have a look at the available options and see what they do. Some may work better for you.

rajeshfromindia · February 22, 2013, 17:57

Hello Mr. Ghorrocks,
Thanks a lot for your swift reply. I am not using surface tension and I will run it as you have said and see how my results vary.
Thank You,
Rajesh.

ghorrocks · February 23, 2013, 05:50

Surface tension makes this type of modelling much more complex - so things are considerably simplified by not including it.

There are many free surface smoothing algorithms, smoothing levels and differencing schemes. I recommend you try them to see if any work better than the defaults.

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February 22, 2013, 05:57		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Your CCL is only the first bit. All the interesting bits are not included. Why not use a reference pressure of 1atm+1Pa, then use a top boundary pressure of 0Pa? That is how the reference pressure is meant to work. Are you using surface tension? There are lots of free surface sub models. I recommend you have a look at the available options and see what they do. Some may work better for you.

February 22, 2013, 17:57		#3
rajeshfromindia New Member Rajesh Join Date: Nov 2012 Posts: 8 Rep Power: 14	Hello Mr. Ghorrocks, Thanks a lot for your swift reply. I am not using surface tension and I will run it as you have said and see how my results vary. Thank You, Rajesh.

February 23, 2013, 05:50		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Surface tension makes this type of modelling much more complex - so things are considerably simplified by not including it. There are many free surface smoothing algorithms, smoothing levels and differencing schemes. I recommend you try them to see if any work better than the defaults.