If you are a ketchup manufacturer then maintaining your ketchup at the right consistency is a primary concern - same goes for ketchup connoisseurs. A new procedure developed by Bandulasena, et al at the University of Sheffield combines a simple experimental observation and Computational Fluid Dynamics (CFD) to characterize the viscosity of a non-Newtonian fluid, such as ketchup, so we can be confident that our ketchup will flow.

Caedium Free Surface CFD Simulation for a Non-Newtonian Fluid

Non-Newtonian Fluids

Unlike Newtonian fluids (e.g., water) that maintain a constant viscosity at a given temperature, ketchup is a non-Newtonian fluid, so its viscosity reduces as the ketchup flows - e.g., once you shake a ketchup bottle to get the ketchup flowing, it will continue to flow. Getting just the right ketchup consistency is tricky without a quick method to characterize the viscosity of the ketchup. Enter Bandulasena et al with a novel combination of a simple rheology experiment and CFD simulation.

Recipe

• Experiment:
  • Take a sample of the ketchup
  • Seed the ketchup with tiny particles
  • Record the progress of the particles around a specially-shaped small channel
• Simulation:
  • Run a series of CFD simulations for the same channel
  • Vary the power-law non-Newtonian viscosity parameters

Select the best match between the CFD simulation and the observed particle paths to give you the power-law viscosity relationship you seek. Use liberally to keep your ketchup just right.

Notes

• Source: Sticky fingers, The Economist, Technology Quarterly: Q4 2011
• Paper: H C Hemaka Bandulasena, William B Zimmerman and Julia M Rees, An inverse method for rheometry of power-law fluids, Measurement Science and Techonology, Volume 22, Number 12, October 2011
• To simulate non-Newtonian flow in Caedium Professional set Substance->Properties->Phase->Transport->Viscosity Model to either Cross Power Law or Bird Carreau