Rheology

When Accretionary Wedge prompted for favourite geology words, I finally had to contribute to the distributed collaborative geoscience blog: Rheology.

Landslides are heterogeneous.

Landslides are heterogeneous.

Rheology is the study of flows. In geophysics, rheological studies usually focus on lava, debris flows, and landslides: materials that ooze and squish and deform without being, strictly speaking, liquids. It’s frequently difficult to establish rheological properties in geology, as the fluids (or fluid-like) flows are dangerous to approach, heterogeneous, and may have scale- or velocity-dependent characteristics that make it difficult to reproduce the properties in a laboratory environment.

The word dates back to the 1920s, constructed from rather obvious Greek roots, translating literally as “study of flow.” The classic quote every rheological society eventually pulls for its motto is from Heraclitus of Ephesus:

Everything flows and nothing abides; everything gives way and nothing stays fixed.

Etymologically, rheology is quite dull.

The reason I absolutely adore rheology is because it’s an exact inverse of orbital mechanics. While orbital mechanics features absolutely gorgeous, elegant mathematics for relatively straightforward, dull-to-observe outcomes, fluid dynamics has horrible, incomplete, ugly mathematics to describe amazingly beautiful outcomes. Rheology is the “is this really necessary?” complication that encompasses fluid dynamics and expands to embrace all those strange borderline-fluid-like deforming, sliding, flowing materials that purists ban from fluids for not technically being liquids.

Rheology is perfect for cocktail physics demonstrations (along with typical density, non-Newtonian fluids, and other food-based demos) for science outreach. The best part? A well-stocked bar can provide all the necessary components for interesting rheological experiments without needing to tuck extra equipment into my purse in advance, allowing for impromptu guerrilla science education whenever the mood strikes.

Related Reading

Origins of Rheology
Liquid Helium, a zero-viscosity superfluild
USGS Debris Flow Dynamics 1, 2, & 3
Alcohol evaporating through cream, a video of the classic bar-demonstration.

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5 Responses to Rheology

  1. When applied to Drilling Fluids, Rheology deals with the relationship between Flow Rate and Flow Pressure and their combined effects on the Flow Characteristics of the fluid (drilling mud).

  2. Pingback: Stuff we linked to on Twitter last week | Highly Allochthonous

  3. Jim DeLaHunt says:

    I think there’s a typo in the link under the text “cocktail physics demonstrations”. The HREF target URL is missing the “http://” at the beginning. The web server helpfully fills in “http://www.geomika.com/” etc., which is of course completely wrong. Clicking on this link thus gives an error 404.

    As a convenience, here’s the URL with the missing part: http://www.eos.ubc.ca/~mjelline/teaching%20stuff/maitaieddemoweb.pdf . An interesting read!

  4. christie says:

    Hey what about solids? Rheology is, more generally, the relationship between stress and strain.

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