Viscosity Model Panel

AFT Fathom can model systems with Newtonian or non-Newtonian fluids. A Newtonian fluid is one where the fluid viscosity is fixed and independent of fluid velocity, while a non-Newtonian fluid is one where the fluid viscosity is variable and dependent on fluid velocity. Most industrial fluids are Newtonian fluids, although there are important applications for non-Newtonian fluids. By default, AFT Fathom has the Newtonian viscosity model selected.

AFT Fathom offers seven viscosity models:

Modeling non-Newtonian fluids is a complex task. A myriad of theoretical models and test equipment exist, and each have various names unique to an industry or application. Each of the non-Newtonian viscosity models require rheological inputs to be defined. Those inputs are detailed on the pages for each model as well as an explanation as to what the viscosity model is meant for, how to use the model, and how the model calculates hydraulic behavior in a system.

Frictional Losses

Each non-Newtonian fluid model adjusts the frictional losses in the system from the Newtonian fluid model. The equations and correlations used to determine pipe frictional losses are detailed on each model’s page. These methods to determine frictional losses replace the pipe friction model specified in the Pipe Properties window. For pipe Fittings and junction-specific losses, all non-Newtonian models use the same method, as detailed in the Laminar and Non-Newtonian Corrections panel topic.