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-   -   Thermophysicalproperties in rhoCentralFoam (http://www.cfd-online.com/Forums/openfoam-solving/58722-thermophysicalproperties-rhocentralfoam.html)

 srinath July 18, 2008 02:24

Hello I am looking at the

Hello

I am looking at the file in wedge15Ma5/constant/thermophysicalProperties
It has the following lines

thermoType hThermo<puremixture<consttransport<speciethermo<hc onstthermo<perfectgas>>>>>;

mixture normalisedGas 1 11640.3 2.5 0.0 0.0 1.0;

What does this mean?
Previously for example in sonicFoam, i had to just set R,Cv,mu etc
Looking at the code, it appears that we can specify Prandtl no.
How do we do that?
Looking at the first entry in thermoPhysicalproperties, it appears we can change eqn of state. But an ideal gas eqn of state seems to be hardcoded in. Am i correct in saying this?

Thanks
Srinath

 Alan April 18, 2010 03:34

This is setting the thermo physical properties of your simulation.

The first line determines which models will be used in the simulation. Look here:

http://www.openfoam.com/docs/user/thermophysical.php

for more details. The second line is defining the parameters for the thermophysical models.

The first number is the number of moles, the second is the molecular mass (this value is normalised so as to give a velocity of V=1m/s=Ma 1). The third number is the specific heat capcity at constant pressure. The fourth is the heat of fusion. Fifth is the viscosity and the sixth is the Prandtl number.

 fluidzhang November 24, 2010 10:08

Quote:
 Originally Posted by Alan (Post 255101) This is setting the thermo physical properties of your simulation. The first line determines which models will be used in the simulation. Look here: http://www.openfoam.com/docs/user/thermophysical.php for more details. The second line is defining the parameters for the thermophysical models. The first number is the number of moles, the second is the molecular mass (this value is normalised so as to give a velocity of V=1m/s=Ma 1). The third number is the specific heat capcity at constant pressure. The fourth is the heat of fusion. Fifth is the viscosity and the sixth is the Prandtl number.
Hello, Alan.
the second is the molecular mass (this value is normalised so as to give a velocity of V=1m/s=Ma 1). I agree with you as to the second term,now I'd like to ask the unit of the molecular mass ,and how to normalise this term,and why the velocity can be 1 m/s,or Ma?How to understand them? Please help me,expect you!Thank you.

 azaharov May 11, 2011 09:58

What means two last parameters in
mixture normalisedGas 1 11640.3 2.5 0.0 0.0 1.0;

In http://www.openfoam.com/docs/user/thermophysical.php I read what these are dynamic viscosity mu and Prandtl number, i.e. mu = 0, inviscid gas (but in in sonicFoam boundary condition for velocity is No Slip Wall, i.e. for viscosity gas, is not it?) and Pr = Cp *mu /k (if mu = 0 then Pr = 0 is not it ?). Please help me to understand values of these parameters. Thank you.

 m2montazari June 20, 2011 14:55

hi azarahov,
I had the same question as you asked; but when setting the Pr=0 running the case returns error!
so I thought and I fund out the problem... when we have inviscid flow, as miu=0, k would be zero too, so Pr=0/0 . but I dont know what value should I put for Pr instead of 0/0. maybe any value other than zero returns same result(it should be tested) because for inviscid flows Pr number should be vanished.
if you found any better and more complete answer, I would be happy if you tell.
thanks,

 Rophys September 30, 2011 06:58

Hello all,

I'm new in the OpenFoam and I'm using the rhoCentralFoam to study a convergent-divergent nozzle as a initial case. I have some questions about the thermophysical properties and I hope somebody help me with this.

1) rhoCentralFoam is a inviscid solver ? In the Openfoam web site only have the information that it is density based. If the answer is yes, I have the same problem with the Prandtl number.

2)Where I can find the heat of fusion for a determined species ? I use to go to the NIST website to get some information but it don't have information about heat of fusion only enthalpy.

3)Somebody could explain me which units is used to cp, mu, Hf, nmols, molecular mass, etc ? I try to compare the values in a tutorial case with some tabulated values but I din't find anything similar used in this case. There is some specific table to set up the thermophysical properties for the Compressible Solvers ?

Thanks

 m2montazari September 30, 2011 10:54

hi,
as I know, rhocentralfoam is laminar solver.
all properties of fluid is set in "thermophysical properties" file in constant folder. you can look at the openfoam help pdf to see more information. dont look at tables to find a similar gas. usually openfoam tutorial cases use air or normalized gas. a normalized gas is a virtual gas which has 1 m/s speed of sound in 1 K temperature and 1 Pa pressure. with ideal gas relation you can find molecular weight and ... which is needed in thermophysical properties.
though openfoam 1.7 and 2.0 is a bit different about the structure of this file.
yours,

 Rophys September 30, 2011 11:07

Thanks for this, your help was very useful.

I have another question. I don't want to use a normalized gas, so, how I can set up a case using a specific gas like nitrogen or argon ?

I' m also using the sutherlandTranspor and janafThermo. Where I can find about it ? There is some table or book where I can this informations ?

Thanks

 m2montazari September 30, 2011 15:47

hi rodrigo,
you can use any gas simply by typing its molecular weight, cp, miu, Pr, ... according to what is said in the userguid U-178. it has an example of janaf and sutherland for fuel. you can replace numbers with nitrogen or ... properties. the janaf tables are in here:http://www.sciencedirect.com/science...21961472900365
also you can take a look at http://openfoamwiki.net/index.php/Janaf . it may help!
yours,

 Rophys September 30, 2011 19:07

I opened the file that exist in the website that you recommended me and I find the following data do N2 (just a example).

N2 TPIS 1978 v1 pt2 p207.
3 tpis78 N 2.00 0.00 0.00 0.00 0.00 0 28.0134800 0.000
200.000 1000.0007 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 0.0 8670.104
2.210371497D+04-3.818461820D+02 6.082738360D+00-8.530914410D-03 1.384646189D-05
-9.625793620D-09 2.519705809D-12 7.108460860D+02-1.076003316D+01
1000.000 6000.0007 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 0.0 8670.104
5.877124060D+05-2.239249073D+03 6.066949220D+00-6.139685500D-04 1.491806679D-07
-1.923105485D-11 1.061954386D-15 1.283210415D+04-1.586639599D+01
6000.000 20000.0007 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 0.0 8670.104
8.310139160D+08-6.420733540D+05 2.020264635D+02-3.065092046D-02 2.486903333D-06
-9.705954110D-11 1.437538881D-15 4.938707040D+06-1.672099736D+03

According to the User Guide (U-177) Cp is calculated as follow:
Cp=R((((a1T+a3)T+a2)T+a1)T+a0)
and we need 2 constants of integration a5 and a6.
My question is, which of this parameters corresponds to a0, a1, a2, a3, a4, a5 and a6 ?

 sani September 29, 2012 08:41

i start work whit rhoCentralFoam for simulating airfoil.
i have some problem,can you help me please?

 Linse October 1, 2012 08:32

Quote:
 Originally Posted by sani (Post 384185) my name is ahmad i start work whit rhoCentralFoam for simulating airfoil. i have some problem,can you help me please?

i.e. don't hijack a thread but open up a new one with a descriptive name. And then ask questions that can be answered.

Then you can be quite sure that somebody at least will think about the problem you have. And most probably then you will get an answer as well!

Cheers,
Bernhard

 sani October 2, 2012 10:04