How Fluids Behave Can Inform Grand Challenges

Like the 26.2-mile races he runs with his wife, Jesse Ault knows that being a mechanical engineer is a marathon not a sprint. That sentiment is essential to solving what he refers to as Grand Challenges, which build on the knowledge and ideas of scientists over time to impact the world for the better.  


“Engineering is a means through which ideas can become a practical reality and revolutionize the world,” says Jesse, a graduate student in the Department of Mechanical and Aerospace Engineering at Princeton University. “I am particularly interested in the identified Grand Challenges that address some of the most pressing needs in the world, such as developing better medicines, providing clean water, and securing cyberspace.”


So it should come as little surprise that Jesse’s career led him to study fluid mechanics, a branch of physics that has tremendous application in these areas. His laboratory explores the properties of fluids in different states, including liquid, plasma, and gas, along with the forces that act upon them. Jesse’s work, more specifically, tries to understand how these fluids behave in complex, curving geometric systems, like nuclear power plants, chemical reactors, natural ecosystems, and even the human body.


“Understanding how flows behave in complex geometries can have a critical impact on safety and efficiency, as well as provide inspiration for new applications and technologies,” Jesse explains. “Being able to describe these fluid motions has potential applications across a range of industries,from chemical processing, natural gas, and energy sectors to biological flows and drug delivery.”


Raised on a farm in rural Indiana, Jesse completed his undergraduate degree in Mechanical Engineering at Purdue University with minors in Math and Physics. Some of his undergraduate research involved self-propelled nanomotors, Microelectromechanical Systems (MEMS), and characterizing a new type of rocket fuel. Now at Princeton, part of Jesse's research involves studying the flow in curved geometries and branching junctions. The branching flow is interesting, because it was recently found that under certain conditions, particles can accumulate and become permanently trapped in the flow through a phenomenon called vortex breakdown.


“This unexpected result could have important consequences, for example, in plants that process explosive gases,” explains Jesse. “As part of my research, I demonstrate how we can design systems that avoid dangerous gas and particle buildup.”


Understanding these curving, three-dimensional flows also has potential use for biological applications. These ideas have the ability to predict how particles can be captured, sorted, or focused in flow networks, and could thus be used to inform and design new drug delivery systems. This work could also potentially be used to estimate forces and stresses on blood vessels or arteries in the human body, possibly improving our understanding of conditions such as aneurysms.


To understand how these flows behave, Jesse uses a three-pronged approach, including theoretical considerations, experiments, and numerical simulations. His advisor, Howard Stone, PhD, the Donald R. Dixon ’69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering, says it is unusual that a student has the skill set and interest to perform all of these research applications well.  


“Jesse’s work is important because, rather surprisingly, understanding and documenting flows in common pipe geometries, has not been studied carefully for a wide range of conditions,” says Professor Stone. “He is a disciplined researcher and is able to ask and answer just the right question in order to rapidly move a research problem forward.”


That ability to solve problems recently led Jesse to receive the Mary and Randall Hack Graduate Award from the Princeton Environmental Institute. This award provides funding for another one of Jesse's projects that focuses on improving the efficiency of solar stills and evaporative coolers—technologies that are used to purify water and provide refrigeration in third-world nations. By using a superhydrophilic aluminum wire mesh, Jesse’s team can provide a large surface area for evaporation, which increases the efficiency of these devices.


When he is not in the laboratory, Jesse also likes to study issues related to privacy and security, along with topics ranging from Austrian economics and libertarianism to Rubik's cubing and the philosophy of teaching. He also enjoys power lifting and running when he has the time. After he graduates, Jesse plans to pursue a faculty position in computational fluid dynamics, and will possibly be heading back to work at Purdue University someday.


-Carolyn Sayre