rhoPimpleFoam Initial Density

kamakura · December 22, 2020, 08:03

Dear Foamers,

I am trying to calculate a compressible fluid using rhoPimpleFoam(OpenFOAM1806).
My question is the calculation of density.
I use the ideal gas law (perfect Gas) to calculate density.
Do you know how the density at the start of the calculation is calculated?
It was found that the density was calculated from the pressure, gas constant, and temperature, and the initial value of the pressure was read in createfields.H.
I didn't know how the initial temperature values were read.

Thanks in advance.

mAlletto · December 22, 2020, 16:36

https://cfd.direct/openfoam/user-gui...hermophysical/

See equation of state

kamakura · December 23, 2020, 00:46

Dear mAlletto,

Thank you for your reply. I apply perfectGas to calculate the density.

I understand that the density field is calculated using pressure field, temperature field, and gas constant at any time step (after starting time loop).
I can not understand that how the density is calculated BEFORE starting time loop.
In the createfields.H, pressure is initialized, then, density is initialized.
But where Temperature is initialized?

I apologize for the difficulty in reading in my poor English.

mAlletto · December 23, 2020, 03:22

The temperature is calculated in the thermopackage from the energy.
https://caefn.com/openfoam/temperature-calculation

kamakura · December 23, 2020, 03:44

Dear mAlletto,

Thank you for your reply.

Thanks to the link you pasted, I understand the existence of a function that transforms energy into temperature.

At first of the calculation, temperature is initialized using the function.

Thank you for your kindness.

December 22, 2020, 08:03	rhoPimpleFoam Initial Density	#1
kamakura New Member Join Date: Jul 2020 Posts: 5 Rep Power: 6	Dear Foamers, I am trying to calculate a compressible fluid using rhoPimpleFoam(OpenFOAM1806). My question is the calculation of density. I use the ideal gas law (perfect Gas) to calculate density. Do you know how the density at the start of the calculation is calculated? It was found that the density was calculated from the pressure, gas constant, and temperature, and the initial value of the pressure was read in createfields.H. I didn't know how the initial temperature values were read. Thanks in advance.

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December 22, 2020, 16:36		#2
mAlletto Senior Member Michael Alletto Join Date: Jun 2018 Location: Bremen Posts: 616 Rep Power: 16	https://cfd.direct/openfoam/user-gui...hermophysical/ See equation of state

December 23, 2020, 00:46		#3
kamakura New Member Join Date: Jul 2020 Posts: 5 Rep Power: 6	Dear mAlletto, Thank you for your reply. I apply perfectGas to calculate the density. I understand that the density field is calculated using pressure field, temperature field, and gas constant at any time step (after starting time loop). I can not understand that how the density is calculated BEFORE starting time loop. In the createfields.H, pressure is initialized, then, density is initialized. But where Temperature is initialized? I apologize for the difficulty in reading in my poor English.

December 23, 2020, 03:22		#4
mAlletto Senior Member Michael Alletto Join Date: Jun 2018 Location: Bremen Posts: 616 Rep Power: 16	The temperature is calculated in the thermopackage from the energy. https://caefn.com/openfoam/temperature-calculation

December 23, 2020, 03:44		#5
kamakura New Member Join Date: Jul 2020 Posts: 5 Rep Power: 6	Dear mAlletto, Thank you for your reply. Thanks to the link you pasted, I understand the existence of a function that transforms energy into temperature. At first of the calculation, temperature is initialized using the function. Thank you for your kindness.