Experiments in Fluids

, 59:66 | Cite as

A novel method to create high density stratification with matching refractive index for optical flow investigations

  • Benedikt Krohn
  • Annalisa Manera
  • Victor Petrov
Research Article


Turbulent mixing in stratified environments represents a challenging task in experimental turbulence research, especially when large density gradients are desired. When optical measurement techniques like particle image velocimetry (PIV) are applied to stratified liquids, it is common practice to combine two aqueous solutions with different density but equal refractive index, to suppress particle image deflections. While refractive image matching (RIM) has been developed in the late 1970s, the achieved limit of 4% density ratio was not rivalled up to day. In the present work, we report a methodology, based on the behavior of excess properties and their change in a multicomponent system while mixing, that allows RIM for solutions with higher density differences. The methodology is then successfully demonstrated using a ternary combination of water, isopropanol and glycerol, for which RIM in presence of a density ratio of 8.6% has been achieved. Qualitative PIV results of a turbulent buoyant jet with 8.6% density ratio are shown.



We are indebted to colleagues at the Experimental and Computational Multiphase Flow Group of University of Michigan for many helpful discussions as well as assistance with various aspects of the experiments. The work was made possible by the generous support of DOE NEUP under Grant no 14-6552.


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© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Nuclear Engineering and Radiological SciencesUniversity of Michigan-Ann ArborAnn ArborUSA

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