thermopyhsical Properties for buoyantBoussinesqPimpleFoam

Mike Jey · February 21, 2019, 05:18

Hi OpenFOAMers,

I am not so long in the matter of OpenFOAM. I am calculating an incompressible flow with buoyantBoussinesqPimpleFoam.

I was wondering because of following:

When I start the solver with the command buoyantBoussinesqPimpleFoam, the solver is reading the "thermophysicalProperties" although there is no such file in my constant-dictionary. I don't have such file in my case dictionary at all.

So which thermophysicalProperties does the solver get and from where?

A related question to this is, where do I find the definition of the density $\rho_0$ and the specific heat capacity

? I need $\rho_0$ to calculate the density field.

A look to the thermophysicalProperties of the compressible solver buoyantPimpleFoam shows me that there is a definition of

and so on...

Can I just copy that file to my buoyantBoussinesqPimpleFoam solver and is this for sure that these properties are used then?

Because the main thing is: the solver reads the thermophysicalProperties although there is no file in the case dictionary at all.

I am confused.

simrego · February 21, 2019, 08:06

Hi!

It reads the constant/transportProperties file.
This solver uses the Boussinesq approximation, so you have something like a "relative density" if it makes sense:
https://cpp.openfoam.org/v6/buoyantB...leFoam_8C.html
You have to calculate cp from the Prandtl number. (Actually Pr from cp)

Mike Jey · February 21, 2019, 09:52

Thank you very much. I have two more Topics which are a bit unclear for me:

First:
That means later in ParaView I can calculate my real density like this?:

$\rho = \rho_{ref} * (1 - \beta * (T - T_{ref}))$

$T_{ref}$ is defined in the transportProperties file but $rho_{ref}$ not. Do I understand right that a definition of $rho_{ref}$ in the pre-processing does not have any influence on the calculation? Thus, I just add my $\rho_{ref}$ in Post Process in ParaView?

Second:
How can I calculate

in ParaView? The Prandtl number requires $\nu_t$ , $\rho$ (with the equation above),

and heat conductivity $\lambda$ .

$Pr = \frac{\nu_t * \rho * c_p}{\lambda}$

So I am missing a value for $\lambda$ to get

calculated. Where it is defined? Or do I have to look up for a value at the reference temperature $T_{ref}$ in literature and add this also in Post Process (ParaView)?

February 21, 2019, 05:18	thermopyhsical Properties for buoyantBoussinesqPimpleFoam	#1
Mike Jey New Member Join Date: Aug 2017 Posts: 3 Rep Power: 8	Hi OpenFOAMers, I am not so long in the matter of OpenFOAM. I am calculating an incompressible flow with buoyantBoussinesqPimpleFoam. I was wondering because of following: When I start the solver with the command buoyantBoussinesqPimpleFoam, the solver is reading the "thermophysicalProperties" although there is no such file in my constant-dictionary. I don't have such file in my case dictionary at all. So which thermophysicalProperties does the solver get and from where? A related question to this is, where do I find the definition of the density $\rho_0$ and the specific heat capacity ? I need $\rho_0$ to calculate the density field. A look to the thermophysicalProperties of the compressible solver buoyantPimpleFoam shows me that there is a definition of and so on... Can I just copy that file to my buoyantBoussinesqPimpleFoam solver and is this for sure that these properties are used then? Because the main thing is: the solver reads the thermophysicalProperties although there is no file in the case dictionary at all. I am confused.

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February 21, 2019, 08:06		#2
simrego Senior Member anonymous Join Date: Jan 2016 Posts: 416 Rep Power: 14	Hi! It reads the constant/transportProperties file. This solver uses the Boussinesq approximation, so you have something like a "relative density" if it makes sense: https://cpp.openfoam.org/v6/buoyantB...leFoam_8C.html You have to calculate cp from the Prandtl number. (Actually Pr from cp)

February 21, 2019, 09:52		#3
Mike Jey New Member Join Date: Aug 2017 Posts: 3 Rep Power: 8	Thank you very much. I have two more Topics which are a bit unclear for me: First: That means later in ParaView I can calculate my real density like this?: $\rho = \rho_{ref} * (1 - \beta * (T - T_{ref}))$ $T_{ref}$ is defined in the transportProperties file but $rho_{ref}$ not. Do I understand right that a definition of $rho_{ref}$ in the pre-processing does not have any influence on the calculation? Thus, I just add my $\rho_{ref}$ in Post Process in ParaView? Second: How can I calculate in ParaView? The Prandtl number requires $\nu_t$ , $\rho$ (with the equation above), and heat conductivity $\lambda$ . $Pr = \frac{\nu_t * \rho * c_p}{\lambda}$ So I am missing a value for $\lambda$ to get calculated. Where it is defined? Or do I have to look up for a value at the reference temperature $T_{ref}$ in literature and add this also in Post Process (ParaView)?