Characteristic velocity of Hooke contact model

I've been looking for some documentation on the "characteristic" velocity used in the Hooke contact model. I have a simulation that is essentially a hopper filling/draining problem, but I also have the particles fall on and impact different surfaces once they leave the hopper. Thus, I have 2 different characteristic velocities in my simulation:

1. The very low velocities present in the hopper
2. The relatively higher velocities the particles have when they strike the surfaces outside the hopper.

I currently have my characteristic velocity set to a value that is somewhere in between those 2 extremes. I understand what the term does in the mathematical model, but is there any sort of guidelines on selecting a characteristic velocity to use in a DEM simulation? Should the value be chosen to account for the greatest number of collisions (which I assume to be the low speed "collisions" in the hopper), or should it be chosen to account for the higher velocity impacts? Or does it not really matter, as long as the characteristic velocity is somewhere within the range of velocities expected in my problem (i.e. nothing crazy fast like 1000 m/s)?

For reference, I expect the bulk of my collisions to take place between 0-1 m/s, with many more collisions taking part at the lower end of the scale. Thus, I have my characteristic velocity set to .01 m/s.

Any sources, papers, or personal experience would be extremely helpful!