Hi everybody,

I’m now studying single-phase & triple-component LBM and code is almost done, but I’ve got trouble about value of tau. In my code, tau is calculated by kinematic viscosity, and it is undeniably fact. Result of calculation with species property, values of tau are about 0.8, 1.03, 1.2(H2O, N2, O2, in order). With conditions that I concern, though, calculation reachs just 2195 steps and stop because of negative density value of N2.

I suddenly hit upon the paper which mentioned about tau that, “value of tau were set to be unity for stability”. I apply it to my code, now it works 75000 steps and still working, amazingly!!

So… my question is…

This is CORRECT?? If it is, why? Changing value of tau means that value of kinemativ viscosity become difference and will not equivalent with real property. Can it be suitable…?

Please, help me

best regard,

K. N. KIM

P.S.

- Base of my model is paper of Luo and Girimaji[Phys. Rev. E 67, 036302(2003)] and McCracken and Abraham[Phys. Rev. E.71,046704(2005)]
- I’m really thankful for this forum. Really helpful to me