��������

�� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� �� Elle Stark

It’s well known that animals rely on odors to survive. Bees, for example, can follow the scent of a flower from far away to collect nectar and pollen. But in turbulent air, how do bees and other animals trace those scents back to their source?

Understanding that relationship between wind and odor plumes is the focus of �������� PhD student Elle Stark’s work in the��Ecological Fluid Dynamics Lab.

Stark, who is part of a large NSF-funded scientific effort called the�� Network, was recently awarded a prestigious Gallery of Fluid Motion (GFM) Award for�� describing her research. The competition, part of the American Physical Society Division of Fluid Dynamics conference, was held in Houston on Nov. 23-25.

“The award reflects the quality of our research within the fluid dynamics community and the importance of using data visualization to communicate complex ideas," Stark said. “It’s a chance to share our findings in a way that connects with a broad audience.”

The video illustrates the lab’s years of research measuring precise data about odor plumes, which animals regularly use to locate food, mates and habitat.��

“Navigating natural plumes is a critical skill for many animals, yet we don’t fully understand how they do it,” Stark said. “The gaps in current knowledge stem partly from the complexity of how odors travel from a source to an animal.”

Hidden patterns

Odor2Action is an international network of scientists across 16 research institutions that seek to understand how animals use odors to guide natural behaviors.

This effort will help researchers better understand the sensory and behavioral processes in the brain, with broad implications for health and security for both animals and human beings. The work could inform search and rescue, chemical leak detection and even improvements in neural network architectures, computer models inspired by the brain.

��

Experimental setup for plume illumination. Precisely aligned lasers (center right), are sent through specialized sheet-forming optics (center left) to illuminate a slice of the plume in the wind tunnel (left).����

The Ecological Fluid Dynamics Lab studies how fluid dynamic processes shape the signal an animal encounters as it navigates an odor plume. For the work shown in the video, the researchers investigated odors moving through air, which required multiple lasers and cameras precisely timed to collect data across a 30 x 30 cm area.��

To measure flow, the researchers used particle image velocimetry, which tracks particles in the air and calculates their velocity from successive images. To measure odor, they released acetone vapor into the flow through a small tube that serves as the odor source. When a UV laser is shined on the acetone, it fluoresces in visible light, allowing them to photograph the evolving odor plume.��

Because the researchers measure both flow and odor simultaneously, they can better understand how the two are related, Stark said. The visual layers shown in the video reveal structures and boundaries within the flow, highlighting how closely flow and odor are linked. This relationship has been experimentally investigated in water plumes, but obtaining accurate and detailed time-resolved measurements in air has only recently been possible.��

Stark hopes that those watching the video come to appreciate the complexity and beauty of the fluid dynamics underlying “something as seemingly humble as an odor plume.”��

“Viewers can see structures in the flow shaping the odor, stretching and rotating it along the same regions where the flow itself is stretching and rotating,” Stark said. “At the same time, the odor diffuses outward, making it difficult to predict exactly how it will be shaped by these flow structures. These factors determine the odor cues an animal experiences."

Odor concentration (blue/purple) overlaid on flow patterns (gold lines), showing how odor moves with air.

“While computer simulations are powerful tools, taking direct measurements of physical phenomena is critical for discovering and testing theoretical dynamics in the real world,” Stark continued. “More broadly, we hope the viewer will understand that the fundamental physics of plume dispersion not only provides abstract scientific understanding but also drives the ecological and atmospheric processes that shape our world.”��

Looking ahead

The researchers are developing advanced analysis techniques to investigate the relationship between the flow and the odor under different plume conditions.��

“By rigorously quantifying these fundamental relationships, we hope to provide tools both for understanding olfactory navigation and, more broadly, understanding the fluid dynamics of flow and transport in these types of conditions.”