Viscous Damping

Occurs when a body moves through a fluid.
Using damper (e.g., COMBIN14) is one of the ways to model this behavior.
The damping force is proportional to velocity. The proportionality constant c is called the damping constant.
Also quantified as damping ratio (x, ratio of damping constant c to critical damping constant c_c).
Critical damping is defined as the threshold between oscillatory and non-oscillatory behavior, where damping ratio x = 1.0
For the free vibration of a SDOF system

Occurs when a body moves through a fluid.