Investigation of the viscoelastic effect on the Metzner and Otto coefficient through LDA velocity measurements

The Metzner and Otto correlation is the single practical method for incorpo rating non-Newtonian effects in the mixing process. In this article, the Me tzner and Otto's idea, the role of viscoelasticity on the Metzner and Otto coefficient, k(s), effects of how regime on k(s) and the determination of k (s) for Rushton turbine impeller have been studied using the direct method of the laser Doppler anemometry (LDA) velocity measurement for the case of viscoelastic liquids. The normalised mean tangential velocity profiles are independent of Rushton turbine impeller speeds. Contrary to literature find ings, it is shown that the variation of local shear rate against the impell er speed is better correlated by the power equation, i.e. (gamma )over dot = k(s)'.N-b', in the transition region, i.e. similar to 30 < Re <similar to 2000. Also, a correlation between improved coefficient, Ic:, and the elast icity number of viscoelastic liquids is given which is very helpful in desi gning of the mixing of both viscoelastic and inelastic non-Newtonian fluids through relating rheological properties to kinematical and dynamical param eters of the mixing process.