Piping Systems FluidFlow3 - Non-Newtonian Flow

A non-Newtonian fluid is a liquid whose flow properties are not described by a single constant value of viscosity. Examples of non-Newtonian fluids are: polymer solutions, starch suspensions, paint, blood, food products, and mining suspensions of densely packed particles.

The relation between the shear stress and the strain rate can be either linear or nonlinear. This means that, for fluids exemplifying a nonlinear characteristic, a constant coefficient of viscosity cannot be defined. FluidFlow allows you to describe this relationship of shear-dependent viscosity, according to any of the following rheology models:

• Bingham Plastic
• Power Law
• Herschel-Bulkley
• Casson

Medical Instrumentation Modelling – Blood Flow

The FluidFlow3 non-Newtonian, non-settling slurry flow module has also been used to successfully model blood flow (µl/s) through medical/laboratory instrumentation equipment consisting of micro-bore tubing. Our customers have been able to analyse and optimise system performance and develop a detailed study of system operating profiles including pressures, pressure losses, viscosities, flow rates etc. This has enabled our customers to improve existing system performance and examine alternative and improved system design scenarios. FluidFlow3 allows the user to select from four rheology models: Power Law, Casson, Bingham Plastic and Herschel Bulkley. The Power Law & Casson models are often applied to blood flow. An advantage of FluidFlow3 is that, the user simply defines the shear-stress vs. shear-rate rheology data and you can simply switch between the available rheology models to establish the best curve-fit, hence ensuring maximum accuracy. When modelling blood flow, it is important to have an appreciation of the effects of hematocrit on blood viscosity. The screenshot on the left provides an illustration of a sample blood system model. Click here to view an illustration of blood rheology which has been fitted to a Power Law curve.

Power law modelling of rheology data

The example to the left shows viscometer data for a non-Newtonian fitted to a Power Law relationship.

FluidFlow3 uses different friction factor relationships for each available model, the relationships are valid over all flow regimes.