How Does Velocity Affect Viscosity in Material Flow?

[Sahir Butt]

As I understand, viscosity characterizes the "resistance" of a material to "flow locally" as a function of the velocity of the material flow.
Now my question is following, what are the physical mechanisms involved which make this "resistance" dependent on velocity of the material movement/flow?
If the atomic interactions are a function of positions/displacement of atoms/material points... Where is this velocity dependence coming from??

 

[Chestermiller]

It is not dependent on the velocity. It is dependent on the spatial velocity gradient. To get an understanding of how the atomic interactions come into play, see Chapter 1 of Transport Phenomena by Bird, Stewart, and Lightfoot.