viscosity coefficient

I think there are different viscocity coefficient for microscale and macroscale.Because the forces with primary effection are different.
But I cannot see the difference in some models.
I am new in the LBM field,and maybe have some misunderstands.


could you please explain in more detail what you mean? It is not clear to me what you want to say.


I am sorry.
I want to express that the flow in a big cavity and a microchannel are different for surface tension not being considered in macroscale.I think that there are diffeerent phenomenon between macroscale and microscale.
Thanks again!

Yes, you are right. In the nano- or microscale, you have to take into account surface tension effects if you have free surfaces. If the typical length in your system is smaller than the capillary length, the fluid is usually dominated by surface tension rather than by gravity.
However, the fluid viscosity is the same in both systems.