Ketchup with your CFD?

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 FluidCaedium 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.


  • 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.