[m0h]

Hello Community,

I have one more question. I am trying to simulate the properties of oil.
My model should use buoyancy effects. The dynamic viskosity, and the density are temperature dependent. My question is the density:

I did this for an oil with the following expression:

myroh = 883[kg m^-3]/(1+(T-288.15[K])*0.0007 [K^-1])

The density changes with the thermal expansion factor of 0.0007.

Question: Is it neccessary to enter the thermal expansivity factor in CFX at the material properties (Buoyancy Properties), because I already considered it at the density.

If the density would change automatically with the temperature, from my point of view it would be neccessary to have an field density and to give the information at which temperature the fluid has this certain density.

Thank you in advance,
m0h

[Opaque]

It would be a good exercise to read the ANSYS CFX Solver Theory Guide section about Buoyancy. From the description of the Full Buoyancy and Boussinesq models, you will see when is the thermal expansion coefficient needed, and when it is not.

The values needed can be summarized as

1. Full Buoyancy: Reference Density
2. Boussinesq: Reference Temperature and Thermal Expansivity for the material selected

Hope the above helps,

[JuPa]

If you use your own density function, the Boussinesq option is not available and the density difference option is. If you use density difference, it doesn't use the thermal expansion factor in the material properties.

[hichemsoft CFX]

you mean that you want to simulate a mixed convection, if this you want, you to check -g (acceleration of earth), and you inject to modele

good luck

[m0h]

Hello all, thank you very much for the hints. i tried to find bousinessq, but as you said its only available if no temperature function is entered. thank you very much!

m0h