# Contrib/Janaf

(Redirected from Janaf)

# 1 old janaf model

OpenFOAM uses the old janaf tables from which the temperature dependent values of Cp, H and S are valuated. Therefor the old janaf format uses 7 coefficients and 2 polynomials for a lower and a higher temperature range. The old janaf tables are valid for temperatures up to 6000 K.

Cp(T) = R( a + aT + aT^2 + aT^3 + aT^4 )
H(T) = R( aT + (aT^2)/2 + (aT^3)/3 + (aT^4)/4 + (aT^5)/5 + a )
S(T) = R( a lnT + aT + (aT^2)/2 + (aT^3)/3 + (aT^4)/4 + a )

ftp://ftp.technion.ac.il/pub/supported/aetdd/thermodynamics/THERM.DAT

The old janaf model is implemented in the application "dieselFoam" and can be tested in the test case "aachenBomb".

In OpenFOAM the same reader, which reads the thermodynamic data of the janaf table also contains the input data of the laminar viscosity. Therefor the Sutherland formula is used, which shows a linear increasing of the viscosity depending on the temperature. The input data is hard coded and describes the temperature dependent viscosity of pure nitrogen. In a case with nitrogen as environmental gas this could be an acceptable approximation, if there are no ionization processes.

# 2 new janaf model

For some application the temperature range up to 6000 K is not sufficient. In an application containing plasma (e.g. arc welding) the temperature range could be up to 30000 K. Therefore the newer janaf model is needed which handles a larger temperature range up to 30000 K. The temperature dependent values of Cp, H and S are calculated with 3 polynomials using 9 coefficients.

Cp(T) = R( a/T^2 + a/T+ a + aT + aT^2 + aT^3 + aT^4 )
H(T) = R( -a/T + alnT + aT + (aT^2)/2 + (aT^3)/3 + (aT^4)/4 + (aT^5)/5 + b )
S(T) = R( -a/(2*T^2) - a/T + a lnT + aT + (aT^2)/2 + (aT^3)/3 + (aT^4)/4 + b )

http://www.galcit.caltech.edu/EDL/public/thermo/thermo.inp

For temperatures above 10000 K the Sutherland formula is not a good approximation anymore. The beginning ionization leads to an decreasing of the laminar viscostiy. Therefor a transport model based on polynomials should be used instead.

## 2.1 Implementation to OpenFOAM 1.5.x

Iyer Arvind Sundaram has implemented the new janaf model to OpenFOAM 1.5.x. You can download his patch here:

## 2.2 Implementation to OpenFOAM 1.7.x

I have updated Iyers new janaf model to OpenFOAM 1.7.x. In addition I have also updated the transport model. It now handles laminar viscosities of different species for temperatures up to 30000 K. The polynomials of the viscosities are still hard coded in the chemkin reader and contains only species which are interesting for arc welding applications. The polynomials are calculated with the transport model of our research group.

• http://elib.dlr.de/65881/1/hoffmann2008cs.pdf
• Content of the document:
Thomas Hoffmann, Georgiana Baldea, Uwe Riedel, Thermodynamics and transport properties of metal/inert-gas mixtures used for arc welding, Proc. Combust. Inst. 32 (2), 3207-3214, 2009.

An update to the new janaf model will overwrite the old janaf model and the old sutherland transport model. Sorry, I know, that this is not a good OpenFOAM style, but I do not have much time. - Bfisch90

### 2.2.1 How to install

2.Replace the old folders with the updated folders, which you can find here:
~/OpenFOAM/OpenFOAM-1.7.x/src/thermophysicalModels/specie/transport/sutherland
~/OpenFOAM/OpenFOAM-1.7.x/src/thermophysicalModels/specie/thermo/janaf