John Farnsworth

Wind tunnel research could help predict how wildfires spread

Jeff Zehnder — Fri, 05 Dec 2025 21:56:10 +0000

Wind tunnel research could help predict how wildfires spread Jeff Zehnder Fri, 12/05/2025 - 14:56

In a windowless, warehouse-sized lab on campus, a team of CU ��ý�� researchers huddle around two wind tunnels—long metal tubes that blow air currents at controlled speeds. The crew turns out the overhead lights. The fire, glowing blue and yellow through a window in the tube, is the only light to be found. Shannon turns on the air current, speeding it up and slowing it down, and the flames flicker and sway wildly.

The researchers are using the wind tunnels to study wildfire behavior. For nearly a decade, the team has been delving into the hundreds of factors that can affect the way wildfire starts, moves and spreads, as well as the damage it causes.

Ultimately, the team has an ambitious goal: to build computational tools that can predict how wildfire will behave. They envision a day when, shortly after a fire starts, firefighters can plug in details about it and learn where—and how quickly—it could spread. The tools could help keep communities safer in a world where climate-driven wildfire is becoming more common—and more dangerous.

“Being able to have more accurate, better predictors of fires is extremely important to protecting people, lives and property,” said Shannon. “The more accurate we can make our simulations in the long run, the safer we can keep wildfires.”

The research team also brings a unique, interdisciplinary approach to studying wildfire, blending ideas and technology from mechanical and aerospace engineering.

“This research was driven by recognizing that there was a gap. There were these really advanced aerodynamics and sensing tools that had not been used in this field yet,” said Greg Rieker, a research team member and professor in the Paul M. Rady Department of Mechanical Engineering.

Teasing apart the elements of wildfire

Wildfire behavior is complex and hard to predict because there are so many variables—like wind, rain, humidity, fuel and topography—to consider. The researchers have been methodically isolating and studying these variables to understand more about how fire behaves under different conditions.

The team is using wind tunnels to better understand basics like how fire moves, its shape and structure, and how it transfers heat downstream. They’re also looking at the impact of ground slope on fire spread, using a tunnel that can tilt at an angle.

“The idea is to model the influence of ground slope to think about wildfires climbing hills versus descending. You have different physics and different dynamics,” said John Farnsworth, a team member and associate professor in CU’s Ann and H.J. Smead Department of Aerospace Engineering Sciences.

The team is also exploring how embers form and spread. Wind can carry these burning pieces of wood or debris miles away from a fire, sparking additional blazes. Embers were likely a major driver of the December 2021 Marshall Fire and the October 2020 East Troublesome Fire, which spread from Grand Lake to Estes Park overnight due to blowing embers.

A large smoke plume from the 2020 East Troublesome Fire in Grand and Larimer counties. Wind helped push the fire across the Continental Divide from Grand Lake to Estes Park, prompting massive evacuations. (Source: BLM)

In a study that has not yet been published, former mechanical engineering graduate student Charlie Callahan set one-millimeter wooden discs on fire to create embers, then dropped them into a wind tunnel and took a high-speed thermal video of the embers moving through the tunnel.

“Larger firebrands can travel long distances and start a fire a mile away, which causes fire spread. But also, small firebrands can change the rate of fire spreading over short distances,” Callahan said. “There hadn't been too many studies on looking at this specific size of firebrand.”

The study found that the embers, or firebrands, fluctuated rapidly in temperature—by hundreds of degrees—as they traveled through the tunnel. And the fluctuations happened more frequently in embers that were traveling at faster speeds compared to the wind speed. The faster they moved, the hotter they got.

Callahan and the other researchers plan to continue studying firebrands to understand more about the significance of these temperature changes and how they affect fire spread.

Looking forward

The researchers say it’s still extremely difficult for firefighters to predict how fires behave and spread, especially in areas with variable terrain and wind conditions. Fires such as the Marshall Fire and the East Troublesome Fire can spread more quickly and erratically than expected.

Scientists believe wildfire will likely become an even more significant threat as climate change progresses, temperatures rise and drought conditions persist in many areas. When fires happen, it’s crucial to be able to understand and predict how they’ll behave.

The work is particularly urgent for communities in the wildland-urban interface that border on wilderness and are more vulnerable to wildfire. The researchers hope their predictive tools might help improve evacuation plans and enhance firefighting approaches.

Peter Hamlington, a professor in the Paul M. Rady Department of Mechanical Engineering and the principal investigator behind this research, noted the impacts of wildfire extend beyond direct burn damage, and smoke from the fires can also travel long distances and negatively affect human health.

“A better understanding of the causes and dynamics of wildland fires will help us develop new computational tools for predicting the occurrence of fires and mitigating their most devastating effects,” Hamlington said.

“Ultimately, our project is focused on the development of more accurate and reliable predictive tools that can be used by those seeking to understand and reduce fire risk.”

Off

Traditional

White

Seminar: Experimental Investigations within Unsteady Aerodynamics and Flow Control - Sept. 15

Anonymous — Fri, 09 Sep 2022 19:40:55 +0000

Seminar: Experimental Investigations within Unsteady Aerodynamics and Flow Control - Sept. 15 Anonymous (not verified) Fri, 09/09/2022 - 13:40

John Farnsworth
Assistant Professor, Smead Aerospace
Thursday, Sept. 15 | 3:00 P.M. | AERO 111

Abstract: The safe flight of small unmanned aircraft or drones in gusty environments, the use of aeroelastically sensitive aircraft for communications and remote networking, and the efficient generation of renewable energy from wind turbines operating around obstacles and terrain are all directly limited by our understanding and control of unsteady, three-dimensional aerodynamic phenomena. My research group, the Experimental Aerodynamics Laboratory (xAero Lab), focuses generally in the areas of unsteady aerodynamics and flow control applied to aerospace vehicles and wind energy systems, however we have more recently applied our expertise to study select environmental flow problems including the forced evaporation in soils and the flame dynamics in wildland fires. Our approach is to elucidate the physical dynamics of complex three-dimensional unsteady flows through well controlled experimental investigations with a broad selection of conventional and optical fluid dynamic measurement techniques and uniquely designed facilities and experimental apparatus. I will provide an overview of ongoing basic research efforts in the xAero Lab related to each of these application areas.

Biography: John Farnsworth is an Assistant Professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences at the ��ý�� (CU), where he leads the Experimental Aerodynamics Laboratory (xAero Lab). Prior to joining CU in 2014, he was a Postdoctoral Research Associate in the Department of Aeronautics at the United States Air Force Academy. He received his Ph.D. in Aeronautical Engineering from the Rensselaer Polytechnic Institute (RPI) in 2011, where he also received both his B.S. and M.S. in Aeronautical Engineering, respectively in 2006 and 2007. His research interests lie in the areas of unsteady aerodynamics, fluid-structure interactions, turbulence, and the application experimental measurement techniques in fluid dynamics.

Off

Traditional

White

Burning up: CU researchers use unique wind tunnel to study wildfires

Anonymous — Mon, 16 Sep 2019 16:55:46 +0000

Burning up: CU researchers use unique wind tunnel to study wildfires Anonymous (not verified) Mon, 09/16/2019 - 10:55

Researchers at CU ��ý�� are using computations and experiments in a new sloping wind tunnel to study how wildfires form and move across different landscapes; applying cutting edge research tools to understand an old problem that Colorado has become quite familiar with in recent years.

Associate Professor Peter Hamlington leads the project. His group develops computational tools which allow researchers to understand how fire reacts at a variety of scales. Associate Professor Greg Rieker's team, including PhD student Amanda Makowiecki, developed and built the “WindCline” – a wind tunnel that can tilt up and down. They did so in consultation with Aerospace Engineering Assistant Professor John Farnsworth. The tunnel allows researchers to study how various fuels react to different conditions and allows for the study of emissions in a controlled setting using laser sensors.

Rieker and Hamlington said wind tunnels are traditionally used in studies of airplanes and car aerodynamics, but this sloping wind tunnel designed for wildfire research is the only of its kind anywhere in the world. It enables the CU College of Engineering and Applied Science team to reliably reproduce natural wildfire conditions in a way that has not previously been possible.

“Wildfires contribute to property damage and environmental impacts from emissions to possible groundwater contamination,” said Hamlington, who is part of the Department of Mechanical Engineering. “The tools we are bringing to bear on this problem are new for any type of combustion research, so we are taking the latest and greatest from one field and applying it to another. We are unique in the field of combustion research, so we are unique in the field of wildfire research.”

Wildfires are increasingly a problem in western states. In 2018 alone, Colorado saw 1,328 fires accounting for 475,800 acres burned according to the Insurance Information Institute. Researchers are being asked to help understand these events from many perspectives.

The WindCline was originally constructed through a research award from the Department of Defense’s Strategic Environmental Research and Development Program to examine the environmental impacts of prescribed burns on DoD property. Hamlington said the $1.1 million project uses adaptive mesh simulations and frequency comb laser diagnostics to give detailed info about many aspects of the fire.

“Ultimately, the proposed research will bring together two cutting-edge technologies, simulations using adaptive mesh refinement and frequency-comb laser diagnostics, for the first time in wildland fire research,” he said.

The ability to tilt and manipulate the flame in a lab environment could also help with a variety of research questions relating to how topography affects the fires. Studying how the flames react going uphill is especially important. That’s because fire usually travels uphill much faster than down. On the incline, before the fire even arrives, soon-to-be scorched areas have already been warmed by heat waves off the fire.

Rieker, who is also in the Mechanical Engineering Department, said this is quickly becoming an important research area for the college.

“It is an important research area for our region as well,” he said. “We are now planning a new project in the WindCline involving five CU ��ý��-based investigators with others at Colorado State University, the Los Alamos National Laboratory and elsewhere.”

Off

Traditional

White