Absolute measurement of laminar shear rate using photon correlation spectroscopy.

Measurement of the components of the shear rate tensor S in a fluid provides insight into the properties of that fluid. We detail a refined method for performing direct and absolute measurement of the components of S in a fluid using photon correlation spectroscopy, which we show gives an absolute, accurate, noninvasive measurement of the shear rate from a single measurement at a single location. We demonstrate this method in a cone and plate rheometer, where we obtain measurements of the shear rate of water in 10 s with an absolute accuracy of 2%.