Abstract
A newly designed eccentric cylinder device has been used to study the deformation and orientation of single Newtonian droplets immersed in an immiscible Newtonian liquid in a controlled complex flow field. Optical microscopy coupled with image acquisition analysis allows monitoring the dynamics of droplets flowing in the gap between the eccentric cylinders. Throughout the experiments, the flow intensity was kept below the critical conditions for droplet break-up. The experimental results are compared with predictions which are obtained using the transient form of the phenomenological model of Maffettone and Minale (J Non-Newtonian Fluid Mech 78:227–241, 1998; J Non-Newtonian Fluid Mech 84:105–106, 1999), incorporating a flow type parameter that accounts for the relative amount of elongational effects in the flow field and adapting the capillary number to mixed flows. For all the sub-critical flows studied here, good agreement was found between model predictions and experimental data, providing, for the first time, a quantitative assessment of drop shape predictions in complex flows.
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Acknowledgements
The authors would like to thank Ing. Bart Caerts for his valuable input during the design of the new ECD as well as Dr. Maarten Vanierschot and Dr. Tim Persoons of the Mechanical Engineering Department of the KULeuven for their help with the PIV measurements. This work has been financially supported by Onderzoeksfonds K.U.Leuven (GOA 03/06 and GOA 09/002).
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Boonen, E., Van Puyvelde, P. & Moldenaers, P. Droplet dynamics in sub-critical complex flows. Rheol Acta 48, 359–371 (2009). https://doi.org/10.1007/s00397-008-0322-z
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DOI: https://doi.org/10.1007/s00397-008-0322-z