![]() ![]() * The viscosity given is indicative of the viscosity RANGE of the material in a static state. Loosely defined as “flow properties”.Īpproximate viscosities of common liquid and semi-solid materials at 70º F: Low TI materials generally require the use of pressure supplied by ram pumps to move them into a metering system. If the specification for the material includes a thixotropic index, one can tell how easily or how hard it will be to move. This is a term loosely applied to a wide range of materials and can include those that will self-level as well as those which do not. These types of fluids are not generally well suited to use with meter/mix systems. The opposite of thixotropic, namely, the tendency of a fluid to increase in viscosity when subjected to shear, the resistance to flow increasing with the amount of force applied. Pascal is a unit of force just like horsepower. Typical examples are water and oils.ĭilatant Fluid. The formula for dynamic or absolute viscosity is 1 centipoise (cP) equals 1 millipascal-second (mPa-s). Their viscosity remains the same whether at rest or in motion. This unit is used in honor of French physicist, Jean Lonard Marie Poiseuille (1797-1869), who worked with Gotthilf Hagen on the widely known Hagen-Poiseuille law which applies to laminar flow through pipes. Newtonian fluids exhibit neither thixotropy or dilatancy and are referred to as true liquids. The most commonly used unit for dynamic viscosity is the CGS unit centipoise (cP), which is equivalent to 0.01 Poise (P). Example:īrookfield Model RVT, Spindle #5, F. In this case centipoises x 0.000672 lbm/ft sec. Typically, one may be taken at 10 rpm, the second at 1rpm. Sometimes absolute viscosity is given in terms of pounds mass. The higher the difference in the two readings, the more thixotropic the material is, and easier to move. s 1000 cP Absolute Viscosity Definition: 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. At rest, it will not pour, but will flow readily when submitted to shear. This unit is used in honor of French physicist, Jean Lonard Marie Poiseuille. The most commonly used unit for dynamic viscosity is the CGS unit centipoise (cP), which is equivalent to 0.01 Poise (P). Mayonnaise is a good example of a thixotropic fluid. In this page we briefly discuss the most common units for the two main types of viscosity: dynamic and kinematic. The tendency for the viscosity of a liquid to decrease when subjected to shear. ![]()
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