volume viscosity (dilatational viscosity)

https://doi.org/10.1351/goldbook.V06650
A quantity ζ which enters into equations at any point where the flow involves a change in volume, i.e. is dilatational. If the deformation is purely dilatational, the average of three normal stress components is: σ=13 (σxx+σyy+σzz)=−p+ζ (∂vx∂x+∂vy∂y+∂vz∂z) where p is the hydrostatic pressure at the point considered in the absence of motion.
Source:
PAC, 1979, 51, 1213. (Terminology and Symbols in Colloid and Surface Chemistry Part 1.13. Definitions, Terminology and Symbols for Rheological Properties) on page 1216 [Terms] [Paper]
Citation: 'volume viscosity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.V06650 RIS BibTex EndNote
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