An experimental investigation of the breakup of a viscoelastic non-newtonian fluid in a supersonic stream

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Virginia Tech

A basic experimental study of the aerodynamic breakup of a viscoelastic non-Newtonian liquid injected into a supersonic stream was conducted. All test runs were made either at a free stream Mach number of 2.4 and a total pressure of 4.1 atm or a Mach number of 4.0 and a total pressure of 10.9 atm. The air flow had a total temperature of 300 K, and the injectant was always at room temperature. The injectant used for the majority of the test runs was diethylmalonate thickened with polymethyl-methacrylate, which has the characteristics of being viscoelastic. A limited number of test runs were made with glycerin in order to make a comparison between the behavior of Newtonian and viscoelastic non-Newtonian fluids. Several areas concerning the disintegration of the viscoelastic non-Newtonian fluid were investigated, including the effects of free stream Mach number, injection velocity, jet diameter, twin in-line jets, injection angle, and injector shape. Spark Shadowgraphs of 1.2 microsecond duration and high speed movies were obtained to qualitatively appraise the breakup behavior.

The breakup of the jet was found to be a function of free stream Mach number and jet diameter, injection angle, and frontal area. It also was observed that the breakup behavior of the viscoelastic non-Newtonian fluid is remarkably different from that of (Newtonian) glycerin. The time scales for breakup are substantially increased regarding the dissemination of the viscoelastic liquid as compared to the Newtonian glycerin. Furthermore, penetration of the viscoelastic non-Newtonian fluid was observed to be on the order of 50% less than that measured for glycerin at comparable injection conditions.