Viscosity constant of a cylinder

[rayman123]

Homework Statement

Does something like a viscosity constant of a cylinder exist? We are talking about an empty barrel rolling on a horisontal plane and the air friction.
On the classes we got something like this
$$c= 1.76h\cdot r$$ where h is the barrel's height and r is the radius. How to find that formula? are there any tables for this? where did they get 1.76 from?

Thanks

Homework Equations

The Attempt at a Solution

 

[Chestermiller]

Does anyone know what c stands for in this post?