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Exploring acetone excitation for nonintrusive laser diagnostics of high-speed flow may sound pretty abstract, but it’s actually a simple concept, insists David Shekhtman, PhD, assistant professor of mechanical engineering.

“Think about the steam coming up from a cup of coffee; that’s a flow tracer. That is, you can see the flow of the gas, so you know how fast it is moving. In our lab, I’m working with students to create a more accurate flow speed measurement.”

Traditional methods of measuring flow velocity include injecting particles (glass beads or smoke particles, for example) into a fluid to visualize and measure speed. But the particles don’t move with the flow as they should, so the scientific community has been moving away from this method, looking for one that is not hampered by the limitations of drag. Using the gas itself, said Dr. Shekhtman, allows researchers to measure far more accurate flow speed.

With the grant he was awarded from NASA in 2023, Dr. Shekhtman has been using a 266-nm laser to excite the molecules in acetone, an atomic process that causes fluorescence. The acetone is then injected into a fluid so that its movement, or flow, can be captured on a camera with timing equipment that has an accuracy of nanoseconds.

Dr. Shekhtman predicts that eventually, this method will be used to validate computational fluid models for turbulence. “NASA is specifically looking towards the commercialization of hypersonic technology,” he said. “This could potentially help with the design of hypersonic aircraft or antimissile hypersonic bullets.” NASA, he noted, is involved in aeronautics as well as space; objects to be tested include those that work at flight altitude.

A former student of Dr. Shekhtman’s, Tim Keenoy MS’24, explained further, “When you get up to really high speeds, pressure builds up and temperature rises, and you get extreme heat — the kind of heat that can melt an aircraft. But if you are able to create an accurate measurement, you can map the velocity, know where to worry about heat buildup, and can address it.” Inspired by their work together, Keenoy is currently pursuing a PhD with a focus on hypersonic technology at New Jersey’s Stevens Institute of Technology.

At ¾«¶«´«Ã½, mechanical engineering major Emily Alfonso Olmos ’27 is continuing the research with Dr. Shekhtman. She’s looking forward to the next step in the project: the building of a wind tunnel that can release gas at a rate of 1,000 to 2,000 meters per second.

The wind tunnel — consisting of a pressurized pipe, a nozzle that expands the flow, and a test section to receive the pressurized gas and conduct the flow diagnostics — is needed to generate the flow field. Dr. Shekhtman is currently working on the wind tunnel design, which he submitted to NASA with the hope of securing a grant to build it.

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