page_title: Capillary breakup rheometry
section_title: Scaling laws
hierarchical_section_title: Capillary breakup rheometry / Scaling laws
caption_attribution_description: English: Profile, scaling law and filament images in capillary breakup
context_page_description: Capillary Breakup Rheometry is an experimental technique used to assess the extensional rheological response of low viscous fluids. Unlike most shear and extensional rheometers, this technique does not involve active stretch or measurement of stress or strain but exploits only surface tension to create a uniaxial extensional flow. Hence, although it is common practice to use the name rheometer, capillary breakup techniques should be better addressed to as indexers.
  Capillary breakup rheometry is based on the observation of breakup dynamics of a thin fluid thread, governed by the interplay of capillary, viscous, inertial and elastic forces. Since no external forcing is exerted in these experiments, the fluid thread can spatially rearrange and select its own time scales. Quantitative observations about strain rate, along with an apparent extensional viscosity and the breakup time of the fluid, can be estimated from the evolution of the minimal diameter of the filament. Moreover, theoretical considerations based on the balance of the forces acting in the liquid filament, allow to derive information such as the extent of non-Newtonian behaviour and the relaxation time.
context_section_description: The behaviour of the fluid determines the relative importance of the viscous and elastic terms in resisting the capillary action. Combining the force balance with different constitutive models, several analytical solutions were derived to describe the thinning dynamics. These scaling laws can be used to identify fluid type and extract material properties.
caption: Temporal evolution of the midpoint filament diameter, scaling laws and high-resolution images of capillary breakup experiments for different fluid. From left: visco-capillary thinning (silicone oil) and elasto-capillary thinning (PEO in water solution)
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