Rabinowitsch Correction

The Rabinowitsch (or Weissenberg-Rabinowitsch) correction is applied to get more accurate shear rate values from non-Newtonian materials measured using a capillary flow technique.

The basic shear rate equation for capillary flow is based on Newtonian fluids, where the velocity profile from pressure-driven flow in a capillary is shown to be homogenous (parabolic); however, for non-Newtonian fluids such as the shear thinning behavior of polymer melts, the inhomogeneous flow contributes to what can sometimes be significantly higher shear rates at the boundary wall.

The correction takes into account the non-parabolic velocity flow where the shear rate at the wall is usually higher.

For fluids obeying the Power Law, the correction is simply, the

where γa is the apparent shear rate at the wall and n is the Power Law index.