|September 8, 2012, 07:27||
Negative absolute pressure
Join Date: Apr 2009
Posts: 12Rep Power: 6
I've a question regarding negative absolute pressure values I get in the flow field and their meaning.
I ran an incompressible transient laminar flow past a circular cylinder with zero reference pressure. When I check the variation of absolute pressure in certain points close to the cylinder, I get negative values. I should add the problem is not physically well defined in means of density, visocisty etc., but rather theoretic.
Although negative values of abolute pressure are not physical as far as I know, can I trust those values?
|September 8, 2012, 08:17||
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 8,254Rep Power: 67
Negative absolute pressure usually means that the liquid will cavitate and this will eliminate the negative pressure.
However negative absolute pressure is physically possible - cavitation takes time to happen. Not much time, but for that short period of time a fluid sustains a negative absolute pressure. This is an effect of subcool/superheats and other non-equilibrium phase change.
But for your analysis, it is up to you. If you are doing a theoretical analysis you probably don't care about cavitation. But if you are designing a real system you might and in that case you better see if that cavitation is going to be a problem. Alternately you might have a rare case where you really do have negative absolute pressures.
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