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-   -   Density of fluid with respect to temperature and pressure (https://www.cfd-online.com/Forums/cfx/94049-density-fluid-respect-temperature-pressure.html)

 akash_max November 3, 2011 15:16

Density of fluid with respect to temperature and pressure

Hi All,

I not able to find how to input material property for the fluid(diesel) with respect to temperature and pressure. I have complete data that is pressure range 0 to 2000 bar and temperature range 0 to 200 degree Celcius.

Do i need to write a expression to it or any way i can just feed the excel data into the CFX where in it produces the graph and uses the same.

Similarly I need to give cavitation saturation pressure with respect to temperature.

If this is done then i can run my model with thermal conditions first and then the cavitation model to find the effect of thermal effects on cavitation.

I need to check out with raise in temperature how much the cavitation raises as the fluid passes through different orifice.

I need to also give specific heat capacity with respect to temperature and also the dynamic viscosity with respect to temperature.

I am using thermal energy with inlet as total pressure and temperature and outlet as static pressure. Wall being the adabatic.

Kindly help me out resolving this issue.

Best Regards
Akash A V

 stumpy November 3, 2011 16:46

What you want is bi-linear interpolation since the density depends on two variables. There's no built-in bi-linear interpolation in CFX-Pre, so yes, you need to come up with an expression that describes the density as a function of (T,p). I don't think Excel can curve fit a bi-linear function, but it would be nice if it could (and please tell me how to do it!). Anybody know of any software that can do that curve fit?

 akash_max November 4, 2011 09:12

Hi,

I would request to kindly send me formulae for density variation with respect to temperature and pressure separately. (Density with repect to temp)( Density with repect to temp)

So that I will assign them individually and check how much is the variation.

Please let me know the CEL function for above mentioned variations.

Regard
Akash A V

 ghorrocks November 6, 2011 05:54

You already have defined the density as a function of pressure. Just do the same for temperature and it is straightforward from there.

 mauricio November 6, 2011 10:00

Try a software like Curveexpert to find a fit for your temperature and pressure data points. The just use that expression in the material properties. Do check how precise is the fit though.

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