When calculating Reynolds number, when do I use dynamic/kinetic viscos

[PhyIsOhSoHard]

When calculating Reynolds number, when do I use dynamic viscosity and when do I use kinematic viscosity?

In a pipe with air flowing inside it, what would you use when calculating Reynolds number and why?

 

[Chestermiller]

When calculating Reynolds number, when do I use dynamic viscosity and when do I use kinematic viscosity?

In a pipe with air flowing inside it, what would you use when calculating Reynolds number and why?

The Reynolds number contains the density in the numerator and the dynamic viscosity in the denominator. The kinematic viscosity is equal to the dynamic viscosity divided by the density. So, if you know the dynamic viscosity and the density, you can calculate the kinematic viscosity. So, in practice, you use whichever is more convenient / available.