Secondary atomization of elastic non-Newtonian liquid drops

Sharon E Snyder, Purdue University

Abstract

Secondary breakup occurs when aerodynamic forces cause a drop to deform and fragment. This process has been studied for almost a century, but most of the focus has been on Newtonian liquids. This thesis investigates the secondary breakup of elastic non-Newtonian liquid drops by using high speed photography to determine breakup morphology and breakup times. The drop deformation process was simulated using an extended version of the Taylor analogy breakup (TAB) model. This work begins with a review of the secondary atomization of Newtonian drops. Breakup morphology, breakup times, and modeling efforts are reviewed and discussed. Focus in placed on experimental results which clarify the processes that lead to breakup. This is followed by a short discussion of the material available for non-Newtonian drops. Experimental and analytical model results are presented. Key findings include: 1.) Elastic non-Newtonian drop secondary breakup modes are qualitatively similar to those observed for Newtonian and inelastic non-Newtonian drops. In both non-Newtonian cases, the bag stretches more before it ruptures, and the resulting fragments persist longer than for Newtonian breakup. 2.) Two bag breakup times were defined: initial (Tini) and bag breakup (T bag) times. Tini increased with K. Three multimode breakup times are reported: initial ( Tini), the first bag breakup time (Tbag1 ), and the second bag breakup time (Tbag2). 3.) The TAB model was extended to elastic non-Newtonian liquids and was used to predict Tini for bag breakup, and also the cross-stream radius at that time.

Degree

M.S.M.E.

Advisors

Sojka, Purdue University.

Subject Area

Mechanical engineering

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