Research & Innovation

DoD Awards Grant to Develop Velocimetry of Hypersonic Flows

Nick Parziale, assistant professor in the Department of Mechanical Engineering, has received a $326,647 grant from the Defense University Research Instrumentation Program (DURIP) to purchase a state-of-the-art laser and camera system for the study of hypersonic flow physics.

The equipment will be essential to developing a new technique for characterizing the flow of gases at very high speeds, known as krypton tagging velocimetry (KTV). With this technique, researchers take snapshots of glowing krypton atoms as they move through a high-speed wind tunnel, allowing them to visualize the flow of air or other gases. This is akin to watching a dye drifting along flowing water.

In fact, a simple form of velocimetry was practiced in the 15th century by Leonardo da Vinci, an ardent observer of nature, who floated grass seeds on a stream and sketched their trajectories as they drifted along the water.

Today, researchers apply the same concept, seeding a flow with particles and observing their movement by various methods. For the study of high-speed gas flows, the current state of the art uses a variety of molecules as tracers, including oxygen, nitrogen, and nitric oxide. A laser pulse induces fluorescence in the tracer molecules, and a camera system captures the movement of the fluorescent tracer along a wind tunnel at microsecond or even nanosecond intervals.

However, a notable shortcoming of current tracers is their potential to react chemically with the surrounding air, thus distorting the measurement of the flow. Parziale’s research aims to solve this problem by developing a nonreactive tracer.

“The fundamental strength of KTV is that the tracer is inert,” explains Parziale. As a noble gas, krypton is practically immune to any chemical processes within the flow, making it an ideal tracer for aerodynamic research that may require a range of thermochemical environments. “Because of this flexibility, KTV can broaden the applications of tagging velocimetry in the study of hypersonic flow physics, particularly in non-equilibrium gas-phase flows,” says Parziale.

One application of interest to the Department of Defense (DoD) is studying the behavior of vehicles traveling at more than five times the speed of sound. This supports DoD efforts to improve rapid space access and conventional prompt global strike, that is, the ability to strike targets anywhere on Earth in as little as an hour.

The grant-funded laser system is comprised of a Nd:YAG Laser and supporting optics capable of generating the repeatable and narrowband 214.7 nm laser pulse needed for KTV purposes. The camera system is designed to image very low-level signals for very short exposure times.

The new laser and camera system will place Stevens at the forefront of KTV research and allow large-scale implementation of KTV through continuing collaboration with the Arnold Engineering Development Center (AEDC) in White Oak, Md. The results of this collaboration are outlined in an article published this June in Applied Optics.

“The equipment grant will also greatly increase the number of Stevens students exposed to fundamental research of interest to the Department of Defense,” adds Parziale.

Parziale conducted much of the proof-of-principle work on KTV during two Air Force Summer Faculty Fellowships at AEDC White Oak. This summer, Drew Zaradka (MS 2016) was also supported as a graduate research assistant by the fellowship program.

DURIP is sponsored by the DoD and supports the purchase of equipment that increases university capabilities for cutting-edge defense research and student training. The highly competitive program this year selected 225 awardees from nearly 700 proposals.