AFT Impulse allows users to model constant or varying fluid properties.

• Constant Fluid Properties – all fluid properties are the same for every pipe and are as specified in the Fluid panel. Note that non-newtonian viscosity models will still cause the viscosity to vary if the constant fluid properties option is selected.

• Variable Fluid Properties - the values for density and viscosity in the Fluid panel are the default fluid properties. You can then enter different fluid property values, if desired, for any pipe in the Pipe Properties window. This does not mean that fluid properties can vary on their own in the model - they are constant in each pipe and must still be directly specified by the user.