Dynamic Viscosity comes into play when we talk about the internal resistance in fluid among its neighbouring particles under an external force other than the gravitational force. Kinematic Viscosity comes into play when we talk about the overall flow of fluid under gravity only. Viscosity also finds applications in manufacturing printing ink. It is a characteristic when choosing the cooking oil, that directly affects our health. The coefficient of viscosity is also maintained in them so it can be easy to apply to the walls. Viscosity also plays an important role in the manufacturing of paints and varnishes. It also finds the applications in the pharmaceutical industry in the manufacturing of medicines like cough syrup. The coefficient of viscosity is used to calculate the molecular weight of organic liquids. The knowledge of viscosity helps us to understand which lubricant or oil is suitable for machines and engines. This means dynamic viscosity is also directly related to density. We observe that kinetic viscosity is inversely related to density which means if the density is increased the kinetic viscosity decreases and vice versa.įrom the above equation, we conclude that kinetic viscosity has a direct relation with dynamic viscosity and an inverse relation with density. Y is a shearing rate change Relation of Kinetic and Dynamic Viscosity with Density Mathematically, the viscosity is estimated by the given formula In liquids, generally, it increases with temperature and in gases, decreases with temperature. Viscosity differs with temperature for a given fluid. Viscosity is of two types kinematic viscosity and dynamic viscosity. A given temperature and pressure are characteristic of a given fluid. It arises due to the interactions between the entities of fluids. In fluids (liquid or gas), resistance (or friction) to flow is known as viscosity. Their units, representation, and the relationship between them. Now let's see what is viscosity in detail and what is the difference between kinematic viscosity and dynamic viscosity. In the first case, there is Kinematic Viscosity When only gravitational force is in action, and in the second case, when you apply an external force by squeezing, dynamic viscosity is in play. But viscosity in play is not the same in both cases. This is because ketchup is also very thick. And while pouring ketchup from the bottle, it takes more time to flow and needs an extra instantaneous force (by squeezing or squirting). The temperature must be defined to interpret the viscosity reading.If you have ever tried to take out honey by keeping the bottle upside down, it feels thick. Likewise, reporting viscosity for trending purposes without a reference to temperature is nonsensical. Viscosity is not a dimensional measurement, so calling highly viscous oil thick and less viscous oil thin is misleading. Sometimes, viscosity is erroneously referred to as thickness (or weight). Generally speaking, viscosity is a fluid’s resistance to flow (shear stress) at a given temperature. Given the importance of viscosity analysis coupled with the increasing popularity of onsite oil analysis instruments used to screen and supplement offsite laboratory oil analysis, it is essential that oil analysts understand the difference between dynamic and kinematic viscosity measurements. By contrast, most onsite viscometers measure dynamic viscosity, but are programmed to estimate and report kinematic viscosity, so that the viscosity measurements reported reflect kinematic numbers reported by most labs and lube oil suppliers. Most used oil analysis laboratories measure and report kinematic viscosity. The two are easily confused, but are significantly different. Viscosity can be measured and reported as dynamic (absolute) viscosity or as kinematic viscosity. ![]() ![]() However, there is more to viscosity than meets the eye. Likewise, there is no property more critical to effective component lubrication than base oil viscosity. ![]() Of all the tests employed for used oil analysis, none provides better test repeatability or consistency than viscosity. Viscosity reporting is only valid when the temperature at which the test was conducted also is reported - for example 23 cSt at 40 degrees C. ![]() This value is converted to standard units such as centistokes (cSt) or square millimeters per second. It is determined by measuring the time in seconds, required for a fixed volume of fluid to flow a known distance by gravity through a capillary within a calibrated viscometer at a closely controlled temperature. Kinematic viscosity is a measure of a fluid's internal resistance to flow under gravitational forces.
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