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A single viscosity measurement at a constant speed in a typical viscometer is a measurement of the instrument viscosity of a fluid (not the apparent viscosity). In the case of non-Newtonian fluids, measurement of apparent viscosity without knowledge of the shear rate is of limited value: the measurement cannot be compared to other measurements if the speed and geometry of the two instruments ...
Extensional viscosity can be measured with various rheometers that apply extensional stress. Volume viscosity can be measured with an acoustic rheometer. Apparent viscosity is a calculation derived from tests performed on drilling fluid used in oil or gas well development. These calculations and tests help engineers develop and maintain the ...
Such continuum models tend to be non-Newtonian, since the apparent viscosity of granular flows increases with pressure and decreases with shear rate. The main difference is the shearing stress and rate of shear.
˙ is the apparent shear rate (s −1), σ is the shear stress (Pa), η a is the apparent viscosity (Pa·s), ∆P is the pressure difference between the leading pressure sensor and the last pressure sensor (Pa), Q is the flow rate (ml/s), w is the width of the flow channel (mm), h is the depth of the flow channel (mm),
A Newtonian fluid is a power-law fluid with a behaviour index of 1, where the shear stress is directly proportional to the shear rate: = These fluids have a constant viscosity, μ, across all shear rates and include many of the most common fluids, such as water, most aqueous solutions, oils, corn syrup, glycerine, air and other gases.
Shear thinning in a polymeric system: dependence of apparent viscosity on shear rate. η 0 is the zero shear rate viscosity and η ∞ is the infinite shear viscosity plateau. At both sufficiently high and very low shear rates, viscosity of a polymer system is independent of the shear rate.
The change in apparent viscosity is dependent on the applied electric field, i.e. the potential divided by the distance between the plates.The change is not a simple change in viscosity, hence these fluids are now known as ER fluids, rather than by the older term Electro Viscous fluids.
The dilute gas viscosity contribution to the total viscosity of a fluid will only be important when predicting the viscosity of vapors at low pressures or the viscosity of dense fluids at high temperatures. The viscosity model for dilute gas, that is shown above, is widely used throughout the industry and applied science communities.