viscosity

The extent to which the fluid resists flow under applied forces, measured by dividing the tangential friction per unit area by the velocity gradient under streamline flow conditions.

Resistance to material flow For example, water is less viscous than molasses, making it easier to flow. It will be appreciated that viscosity is related to the concept of shear forces and that different fluid layers exert shear forces on each other or on other surfaces as they move relative to each other. Viscosity is behind the frictional components of the skin. ♦ Kinematic viscosity is a measure of the rate at which momentum passes through a fluid. It is measured in Stokes. ♦ Dynamic viscosity is the ratio of the stress in the fluid region to the rate of change in the strain it undergoes. It is equal to kinematic viscosity multiplied by fluid density. It is measured in Pascal seconds or Poise

Depending on the application, kinematic viscosity is more convenient than absolute or dynamic viscosity. Kinematic viscosity is the absolute viscosity of a fluid divided by its mass density. The magnitude of the kinematic viscosity is the area divided by the time, the appropriate unit is square meters per second. A unit of kinematic viscosity in the centimeter - gram - second (CGS) system known as Stokes in the UK and Stokes in the United States. It is from British physicist Sir George Gabriel Stokes. Give your name. The stroke is defined as 1 square centimeter per second

Actually there are two quantities called viscosity. The amount defined above may be referred to as dynamic, absolute or simple viscosity to distinguish it from other quantities, but in many cases it is called viscosity. Another quantity called kinematic viscosity (represented by the Greek letter ν "nu") is the ratio of the viscosity of the fluid to its density. Kinematic viscosity is a measure of the resistance flow of a fluid under the influence of gravity. It is usually measured using a device called a capillary viscometer - basically a calibrated can with a thin tube at the bottom. When two equal volumes of fluid are placed in the same capillary viscometer and flow under the influence of gravity, it takes time for the more viscous fluid to flow through the tube than the non-viscous fluid. Capillary viscometer is explained in detail later in this section.

The fluid flowing through the stationary surface undergoes a force countering the flow. This tendency to resist flow is known as the viscosity of the fluid. Fluids such as air have low viscosity, thicker fluids like water are more viscous, fluids such as honey and oil are more viscous. Viscosity represents the internal flow resistance of a fluid and can be regarded as a measure of fluid friction. The higher the viscosity of the liquid, the slower the flow rate. Viscosity can be measured by calculating the time required for a given amount of liquid to flow through the capillary under gravity. The more viscous liquid, the more time it takes. The viscosity can also be determined by measuring the rate at which the steel ball falls into the liquid. As the viscosity increases, the sphere descends more slowly. Viscosity is related to the relative mobility of individual molecules of a liquid relative to each other.