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mAx July 24, 2002 10:53

oil vapour properties
Hi, I am simulating the oil flowfield within an hydraulic valve, and I have problems as I compare my results with the experience: the measured pressure drop was 30 bar at 40 C, and my converged solution shows a pressure drop about 40 bar!!! So I have 25% error, which isn t reasonnable. My BC's are following: velocity inlet & pressure outlet for a incompressible and turbulent problem! But, I have cavitation, because I have region with negative total pressure. So I suppose cavitation could affect the drop pressure. I am working with a mineral oil (rho 888 kg/m**3 & nu 46 mm**2/s). Now I have to set the cavitation model, BUT I ignore the oil vapour properties! Does anyone have the standard properties of such vapour (mineral oil), I mean density, viscosity & sturated vapour pressure? Regards mAx

gdv July 30, 2002 11:01

Re: oil vapour properties
I think that you can suppose indicative values such as:

density 10Kg/m^3 viscosity 10e-6 Kg/m-sec vaporization pressure 3000 Pa but it depends, obviously, on temperature.

I studied flow cases very similar to yours ( poppet valves and traditional directional valves) using water as fluid but I found some problems in the use of cavitation model, e.g., negative pressure values don't disappear and this don't change significantly pressure drop.


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