# Dynamic Viscosity

on . Posted in Dynamics

Dynamic viscosity, abbreviated as $$\mu$$ (Greek symbol mu), also called absolute viscosity, is the force required to move adjacent layers that are parallel to each other at different speeds.  The velocity and shear stress are combined to determine the dynamic viscosity.

## Dynamic viscosity formula

$$\large{ \mu = \frac {\tau} {\dot {\gamma}} }$$

$$\large{ \mu = \frac{ \rho \; v \; l_c }{ Re } }$$

Symbol English Metric
$$\large{ \mu }$$  (Greek symbol mu) = dynamic viscosity $$\large{\frac{lbf-sec}{ft^2}}$$ $$\large{ Pa-s }$$
$$\large{ l_c }$$ = characteristic length or diameter of fluid flow $$\large{ft}$$ $$\large{m}$$
$$\large{ \rho }$$  (Greek symbol rho) = density of fluid $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ Re }$$ = Reynolds number $$\large{dimensionless}$$
$$\large{ \dot {\gamma} }$$  (Greek symbol gamma) = shear rate $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ \tau }$$  (Greek symbol tau) = shear stress $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ v }$$ = velocity of fluid $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$

Tags: Viscosity Equations