Viscous Damping

• Viscous damping model is most common; here, the damping force is taken to be proportional to the velocity across the damper, acting in the direction opposite to that of the velocity.
  
  
• Linear damping force is represented by a viscous dashpot, which shows a piston moving relative to a cylinder containing a fluid. The ideal linear relationship between the force and the relative velocity holds good so long as the relative velocity is low, ensuring a laminar fluid flow.

Figure 8.1: Viscous damper

From fiig. 8.1, the external force that balances the damping force may be expressed as

	(8.1)

where c is called the viscous damping coefficient.