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Available online at www sciencedirect com International Journal of Multiphase Flow 34 2008 161 175 www elsevier com locate ijmul ow Atomization of viscous and non newtonian liquids by a coaxial high speed gas jet Experiments and droplet size modeling A Aliseda a 1 E J Hop nger a J C Lasheras a D M Kremer b A Berchielli b E K Connolly b a b Department of Mechanical and Aerospace Engineering University of California San Diego 9500 Gilman Drive La Jolla CA 92093 0411 United States Oral Products Center of Emphasis P zer Inc Global Research and Development Groton New London Laboratories Eastern Point Road MS 8156 07 Groton CT 06340 United States Received 15 May 2007 received in revised form 22 August 2007 Abstract This paper describes a collaborative theoretical and experimental research e ort to investigate both the atomization dynamics of non Newtonian liquids as well as the performance of coaxial atomizers utilized in pharmaceutical tablet coating In pharmaceutically relevant applications the coating solutions being atomized are typically complex non Newtonian uids which may contain polymers surfactants and large concentrations of insoluble solids in suspension The goal of this investigation was to improve the understanding of the physical mechanism that leads to atomization of viscous and nonNewtonian uids and to produce a validated theoretical model capable of making quantitative predictions of atomizer performance in pharmaceutical tablet coaters The Rayleigh Taylor model developed by Varga et al has been extended to viscous and non Newtonian uids starting with the general dispersion relation obtained by Joseph et al The theoretical model is validated using droplet diameter data collected with a Phase Doppler Particle Analyzer for six uids of increasing rheological complexity The primary output from the model is the Sauter Mean Diameter of the atomized droplet distribution which is shown to compare favorably with experimental data Critical model parameters and

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