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Problem with negative pressure
Posted 22 feb 2012, 11:26 GMT-5 Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.2 1 Reply
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I'm using a 2D Laminar Two-Phase flow to simulate a droplet of water of radius=0.25m in engine oil (which is a square of 1.28 by 1.28 m)
The Young-Laplace equation states that the pressure difference across the interface will be equal to the surface tension divided by the radius of the droplet.
To test this relationship I am simply inputting a user defined surface tension and recording the pressure it gives me, however for a few surface tension values I use it gives a negative pressure, the difference of the two negative pressures still proves the relationship but why is it only negative for certain surface tension values?
It would also help if someone could tell me how to access the surface tension values from the library, I could use a water/olive oil surface tension coefficient but I cant find the value anywhere.
Hello Sam Bull
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Regarding the negative “gauge” pressures, the Young-Laplace equation only controls the pressure difference along the interface. The actual values on both sides of the interface depend on the rest of the model.
Nagi Elabbasi
Veryst Engineering