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Title:A pair of immiscible ternary liquids with matchable refractive indexes over a wide range of density and viscosity ratios
Author(s):Saksena, Rajat
Advisor(s):Christensen, Kenneth T.; Pearlstein, Arne J.
Contributor(s):Christensen, Kenneth T.; Pearlstein, Arne J.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Viscosity Ratio
Density Ratio
Refractive Index
Abstract:Use of particle image velocimetry, laser-induced fluorescence, and a number of other modern optical diagnostic techniques in two-phase flows is severely limited by the difference in refractive index across a fluid/fluid interface, which leads to optical distortion and significantly complicates data interpretation. This problem can be avoided if a surrogate pair of fluids is available, for which the index of refraction can be matched. Beyond that, dynamic similarity also requires that the density ratio of the two surrogate fluids, as well as their ratio of viscosities, match the corresponding ratios in the original fluid pair of interest. Here, we show how that matching can be accomplished, using two ternary liquids, for which adjustment of four independent composition variables (two for each phase if each component of each phase is insoluble in the opposite phase) allows matching of the refractive index over a range of density ratios and a wide range of viscosity ratios. The approach is illustrated for two pairs of fluids. In each case, one fluid is an oil phase consisting of a solution of a light silicone oil, a heavy silicone oil, and 1- bromooctane, which at room temperature are fully miscible over the entire range of compositions. Two opposite phases are considered: a “polar phase” consisting of N- methyl-2-pyrolidone, ethanol, and water, and an “aqueous phase” consisting of 1,2- propanediol, CsBr, and water. For the oil phase, the index, density, and viscosity were measured at 120 binary and ternary compositions. For the polar phase and aqueous phase, binary and ternary data were available in the literature, along with the saturation curve for the aqueous phase, in which the diol and water are fully miscible, but the solubility of the CsBr in water and the diol are both limited. (For the polar phase, the three components are fully miscible over the entire range of compositions at room temperature.) For each fluid phase, polynomials in the composition variables were least- squares fitted to the index and density, and to the logarithm of the kinematic viscosity. For both fluid pairs (polar and oil phases, and aqueous and oil phases), the range in overlap of index was determined, and the polynomial fits were used to determine the range of accessible density ratios that could be achieved for each index in the range of overlap. Both pairs of liquids are shown to provide compositions for which the density ratio and viscosity ratio of liquid CO2-water systems at high pressure can be matched, while simultaneously matching the index of the two surrogate fluids. While simple solubility tests indicate that one component of the oil phase (namely 1-bromooctane) has significant solubility in the polar phase, there is good reason to believe that fo0r the other fluid pair, no component of the oil phase is soluble in the aqueous phase, and no component of the aqueous phase is soluble in the polar phase. Finally, a second aqueous phase (1,2-propanediol, NaBr, and water) is identified that should have even better “matchability” characteristics than the 1,2-propanediol + CsBr + water phase, and will be attractive from economic and safety standpoints.
Issue Date:2013-12-13
Rights Information:Copyright 2013 Rajat Saksena
Date Available in IDEALS:2016-09-09
Date Deposited:2013-12

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