For articles and white papers pertaining to General Viscosity, Our scientists contribute to industry knowledge by authoring papers in various technical publications. Intrinsic viscosity reflects the capability of a polymer in solution to enhance the viscosity of the solution. Intrinsic Viscosity (): The ratio of a solution’s specific viscosity to the concentration of the solute, extrapolated to zero concentration. Measured in stokes (St) or centistokes (cSt). Also known as the coefficient of kinematic viscosity. Kinematic Viscosity: The absolute viscosity of a fluid divided by the density of the fluid. Also known as coefficient of viscosity.Īpparent Viscosity: The value obtained by applying the instrumental equations used in obtaining the viscosity of a Newtonian fluid to viscometer measurements of a non-Newtonian fluidĭilute Solution Viscosity: The viscosity of a dilute solution of a polymer, measured under prescribed conditions, is an indication of the molecular weight of the polymer and can be used to calculate the degree of polymerization. These manual glass viscometers require the use of a Constant Temperature Bath in order to stabilize the sample temperature for measurement.Ībsolute Viscosity: The tangential force per unit area of two parallel planes at unit distance apart when the space between them is filled with a fluid and one plane moves with unit velocity in its own plane relative to the other. Most laboratory instruments use glass capillaries or "tubes". There are several standardized capillaries in use. The more viscous an oil, then the longer it takes to flow via a capillary under the influence of gravity alone. Generally, measurements made using capillary viscometers rely on the relation between time and viscosity. The most common method for measuring kinematic viscosity is the use of a gravimetric capillary (Figure 1) that is usually temperature controlled at 40 ☌ and 100 ☌ for multigrade oils, and 40 ☌ for single grade oils. Newton’s Law of viscosity is defined as shear stress on a layer of the fluid element that is directly proportional to the rate of shear strain.Video courtesy of Ekeeda - Measuring Kinematic Viscosity ‘ν’= Viscosity/Density Newton’s Law of viscosity Kinematic viscosity is defined as the ratio of dynamic viscosity and density of the fluid. Similarly, the viscosity of gases decreases with a decrease in temperature while the viscosity of liquid increases with a decrease in temperature. The viscosity of gases increases with an increase in temperature while the viscosity of liquid decreases with an increase in temperature. The temperature on viscosity has a direct effect. So, μ = dyne-sec/cm 2 Effect of Temperature on viscosity In CGS, force is represented by dyne and time is represented in seconds and mass is represented in cm. In MKS, force is represented by kg-f and time is represented in seconds and mass is represented in m. = Shear Stress / (Change of Velocity/ change of distance)īy solving this equation for units, we will get (Force x Time) / (Length) 2 We know, that Viscosity = Shear Stress/Shear strain Units of viscosity can be calculated as below: Viscosity is the property of the fluid which offers the resistance of one layer of fluid to the adjacent layer of the fluid. S (for Gases) = Weight density of Gases/Weight density of Air Viscosity S (for liquids) = Weight density of liquid/Weight density of water It is also called Relative density and is denoted by ‘S’. Specific Gravity is defined as the ratio of weight density of the liquid to weight density of water in the case of liquids and weight density of the gases to weight density of air in the case of gases. W= (mass of fluid x g)/ Volume of fluid = ρ x g Specific Gravity W= Weight of fluid/Volume of fluid = Acceleration due to gravity * mass of fluid/ Volume of fluid Weight density or Specific weight of a fluid is defined as the ratio of the weight of the fluid to the volume of fluid and it is denoted by ‘w’. Hence, we can also say that the Specific volume of a fluid is the reciprocal of the mass density of the fluid. Specific Volume= Volume of fluid/mass of fluid = 1/(Mass of fluid/volume) = 1/ρ Specific Volume of fluid is defined as the volume of a fluid per unit mass of fluid. The density of water is 1gm/cm 3 or 1000kg/m 3. The density of the fluid is considered contact while the density of the gases tends to change with the temperature and pressure. Mathematically, the density or mass density of the fluid is written as:
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