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-   -   about L-J Characteristic Length (http://www.cfd-online.com/Forums/fluent/33266-about-l-j-characteristic-length.html)

KEVIN March 18, 2004 07:39

about L-J Characteristic Length
 
Who can tell me what is the L-J Characteristic Length and L-J Energy Parameter in the fluent software? How can I get the details about them, thank you very much!!!!!

George March 18, 2004 15:42

Re: about L-J Characteristic Length
 
I accidentaly worked some time ago on Molecular Dynamics problems, so I should be able to answer this one..:)

Well, L-J stands for Lennard-Johnson potential, which describes the mutual forces that exist among atoms in a molecule. You can look in any textbook on solid state physics or kinetic theory of gases. (E.g. a classical reference from the first area: KITTEL, C.: Introduction to Solid State Physics, 5-th edition, John Willey & Sons Ltd., 1976)

KEVIN March 19, 2004 02:23

Re: about L-J Characteristic Length
 
Thank you very much, George. I get the book which you mentioned in the message. It just tells me what is the L-J potential, but how can i get the L-J Characteristic Length and L-J energy parameter. Do you know where i can get these parameters, or i have to calculate them according some formulations, and what's form of these formulations? Thank you,very very much!

cg March 22, 2004 20:53

Re: about L-J Characteristic Length
 
Kevin, Look at the transport database from Chemkin. The L-J parameters for many species are listed in there.

KEVIN March 22, 2004 21:00

Re: about L-J Characteristic Length
 
cg,thank you very much! Can you tell me whether the chemkin is a software or a book? thanks a lot!

KEVIN March 23, 2004 09:07

Re: about L-J Characteristic Length
 
thank you very much! i have got the answer from the chemkin. i have another question, what's the degrees of the freedom, where can i get the details about it? thank you very much@

George March 23, 2004 17:53

Re: about L-J Characteristic Length
 
Hi Kevin, I wonder why are you taking such trouble investigating L-J potentials? Firstly, because the parameters (except perhaps for the number of degrees of freedom) are by no means possible to derive by you alone. And secondly, you need them only in order to be able to use kinetic theory of gases option for calculation of some physical properties. However, experimental data are substantially more accurate, namely if the database offers polynomial or piecewise polynomial approximation.

Regards George

KEVIN March 24, 2004 22:53

Re: about L-J Characteristic Length
 
Hello! Everyone , now i simulate a chemical reaction between gas(nh3) and porous solid(cacl2),but i met a problem in defining the material property. In the fluent, the unit of the standard state enthalpy and standard state entropy is j/kgmol and j/kgmol.k,respectively. But i search the unit of the stand state enthalpy and standard state entropy is j/mol and j/mol.k respectively. Who can tell me how to switch between these two units? Thank you very much!

kevin March 25, 2004 09:33

Re: about L-J Characteristic Length
 
Hello! Everyone ,I met the problem about the Arrhenius Rate --1.How to get the Pre-Exponential Factor --2.How to calculate the Activation Energy --3.How to calculate Temperature Exponent

PS:I simulate the chemical reaction between the gas(nh3) and solid(cacl2)

Thank you very much!!!!


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