Hi Clement,
Have you managed to figure this out? I am also looking to implement an equation of state and am not sure what to make of the psi term. Referring to the documentation for totalPressure boundary condition (which is more in line with my own interests), psi is defined as compressibility and has units m^2/s^2. Beyond that though, I have not seen any documentation about what it actually is ... Edit: Continuing with the dimensional line of thought, so the units work out in that regard. Regards, Aaron |
Hi
I think the compressibility is actually the reverse that is being defined above. It is psi = rho/p which makes it a isothermal compressibility Thanks RR |
totalPressure definition
Hi,
In totalPressureFvPatchScalarField.H we can read that for compressible supersonic flow the total pressure is defined as : \f[ p_p = \frac{p_0}{(1 + 0.5 \psi G |U|^2)^{\frac{1}{G}}} \f] where \vartable p_p | pressure at patch [Pa] p_0 | total pressure [Pa] \gamma | ratio of specific heats (Cp/Cv) \psi | compressibility [m2/s2] G | coefficient given by \f$\frac{\gamma}{1-\gamma}\f$ \endvartable What compressibility is ? is its dimension really m2/s2 ? and really not s2/m2 ??. I would expect s2/m2 in order to obtain psi*U^2 as an unidimensional number .. I am also surprised by the G definition. It is really \frac{\gamma}{1-\gamma} ? I would expect the inverse frac{1-\gamma}{\gamma} ? Does someone has an opinion on it? Regards Fanny |
Hi
I see it is s2/m2 because in the above equation it is multiplied by U2 to get a scalar value. Best Regards, RRK |
from the Programmer's Guide v 3.0.1
|
Quote:
It can be in isothermal case, and in adiabatic case. Can we be sure that psi is determined by the first formula in all cases? |
Quote:
Please correct me if I am wrong! ES7 |
OpenFOAM docs
This might be useful. You can look up different versions (v3 and above).
https://cfd.direct/openfoam/user-gui...hermophysical/ |
Add a non-linear equation of state to foam
Hi foamers,
I want to add a non-linear equation of state (JWL) to foam to use in sonicFoam. In this equation, I need to calculate rho, Cp, h, s, psi, Z, and cpMcv and some functions such as: correct (which is used in EEqn.H: thermo.correct() ) pThermo(which is used in createFields.H: thermo.pThermo() ) p (which is used in createFields.H: thermo.p() ) rho (which is used in createFields.H: thermo.rho() ) he (which is used in createFieldRefs.H: thermo.he() ) psi (which is used in createFieldRefs.H: thermo.psi() ) But JWL is non-linear and calculation of parameters are not as easy as perfectGas! However, I have calculated rho using Newton method in rho() function. But I don't know how to calculate the others! Thanks |
Dear foamers,
my last problem is not solved yet! In addition I want to know: 1- How can I calculate "h", "Cp" for my new equation of state? why Cp and h are zero for perfectGas model in openFoam? and how did they calculate "s=-R*log(p/Pstd)" ? Thanks |
JWL implementation that works with OpenFOAM
Hi,
Yes, we have just released a new solver (blastFoam) which includes the JWL equation of state (an extensions to model afterburn), as well as several other useful and interoperable equations of state (e.g. ideal gas, stiffened gas, tait, cochran-chan, van der waals, JWL), flux schemes (HLLC, AUSM+, Kurganov/Tadmor), and multiple examples/tutorial cases. Source, user guide and examples are available here: https://github.com/synthetik-technologies/blastfoam Hope this helps! Peter Vonk Synthetik Applied Technologies |
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