# Viscosity Coefficient

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Viscosity coefficient, abbreviated as $$\eta$$ (Greek symbol eta), also called coefficient of viscosity, is the tangential friction force required to preserve a unit velocity gradient between two parallel layers of liquid of unit area.  The greater the coefficient of viscosity the greater the force required to move the layers at a velocity.

### Viscosity Coefficient Formula

$$\large{ \eta = \frac { F_t \; l } { A \; v } }$$

Where:

$$\large{ \eta }$$  (Greek symbol eta) = viscosity coefficient

$$\large{ A }$$ = area

$$\large{ l }$$ = distance between the layers

$$\large{ F_t }$$ = tangential force

$$\large{ v }$$ = velocity

Solve for:

$$\large{ F_t = \eta \; \frac { A \; v } { l } }$$