![]() This measurement is most commonly employed for Newtonian liquids, which do not change viscosity in response to applied force (shear rate). When should Kinematic Viscosity Measurements be used? The dynamic viscosity measurement is most useful for liquids that vary their apparent properties as force or pressure is applied. When you want to know a fluid's internal resistance, or the force necessary to transfer one plane of the liquid over another, you apply/test dynamic viscosity. When should Dynamic Viscosity Measurements be used? Stokes and Poise appear to have received the same answer, but in two distinct ways. Absolute viscosity is calculated by dividing kinematic viscosity by fluid density. ![]() What does Kinematic viscosity signify? When to use kinematic viscosity?ĭynamic viscosity is a force measurement, whereas kinematic viscosity is a velocity measurement. The property of a fluid that provides resistance to the transport of one layer of fluid over an adjacent layer is called viscosity. Viscosity is a physical property that describes how well simple fluids flow. Fluid density is included in the measurement of kinematic viscosity. This signifies that the fluid's density or weight aids its flow. The fluid is not being pushed by any external force. It's the length of time it takes for a known amount of fluid to flow a certain distance. A centipoise is one hundredth of a poise, or one millipascal-second (mPa⋅s) in SI units (1 cP = 10−3 Pa⋅s = 1 mPa⋅s)ġ centistoke (cSt) equals 1 millimetre squared per second (mm2/s) is the formula for kinematic viscosity. The dynamic viscosity is measured as poise. Centipoise (cP) is recommended for easier readings. The force required to make it flow is used to assess internal friction, which has been given the name poise. Internal friction in various fluids is overcome by an external force in order for them to flow. When individuals talk about viscosity, they're usually referring to either kinematic or dynamic viscosity. These phrases are generated from the measurement of viscosity. ![]() In actuality, the term "viscosity" encompasses a number of diverse concepts. It is used to define the thickness of a product or how well it flows. I have many collaborators in these efforts, including Richard Craster and Richard Kerswell.Viscosity appears to be a straightforward idea at first view. Much of my work is theoretical, focussing on mathematical modelling, but I also do experiments (some of which took place in the backyard and cellar occasionally even in a lab). However, the underlying idea (the reduction of governing equations to simpler, useful models) is a powerful tool that can be brought to bear in these applications also. These materials are mostly granular media, and require a different physical framework. Similar models are also used for landslides, avalanches, and the dynamics of sand. The rheology of mud and ice has several similarities with that of lava, and the same non-Newtonian fluid models can be used to describe how they flow. Related geological problems include mud flows and glacier mechanics. But by using asymptotic methods, simpler versions can be built for use by geologists. Computations with the full three-dimensional equations is an inefficient route for such a model, partly because the rheology of cooling lava is so complicated. That is, a general theoretical model that incorporates the essential physical ingredients and can be used to compute the flow of lava under terrestrial and extra-terrestrial conditions. For example, for lava flow, the main goal is to develop a "shallow-lava theory". My work in this area is focused on simplifying these equations to gain insight into the flow dynamics. Unfortunately, fluid models that build in the rheology significantly complicate the governing equations. In lava, for example, the microstructure is provided by a network of interlocked silicate crystals, and endows the fluid with an internal strength that allows lava to withstand a certain amount of imposed stress before it flows. Often, the 'rheology' arises because the fluid in question builds up a microstructure at the molecular level which becomes sufficiently extensive to affect the macroscopic properties of the fluid. Aside from air and water, most of the fluids we encounter in physical and industrial processes are "non-Newtonian" (meaning that there is no simple relationship between the stress and the rate of strain).
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