Thixotropy is the property of some non-newtonian pseudoplastic fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear, the lower its viscosity. However, this is not a universal definition; the term is sometimes applied to pseudoplastic fluids without a viscosity/time component. A non-Newtonian fluid is a fluid in which the viscosity changes with the applied shear force. ... A Power-law fluid is a type of Generalized Newtonian Fluid for which the shear stress, τ, is given by where: K is the flow consistency index (SI units Pa•sn), ∂u/∂y is the shear rate or the velocity gradient perpendicular to the plane of shear (SI unit s... In physics and mechanics, shear refers to a deformation that causes parallel surfaces to slide past one another (as opposed to compression and tension, which cause parallel surfaces to move towards or away from one another). ...

Many gels and colloids are thixotropic materials, exhibiting a stable form at rest but becoming fluid when agitated. Some clays are also thixotropic, with their behavior of great importance to structural engineering in earthquake zones. Clayey ground can practically liquefy under the shaking of a tremor, greatly increasing the effect on buildings. A gel (from the lat. ... A colloid or colloidal dispersion, is a form of matter intermediate between a true solution and a mixture (suspension). ... Clay is a generic term for an aggregate of hydrous silicate particles less than 4 μm (micrometres) in diameter. ... Structural engineering is the field of civil engineering particularly concerned with the design of load-bearing structures. ... Global earthquake epicenters, 1963–1998 An earthquake is a trembling or a shaking movement of the Earths surface. ... Soil Liquefaction is the process by which saturated, unconsolidated soil or sand is converted into a suspension. ...

The classic example of a thixotropic fluid is ketchup, where waiting for it to pour can be more effective than pounding on the bottom of the bottle. Thixotropic compounds are important paint additives, allowing a thick, smooth application that doesn't run. Organic Ketchup, a 21st century condiment Ketchup (or catsup) is a popular condiment, usually made with ripened tomatoes. ...

Fluids which exhibit the opposite property, in which shaking for a time causes solidification, are called rheopectic and are much less common. Rheopecty is the property of some non-newtonian fluids to show a time dependant change in viscosity; the longer the fluid undergoes shear, the higher its viscosity. ...

See also

• Non-Newtonian fluid
• Power-law fluid

A non-Newtonian fluid is a fluid in which the viscosity changes with the applied shear force. ... A Power-law fluid is a type of Generalized Newtonian Fluid for which the shear stress, τ, is given by where: K is the flow consistency index (SI units Pa•sn), ∂u/∂y is the shear rate or the velocity gradient perpendicular to the plane of shear (SI unit s...

References

• Reiner, M., and Scott Blair, Rheology terminology, in Rheology, Vol. 4 pp. 461, (New York: Achedemic Press, 1967)