Thixotropy is a property of fluids that become less viscous when subjected to stress, returning to their semi-solid state when deformation stops. It can pose safety risks in engineering and affect industries such as oil and gas and food. Understanding thixotropy is important for predicting fluid behavior and exploring ways to exploit this property.
Thixotropy is a property exhibited by some fluids that have a gel-like consistency when stationary, but thin when subjected to shear stresses. One of the classic examples of thixotropic fluid is quicksand. As long as it’s undisturbed, the sand will be relatively thick. Once something falls and starts wiggling, putting stress on the quicksand, it becomes more liquid. Besides worrying people about falling into quicksand pits, thixotropy is a property that can be used in many interesting ways.
A thixotropic fluid will become less and less viscous as it is subject to stresses such as churning, agitation or agitation. As soon as the deformation stops, the fluid will regain its viscosity, slowly returning to the semi-solid state. This is in contrast to a rheopectic fluid, which will experience increasing viscosity as it is agitated; a mixture of cornstarch and water, for example, will be gelatinous at rest but will firm up under pressure. Cornstarch and water are sometimes used in science lessons to introduce students to the concept with a fluid they can feel and manipulate.
Engineers need to think about thixotropy when designing structures because some substrates can be thixotropic. For example, when engineers build structures on reclaimed land, the underlying clays can be subject to liquefaction during an earthquake, posing a safety risk. While it is possible to build on clays and thixotropic soils, care must be taken to ensure safety, with the structure anchored to a substrate that does not liquefy during deformation, such as bedrock.
Drilling fluids used in the oil and gas industry can also be thixotropic in nature. The fluids will remain relatively solid when stopped, but will liquefy as they are used during drilling to act as lubricants. Thixotropy also affects people who work with clays, such as potters, and in some areas of the food industry. Some foods have properties such as thixotropy that can interfere with the way they are handled and processed.
Engineers who study fluid mechanics have a variety of explanations for how thixotropy works, depending on the fluid involved and the types of forces it is subjected to. Understanding this property can be important for people working with thixotropic fluids, as it will allow them to predict fluid behavior and explore ways in which this property can be exploited.
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