[sreehahaha]

Dear Foamers,

I'm trying to model water using the rhoCentralFoam solver and I found the thermoPhysicalProperties file for water from Toby's website: https://holzmann-cfd.com/community/b...operties-water

that has the following snippet:

thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       polynomial;
    thermo          hPolynomial;
    equationOfState icoPolynomial;
    specie          specie;
    energy          sensibleEnthalpy;
}

However, when I try to run the solver, I get an error saying

Unknown type type heRhoThermo
Supported type types:
1
(
hePsiThermo
)

Can someone please help me to figure out why I'm getting this error? I'm using OF9.

Many thanks in advance.
S

[dlahaye]

The error indicates that rhoCentralFoam only supports hePsiThermo.

Change thermodynamics to hePsiThermo (more versatile at possibly higher computational cost)

Or change solver to rhoPimpleFoam (and thus algorithms to solve the case)

Or extend rhoCentralFoam to heRhoThermo (possibly of limited use)

[sreehahaha]

Originally Posted by dlahaye

The error indicates that rhoCentralFoam only supports hePsiThermo.

Change thermodynamics to hePsiThermo (more versatile at possibly higher computational cost)

Or change solver to rhoPimpleFoam (and thus algorithms to solve the case)

Or extend rhoCentralFoam to heRhoThermo (possibly of limited use)

Thank you, dlahaye, for the quick reply. When I use hePsiThermo, I get another error saying I cannot use 'icoPolynomial'. Could you please suggest a workaround to avoid this impasse so that I can use Tobi's polynomials to evaluate density etc.?

Many thanks,
S

[dlahaye]

What is yr constant/thermophysicalProperties?

What are Tobi's polynomials? Can you use standard Janna instead?

Domenico.

[sreehahaha]

Originally Posted by dlahaye

What is yr constant/thermophysicalProperties?

What are Tobi's polynomials? Can you use standard Janna instead?

Domenico.

In the link above, Tobi has given the thermophysicalProperties file. I just copied it for water. I guess it can only be used with solvers that support heRhoThermo. I haven't tried using Janaf though. Will give it a try, thanks.

S

[dlahaye]

rhoCentralFoam for water flow? Really? What are you trying to simulate?

[sreehahaha]

Originally Posted by dlahaye

rhoCentralFoam for water flow? Really? What are you trying to simulate?

It's a fluctuating hydrodynamics simulation of water. All the fields fluctuate about a mean value, and so I'll need a compressible solver.

I thought rhoCentralFoam might be the best one as it is density based, and so I can plug in an appropriate EOS for water. Tobi's EOS was a starting point. Do you think I'd be better off trying another solver? It'd be very helpful if you have any suggestions.

Thanks,
S

[dlahaye]

I am surprise flow of water to be compressible. What is the Mach number of the flow?

[sreehahaha]

Originally Posted by dlahaye

I am surprise flow of water to be compressible. What is the Mach number of the flow?

As an example, if you're familiar with molecular dynamics simulations, local density fluctuations arise due to the thermal motion of atoms/molecules. This local rarefaction gets rectified in the next instant due to atoms moving into it, simultaneously creating rarefaction at a different location. As you may know, this happens even in liquids and solids and not just in gas, as thermal motion of molecules is ubiquitous. This density fluctuation causes all other fields (pressure, velocity etc.) to fluctuate as well.

Fluctuating hydrodynamics simulations are the continuum counterpart of molecular dynamics simulations. So, here also, all fields fluctuate around their mean values. This is achieved by adding divergence of some stochastic fluxes to NS and energy equations that satisfy the fluctuation-dissipation theorem. As a result, if you look at water simulated by FH, you'll see local fluctuations in all fields even though the global values of the same fields remain constant. So, the Mach number is irrelevant here to address compressibility.

S