CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   NUMECA (http://www.cfd-online.com/Forums/numeca/)
-   -   Kinetic Theory (http://www.cfd-online.com/Forums/numeca/50901-kinetic-theory.html)

Tommaso June 24, 2003 12:04

Kinetic Theory
 
hi

In the ideal gas model using the kinetic theory for Cp and K, which are the values to insert in degrees of freedom...........

thanks in advance payment

BAK_FLOW July 25, 2003 15:53

Re: Kinetic Theory
 
Hi,

the number of translational and rotational modes are added up. For monatomic gasses this is 3 for diatomic this is 5 ie 3 translations and 2 rotations.

Cv=DOF/2*R/M Cp=(DOF+2)/2*R/M

R=universal Gas Constant 8.314[kJ/kg/K] M=mollecular Weight [kg/kmol]

So let us try this for Argon, DOF=3, M=39.94[kg/kmol]

Plug it in and get 0.527[kJ/kg/K]

compare to Reynold's and Perkins, "Engineering Thermodynamics" talbe B-6b 0.523[kJ/kg/K]

Similarly k=Cp/Cv=3/5=1.67

Try it out for nitrogen and oxygen and you will get pretty good comparison as well, ie k=1.4! So as a first approximation it works quite well for monatomic and diatomic gasses.

Regards,

BAK_FLOW


All times are GMT -4. The time now is 02:57.