Custom Fluids (Hydraulic Oil)
 

Hi CFD fans/experts,

Firstly I really appreciate any help at all as I've been through many ANSYS CFD customer portal tutorials, forum posts etc. but am still struggling to find a solution :(

I am attempting to model cavitation of hydraulic fluids through a pipe orifice restriction. I am trying to simulate water-glycol (40% water content) in the CFD-pre material designer. I only know its viscosity, density, operating temperature (and %diol polymers in fluid, not sure if relevant?).

I am wondering if to model the fluid as a fixed composite mixture or pure substance.

If doing it as a pure substance do I do a multiphase with water vapour (in the assumption that it has a higher vapour pressure and hence will cavitate out before the glycol itself).

In doing it as a fixed composite, do I set the child materials as water and glycol (don't know what type though)? however I only know the combined viscosity and density; and what is the mass fraction in this case?
Are mixture properties okay to not utilise if unknown? or should I attempt (as fluid properties obtained from an experimental report) to find them online?


Thanks in advance, any assistance would be much appreciated!
Regards,
Sam

The CFX tutorials has an example on how to set up cavitation models.

I would start this model using the simple bulk material properties, as per the example. I would more complex than that if you have a clear reason to do so - do you have a good reason why bulk properties would not be adequate?

Thank for the quick response!

Assuming by bulk material properties you mean a pure substance model (for the water-glycol), and create multiphase fluid with this liquid and vapor (as seen in hydrofoil cavitation tutorial?) ?

In doing this do I just use the water vapor provided, even though I'm using a water-glycol fluid?

Thanks again mate!

Sam

Yes, by bulk properties I mean simply a fluid with a density, viscosity and vapour pressure representative of the true water-glycol mixture.