Viscous damping

In continuum mechanics, viscous damping is a formulation of the damping phenomena, in which the source of damping force is modeled as a function of the volume, shape, and velocity of an object traversing through a real fluid with viscosity.

Typical examples of viscous damping in mechanical systems include:

• Fluid films between surfaces
• Fluid flow around a piston in a cylinder
• Fluid flow through an orifice
• Fluid flow within a journal bearing

Viscous damping also refers to damping devices. Most often they damp motion by providing a force or torque opposing motion proportional to the velocity. This may be affected by fluid flow or motion of magnetic structures. The intended effect is to improve the damping ratio.

• Shock absorbers in cars
• Seismic retrofitting with viscous dampers
• Tuned mass dampers in tall buildings
• Deployment actuators in spacecraft

Single-degree-of-freedom system

In a single-degree-of-freedom system, viscous damping model relates force to velocity as shown below:

$f=c{\dot {x}}$

Where $c$ is the viscous damping coefficient with SI units of $N\cdot s/m$. This model adequately describes the damping force on a body that is moving at a moderate speed through a fluid. It is also the most common modeling choice for damping.

See also

• Hysteresis
• Coulomb damping