![]() It appears Stokes and Poise got the same answer just in two different ways. If you divide kinematic viscosity by the fluid density, you get absolute viscosity. Thus, dynamic viscosity is a measure of force, while kinematic viscosity is a measure of velocity. Kinematic viscosity incorporates fluid density as part of its measurement. calculates the kinematic viscosity by dividing the dynamic viscosity by the gas. finds the density of the gas with the Ideal Gas Law. helium at 273K has a viscosity of 1.9 x 10 -5 Pa s, with a Sutherland Constant of 79.4 K. This means the fluid’s weight or density helps it to flow. For example, air at 323 K has a viscosity of 1.716 x 10 -5 Pa s, with a Sutherland Constant of 110 K. There is no external force pushing the fluid. It is the time it takes to have a known amount of fluid flow a given distance. The formula for kinematic viscosity is 1 centistoke (cSt) equals 1 millimeter squared per second (mm 2/s). This viscosity measurement was given the term kinematic. Again, centistokes (cSt) is used for easier readings. These tests led to Stokes’ law and a different form of viscosity measurement. He tested this theory by putting fluid in a glass tube and measuring how long it took for the fluid to flow a certain distance. Stokes surmised there was some type of internal friction in the fluid causing the different rates of falling. He discovered that the same particle sank at different rates in different fluids. Therefore, this type of viscosity measurement requires an external force in order to be measured.Ībout the same time Poise was performing his tests, an Irishman named Sir George Stokes was dropping particles into fluids and measuring how fast they fell to the bottom. Pascal is a unit of force just like horsepower. The formula for dynamic or absolute viscosity is 1 centipoise (cP) equals 1 millipascal-second (mPa-s). The term dynamic or absolute is used for this viscosity measurement. To make readings easier, centipoise (cP) is preferred for lubricant viscosities. This internal friction is measured by the force needed to make it flow and was given the measurement name of poise. This led him to conclude that different fluids have an internal friction which must be overcome by an external force in order to flow. The kinematic viscosity formula is expressed as, /. It is the ratio of the area of time henceforth it is m22/s or ft22/s. It is the ratio of the dynamic viscosity to its density, a force independent quantity. Poiseuille found that different blood flowed at different speeds through the glass tubes with the same amount of force. The units of kinematic viscosity are established on time and area. This article explains the differences.Īround 1840, a French mathematician named Jean Leonard Marie Poiseuille conducted tests involving the flow of blood through small glass tubes. This resistance is measured by two different methods. The definition of lubricant viscosity is the fluid’s resistance to flow and shear. Fill in zero (0) in the weight percent column (Wt%) if Base oil #3 and-or Base oil #4 are not part of the mixing viscosities.Viscosity is the utmost characteristic of a lubricant. You can use this calculator to predict mixing viscosities of 2-4 base oils. Viscosity temperature is not required but must be the same for all base oils viscosities. Fill in zero 0 (or leave default “0”) in Wt % if not included in the blending calculations. Please note: Leave the default value of “1” in the viscosity field if blending less than two liquids. ![]() If you don’t want to include 3rd and 4th base oils, fill any value (>1) in the viscosity cell and zero (0) in the Wt%.Ĥ- Repeat the same for Base Oil #4 by filling in the viscosity and Wt% of the Base oil.ĥ- Click Calculate to predict the mixing viscosity of the blend. Viscosity Calculator #3ġ- Fill the viscosity of Base oil #1 and weight percent (Wt%) in the third (Wt%) column.Ģ- Fill in the viscosity of Base Oil #2 and weight percent (Wt%) in the next column.ģ- Fill in the weight percent (Wt%) and Base oil #3 viscosity in the 3rd row. Module #3: Mixing viscosities calculator to blend or mix more than two base fluids.
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