A viscous fluid, so when the fluid flow in the pipeline, close to the wall of the fluid will be adhered to the wall, and the center while a certain speed of the fluid flow, so as viscous force, the fluid within the layer To a certain speed of the distribution.

According to Newton's summary: In the fluid movement, block shear deformation of the viscous fluid F and the velocity gradient and the contact area is directly proportional, and the nature of the fluid, its mathematical expression for

F U A 115

In the formula DDFluid perpendicular to the direction of the speed the pace of rate changes;

ADDContact area;

UDDCharacterization of the ratio coefficient of viscous fluid, known as dynamic viscosity or referred to viscosity, units are:Ns / m 2 or(Pas)

Fluid power density and viscosity of U P ratio for the kinematic viscosity v, that is,

V 116

Kinematic viscosity v units are m 2 / s referred to Sri Lanka.