Aerospace Mechanics Research Center (AMReC)

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 Boulder researchers huddle around two wind tunnels—long metal tubes that blow air currents at controlled speeds.

Laura Shannon, a graduate student in CU’s Paul M. Rady Department of Mechanical Engineering, turns a dial, releasing a hiss of gas that quickly ignites a burner inside one tunnel.

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.”

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Nuclear-powered missiles—How they work, what Russia's claimed test means for global strategic stability

Jeff Zehnder — Fri, 31 Oct 2025 21:59:22 +0000

Nuclear-powered missiles—How they work, what Russia's claimed test means for global strategic stability Jeff Zehnder Fri, 10/31/2025 - 15:59

The Russian military claims to have flown its Burevestnik nuclear-powered cruise missile 8,700 miles over 15 hours. Read from CU expert Iain Boyd on The Conversation.

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Construction secrets of honeybees: Study reveals how bees build hives in tricky spots

Jeff Zehnder — Thu, 11 Sep 2025 19:10:59 +0000

Construction secrets of honeybees: Study reveals how bees build hives in tricky spots Jeff Zehnder Thu, 09/11/2025 - 13:10

On a hot summer day in Colorado, European honeybees buzz around a cluster of hives near Boulder Creek. Worker bees taking off in search of water, nectar and pollen mingle with bees that have just returned from the field. Inside the hives, walls of hexagons are beginning to take shape as the bees build their nests.

“Building a hive is a beautiful example of honeybees solving a problem collectively,” said Orit Peleg, associate professor in CU Boulder’s Department of Computer Science. “Each bee has a little bit of wax, and each bee knows where to deposit it, but we know very little about how they make these decisions.”

In an August 2025 study in PLOS Biology, Peleg’s research group collaborated with Francisco López Jiménez, associate professor in CU’s Ann and H.J. Smead Department of Aerospace Engineering Sciences, and his group to offer new insight into how bees work their hive-making magic—even in the most challenging of building sites.

The new findings could spark ideas for new bio-inspired structures or even new ways to approach 3D printing.

How and why bees build honeycomb

Honeybees can build nests in any number of places, whether it’s a manmade box, a hole in a tree trunk or an empty space inside someone’s attic. When a bee colony finds somewhere new to call home, the bees build their hive out of honeycomb—a waxy structure filled with hexagonal cells—on whatever surfaces are around.

Building a beehive is hard work, and it consumes a lot of resources. It all starts with honey, the nutrient-dense superfood that helps bee colonies survive the winter.

To make honey, bees spend the warmest months gathering nectar from flowers. The nectar mixes with enzymes in the bees’ saliva, and the bees store it in honeycomb cells until it dries and thickens.

It takes roughly 2 million visits to flowers for bees to gather enough nectar to make a pound of honey. Then, each worker bee must eat about 8 ounces of honey to produce a single ounce of the wax they need to build more honeycomb.

If the surface of their building site is irregular, the bees have to expend even more resources building it, and the resulting comb can be harder to use. So efficiency is key.

In an ideal world, bees try to build honeycomb with nearly perfect hexagonal cells that they use for storing food and raising young larvae into adults. Mathematically, the hexagonal shape is ideal for using as little wax as possible to create as much storage space as possible in each cell.

The honeycomb cells are usually a consistent size, but when bees are forced to build comb on odd surfaces, they start making irregular cells that take more wax to build and aren’t as optimal for storage or brood rearing.

Irregular surfaces: A puzzle for bees to solve

This hive frame shows a foundation with a smaller cell size than what bees would typically build. The bees adjusted their building strategies to adapt. (Credit: Patrick Campbell)

Golnar Gharooni Fard, the lead author of the new study and a former CU graduate student, said her main goal in the study was to understand how bees work together to solve the structural problems they might run into.

“We wanted to find the rules of decision-making in a distributed colony,” Fard said.

The researchers 3D printed panels, or foundations, for bees to build comb on. The team imprinted the foundations with shallow hexagonal patterns with differing cell sizes—some larger, some smaller, and some closer to an average cell size—and added the foundations to hives for the bees to use.

Next, the researchers used X-ray microscopy to analyze patterns in the comb the bees built on each type of foundation. Depending on which foundation they were given, the bees used strategies like merging cells together, tilting the cells at an angle or layering them on top of one another to build usable honeycomb.

Giving bees these different surfaces to work with was like giving them puzzles they had to solve, said López Jiménez.

“All those things happen in nature. If they're building honeycomb on a tree, and at some point they get to the end of the branch, the branch might not be super flat, and they need to figure that out,” he said.

It’s still not clear why bees use the strategies they use in all situations. That’s a question the researchers hope to continue exploring.

Meanwhile, the team sees numerous possible applications for their findings. For example, honeycomb could inspire designs for efficient, lightweight structures such as those used in aerospace engineering.

López Jiménez also likened the honeycomb building process to 3D printing, where each bee gradually adds tiny bits of wax to the larger structure.

“The bees take turns, and they organize themselves, and we don't know how that happens,” he said. “Can we learn from how the bees organize labor or how they distribute themselves?”

CU graduate student Chethan Kavaraganahalli Prasanna was also part of the research

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$750,000 grant to advance naval aviation materials research

Jeff Zehnder — Tue, 02 Sep 2025 15:30:41 +0000

$750,000 grant to advance naval aviation materials research Jeff Zehnder Tue, 09/02/2025 - 09:30

Jeff Zehnder

Maryam Shakiba is studying complex composite materials with machine learning to make stronger and lighter aircraft for the Navy.

Shakiba, an assistant professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences, is leading a $750,000 grant from the Office of Naval Research, Aerospace Structures and Materials, to use machine learning techniques to advance composites made with additive manufacturing – more commonly known as 3D printing.

“Additive manufacturing has advanced a lot in the last few years,” Shakiba said. “We can now print complex, fiber-reinforced composite materials. Because we can print more complex patterns, we also need fast computational approaches that can model and predict the response of those materials.”

Navy aircraft technology has generally used metal body panels, but are starting to rely more on composite materials, like passenger jets have for years. Modeling the performance of such materials prior to construction is critical to determining their strength and potential failure points.

Traditionally, this requires finite elements analysis, a tried-and-true method of mathematical modeling. However, the complexity of the method demands major computing resources.

“If you have a material and you change one parameter, a finite elements simulation takes a few days. We need faster models to explore the design space better,” she said.

Shakiba’s work in machine learning is opening new opportunities for that modeling.

“We’ve integrated a convolutional neural network and a graph neural network that increases accuracy and decreases the amount of data you need to put in to get good results. The preliminary results show you can reduce the training data by at least 50 percent,” Shakiba said.

Even with a need for dramatically less data, the work requires supercomputers, like CU Boulder’s Blanca cluster, but the results are spit out in seconds instead of days.

Over the course of the three-year grant, Shakiba and her team, which includes partners at Johns Hopkins �Թ��, will advance these machine learning tools with increasingly complex composite patterns. The goal is to combine analysis of materials at both micro- and macro-scale to develop a complete picture of a composite’s response to stress.

“There is a huge interest from the federal government in decreasing the amount of time it takes to design to using a material it in the field,” Shakiba said. “Our method can do that.”

Maryam Shakiba is studying complex composite materials with machine learning to make stronger and lighter aircraft for the Navy. Shakiba is leading a $750,000 grant from the Office of Naval Research, using machine learning techniques to...

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Supercomputer fluid dynamics research highlighted by Interesting Engineering

Jeff Zehnder — Mon, 04 Aug 2025 18:45:20 +0000

Supercomputer fluid dynamics research highlighted by Interesting Engineering Jeff Zehnder Mon, 08/04/2025 - 12:45

Ken Jansen's research analyzing airflow around commercial aircraft to inform the design of next-generation planes is spotlighted in a new article from Interesting Engineering.

The work is utilizing an exascale system operated by the U.S. Department of Energy's Argonne National Laboratory.

Jansen, a professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences, is an expert in computational mechanics and fluid dynamics.

“These simulations help improve the predictive models that are applied to even more complex cases, such as capturing the flow physics around a full vertical tail and rudder assembly of an aircraft at full flight scale,” he said.

Read the full article at Interesting Engineering...

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New quantum physics and AI-powered microchip design software awarded grants

Jeff Zehnder — Thu, 24 Jul 2025 19:21:12 +0000

New quantum physics and AI-powered microchip design software awarded grants Jeff Zehnder Thu, 07/24/2025 - 13:21

Semiconductors—substances that can selectively conduct or block electricity—have been dubbed the “brains of modern electronics.” They form the building blocks of the chips that power electronic devices from laptops to smartphones and tablets to sports watches.

But semiconductors generate heat when they’re working, and they can easily get too hot, which hurts their performance and can damage them. While smaller chips are denser and more efficient at processing, they are harder to keep cool because of their size.

Sanghamitra Neogi, an associate professor in the Ann and H.J. Smead Aerospace Engineering Sciences department, is exploring ways to protect semiconductors and microchips from heat damage. She specializes in nanoscale semiconductors, which are so tiny their parts are measured in nanometers (billionths of a meter).

Sanghamitra Neogi speaks about her startup, AtomTCAD Inc., at CU Boulder's Ascent Deep Tech Community Showcase on June 25, 2025. (Credit: Casey Cass/CU Boulder)

Neogi and her research group, CUANTAM Laboratory, have developed a sophisticated software called AtomThermCAD that can predict how the materials in a microchip generate and respond to heat, which determines whether the chip will ultimately fail from overheating. AtomThermCAD is short for Atom-to-Device Thermal Computer Aided Design software for nanometer-scale semiconductor devices. The research behind this software was primarily supported by a $1 million DARPA MTO Thermonat grant awarded between 2023 and 2025.

Earlier this year, Neogi launched a startup to bring the software to market for semiconductor manufacturers and other customers. To kickstart her new company, AtomTCAD Inc., Neogi received $150,000 in recent grant funding from the state’s Office of Economic Development and International Trade, or OEDIT, matched by another $50,000 from Venture Partners at CU Boulder, which helps CU faculty and researchers turn their discoveries into startups and partnerships through funding and entrepreneurial support.

The grant from OEDIT was an advanced industries proof-of-concept grant for researchers in advanced industries. Managed by OEDIT’s Global Business Development division, this funding is intended to accelerate innovation, promote public-private partnerships and encourage commercialization of products and services to strengthen Colorado’s economy.

OEDIT Executive Director Eve Lieberman said that Neogi’s work will benefit the entire semiconductor industry, a rapidly growing segment of Colorado’s economy.

“Dr. Neogi’s research addresses one of the industry’s toughest challenges by improving heat management at the nanoscale, which boosts chip performance and supports the growth of Colorado’s advanced technology sector,” Lieberman said.

Chip designers use software like Neogi’s to test their designs without needing to actually build the chips. But unlike most chip design software, AtomThermCAD uses AI-accelerated quantum physics calculations to model the semiconductors and their components at an atomic level so it can accurately predict whether semiconductors or transistors too small to be seen by the naked eye will overheat.

The software could accelerate technological advancement by saving chip designers months, if not years, of time they previously had to spend developing and testing their designs.

Neogi drew on her expertise in physics and quantum technology to develop the software. She said as microchip components get smaller and smaller, approaching the level of individual atoms, researchers need to look to quantum physics to understand how the components behave.

Neogi also feels her approach could have applications beyond microchip development.

“What we developed is a method where you can model the thermal phenomena of any kind of nanoscale tech device,” she said. “Beyond microchips, it could be nanoscale medical devices and implants inside your body, or even drug delivery systems.”

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CU Boulder establishes Colorado Space Policy Center

Jeff Zehnder — Tue, 24 Jun 2025 20:34:37 +0000

CU Boulder establishes Colorado Space Policy Center Jeff Zehnder Tue, 06/24/2025 - 14:34

The �Թ�� of Colorado Boulder has established the Colorado Space Policy Center—positioning itself as a new resource on the forefront of an evolving landscape in national and global space exploration.

The center is designed for original research; discussion and debate on space policy issues; and educational programming. The work of the center will address advances in space science and technology, the role of government, the growth of commercial space, increases in global entrants and civilian-military interactions within the space sphere.

The center will seek to tie together entities within the university that involve space science, engineering, exploration, law and business in the aerospace context.

CU Boulder’s Research & Innovation Office, Office of the Provost, College of Arts and Sciences, College of Engineering and Applied Science and Leeds School of Business represent key partners in the launch of the CSPC.

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Golden Dome: Aerospace engineer explains proposed nationwide missile defense system

Jeff Zehnder — Fri, 23 May 2025 17:10:39 +0000

Golden Dome: Aerospace engineer explains proposed nationwide missile defense system Jeff Zehnder Fri, 05/23/2025 - 11:10

Professor Iain Boyd has a new column in The Conversation about the Golden Dome missile defense proposal.

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Aircrafts of the future: Boosting aerodynamic performance by engineered surface vibrations

Jeff Zehnder — Mon, 24 Mar 2025 15:04:27 +0000

Aircrafts of the future: Boosting aerodynamic performance by engineered surface vibrations Jeff Zehnder Mon, 03/24/2025 - 09:04

Jeff Zehnder

“This is probably the most radical conceptual advancement for airplanes since the replacement of propellers with jets.” – M.I. Hussein

Mahmoud I. Hussein is not pulling punches about the potential impact of a major aerospace materials research project.

As the principal investigator of a $7.5 million, five-year Department of Defense Office of Naval Research (ONR) Multidisciplinary �Թ�� Research Initiative (MURI), Hussein is leading an effort to reshape the fundamental character of fluid-structure interactions to reduce drag on high-speed aerospace vehicles—the focus of the project.

“Since the dawn of aviation, aircraft design has been based on the premise of shaping the surface of the vehicle to create lift and minimize drag. Our team is pursuing a new paradigm where the phononic properties, or intrinsic vibrations, of a surface or subsurface provide an additional pathway to interact with the airflow, to enhance the vehicle performance in an unprecedented manner,” said Hussein, the Alvah and Harriet Hovlid Professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences at the �Թ�� of Colorado Boulder.

Hussein also has a courtesy appointment in the Department of Physics and an affiliation with the Materials Science and Engineering Program.

MURI Partners

�Թ�� of Colorado Boulder

Mahmoud I. Hussein
Professor & Principal Investigator
Armin Kianfar
Post-Doctoral Associate
Adam Harris
PhD Student

�Թ�� of Maryland

Christoph Brehm
Associate Professor

Johns Hopkins �Թ��

Kevin Hemker
Professor

Purdue �Թ��

Joseph Jewell
Associate Professor

Applied Physics Laboratory

Keith Caruso
Principal Staff Engineer
Ken Kane
Researcher

�Թ�� of Kentucky

Alexandre Martin
Professor

Case Western Reserve �Թ��

Bryan Schmidt
Assistant Professor

Office of Naval Research (Program Directors)

Eric Marineau
Eric Wuchina

Phononic Subsurfaces

Turbulent airflow is detrimental to the fuel economy and the surface temperature of aircrafts as they soar through the atmosphere. This research aims to mitigate the transition to turbulence using phononic subsurfaces (PSubs) – synthetic designed materials affixed beneath the surface of a wing or vehicle body that passively manipulate small-amplitude vibrations, and by extension flow fluctuations, point-by-point along the surface.

Turbulence and Fuel Economy

Passenger planes consume over 10,000 gallons of jet fuel on a single cross-country trip, so improvements in fuel economy could lead to big savings for airlines. The potential in hypersonic crafts is even more dramatic.

Hypersonic vehicles travel at velocities at least five times the speed of sound. The turbulence that results from such speeds causes the surface of the vehicles to heat up to thousands of degrees, requiring they be constructed of exotic, expensive materials.

“By introducing a phononic subsurface to precisely shape the vibrations along the surface, we can alter the way the air interacts with the vehicle such that we ultimately don’t need to come up with exceedingly high-temperature-resistant materials,” Hussein said. “We’re passively manipulating instabilities in air flow in a manner that is favorable in the boundary layer where the vehicle meets the surrounding air.”

2015 to Today

The concept of PSubs was discovered by Hussein. The work began from a collaboration over 15 years ago between Hussein and then CU Boulder Professor Sedat Biringen, who died in 2020. As leaders in the newly-born research area of phononics and the longstanding field of fluid dynamics, respectively, they worked together to theoretically demonstrate–for the first time–a way to manipulate phonons to improve the efficiency of flight, with tremendous potential for the aerospace industry and prospects for application to water vessels as well.

Recently Hussein gathered a team of experts from across the country to take the concept of PSubs to the next level with this hypersonics MURI grant. Over the duration of the project, the group will develop high-fidelity models and fabricate functional prototypes to effectively characterize and demonstrate the technology in high-speed wind tunnels.

“We’re most confident about this endeavor, because the idea is rooted in fundamental science marrying–in quite a sophisticated fashion–fluid dynamics with condensed matter physics as well as with the emerging field of elastic metamaterials,” Hussein said.

“This is probably the most radical conceptual advancement for airplanes since the replacement of propellers with jets.” – Mahmoud Hussein is not pulling punches about the potential impact of a major aerospace materials research project.

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Advancing real-time data compression for supercomputer research

Jeff Zehnder — Thu, 13 Mar 2025 16:36:02 +0000

Advancing real-time data compression for supercomputer research Jeff Zehnder Thu, 03/13/2025 - 10:36

Jeff Zehnder

(Clockwise from top left) Alireza Doostan,
Ken Jansen, Stephen Becker, and John Evans.

Alireza Doostan is leading a major effort for real-time data compression for supercomputer research.

A professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences at the �Թ�� of Colorado Boulder, Doostan is the principal investigator on a $1.2 million Department of Energy project to change how researchers handle the massive amounts of data that result from complex physics problems like modeling turbulence and aerodynamics for air and space craft.

Compressing data is nothing new when it comes to computing, but advances in high- performance systems are now creating so much data that it becomes impossible to store for later analysis.

“Computing power has increased drastically, but moving and storing that data is becoming a bottleneck. We have to reduce the size of the data generated through large scale simulation codes,” Doostan said.

While some scientific analysis of turbulence flows can be completed faster on ever larger high-performance computing platforms, much of the information must be discarded because the scope of the data is too vast to store, making it impossible to conduct later assessments.

“There is a lot of structure and physics embedded in the data that ideally needs to be preserved to study complex flow physics or develop faster models,” Doostan said.

The goal of the grant is to both maintain accuracy of modeling data while decreasing its complexity, and critically, allowing it to be stored by compressing it in-situ, or in real-time as it is created during modeling. This is not currently possible for large-scale models, as existing technology often requires some or the entire modeling simulation be completed before compression can begin.

Joining Doostan on the project is a team of CU Boulder faculty, including Ken Jansen and John Evans, both also from Smead Aerospace, and Stephen Becker from applied math.

The team is focused on development of both traditional and deep neural models for massively parallel implementation of novel linear and non-linear dimensionality reduction techniques. It is a major undertaking, bringing together researchers with a broad range of backgrounds, including computational physics and sciences, discretization, machine learning, linear algebra, and statistics.

“This is a very interdisciplinary problem,” Doostan said. “This is not a problem one person can solve. You need a team.”

For Jansen, whose research focuses on turbulence modeling, an advance in compression could lead to significant progress across the spectrum of high-performance computing.

“This data compression research is critically important to provide access to the dynamics of our simulations,” Jansen said. “As simulations have passed petascale and are now exascale, it has become impractical to write the full solution fields to disk at a sufficient frequency and count, owing to the broad range of spatial and temporal scales of turbulence.”

The group has completed soon-to-be-published research showing strong promise for their approach. They are now working to scale up their algorithms to work at scale on supercomputing platforms like CU Boulder’s Blanca cluster as well as Department of Energy systems.

“There is still a lot to be done, but our early work has shown success and only increases the computational load by less than five percent,” Doostan said.

The three-year award runs through fall 2027. Doostan is hopeful their final product will include publicly available next-generation compression software for general use by all simulation practitioners.

Alireza Doostan is leading a major effort for real-time data compression for supercomputer research. Doostan is the principal investigator on a $1.2 million...

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