Authors:

Matthew S Leight

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About Paper:

One complex threat faced by hypersonic vehicle designers is found in microscopic-sized ice and liquid particles that make up clouds in the upper atmosphere. These particles can fragment across shock waves emanating from hypersonic vehicles and cause damage by impacting and cratering the vehicle surface; yet, literature contains few experimental observations of their breakup phenomena. This study uses Purdue's 3-Inch Shock Tube to classify the breakup modes of such particles across shock waves from Mach 1 to 3, predict the size and shape of child particles, and propose physical models for breakup. The initial phase of the project examines the effect of droplet surface tension and viscosity on breakup regime by varying droplet chemistry. Aqueous solutions of isopropyl alcohol are created, dispensed into the shock tube, and hit with a shock. The breakup is captured with a high-speed camera using a Schlieren optical system, while pressure traces are recorded by pressure transducers within the tube. High-speed video shows the development of vibrational, bag, bag-and-stamen, and stripping type breakup, along with various transitional breakup modes. Analysis of droplet and shock properties reveals breakup regimes distinguished through Weber and Reynolds numbers. Timing delays of the electrical burst system are collected for use of particle-shock synchronization later in the study. Results show Weber and Reynolds numbers can be used as predictive tools for modelling particle breakup in supersonic flight regimes. However, overlap in breakup regimes and the existence of transitional modes may necessitate use of probabilistic models for particle size in damage assessment. Keywords: Shock Tube; Droplet Breakup; Schlieren Videography; Atmospheric Particles

Source:

Purdue University / 2025

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Co-authors:

Matthew S Leight