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Aerospace engineering associate professor Vrishank Raghav let his curiosity run free while watching a pregame flight at Jordan-Hare Stadium. Now, he\u2019s studying the flight patterns of birds to learn how they fly seamlessly despite changing weather patterns.<\/strong><\/p><\/blockquote>\n
Vrishank Raghav<\/a> was enjoying his first experience at Jordan-Hare Stadium on a fall afternoon in 2018 when Nova \u2014 also known as War Eagle VII \u2014 took his traditional pregame flight to the delight of more than 80,000 fans. \u00a0 \u00a0<\/span><\/p>\n
Raghav, who had just joined the Department of Aerospace Engineering as an assistant professor, was intrigued by Nova\u2019s performance and how controlled it seemed while soaring through the air. After the game, he researched where Nova spent time when not rallying the Auburn Tigers to victory and learned of the Auburn University Raptor Center. \u00a0 \u00a0<\/span><\/p>\n
The Auburn University Raptor Center, a division of the College of Veterinary Medicine, is a rehabilitation and education facility providing critical education and conservation efforts for raptors.\u00a0 \u00a0<\/span><\/p>\n
Raghav and the Raptor Center soon formed a partnership. In 2018, he received funds from Auburn University\u2019s Intramural Grants Program (IGP) to study a red-tailed hawk named Petey. The goal was to learn how birds can quickly adapt to adverse aerodynamic environments due to changing weather conditions \u2014 where traditional aircraft and unmanned aerial vehicles seem to struggle. \u00a0 \u00a0<\/span><\/p>\n
\u201cYou look around on a bad weather day, and most flights are grounded, and there are delays all around the country,\u201d Raghav said. \u201cBut birds are still flying, and it appears that the bad weather doesn\u2019t affect them. The big question for us researchers and engineers is how they have adapted to achieve smooth flight in adverse conditions.\u201d \u00a0 \u00a0<\/span><\/p>\n
Wade Stevens, director of the Raptor Center, said studying nature\u2019s reactions to turbulence or wind gusts is an interesting concept that makes a lot of sense. \u00a0<\/span><\/p>\n
\u201cBirds are naturally adept at dealing with different factors they encounter in nature, especially when flying through harsh storms that ground most aircraft or cause delays,\u201d Stevens said. \u201cI think it\u2019s a natural progression to say, \u2018let\u2019s figure out how they do this,\u2019 and look for ways we can recreate all, or portions, of that.\u201d \u00a0<\/span><\/p>\n
Raghav and his team set up a row of upward-facing fans to generate wind gusts for Petey to fly through to track how he adjusts his flight pattern to compensate for the perturbation. However, before clearing Petey for takeoff, he sent a flapping-wing drone through the upward-facing fans, which crashed as soon as it encountered them. \u00a0 \u00a0<\/span><\/p>\n
Petey sailed through the wind gusts without seemingly any movement at all. Or did he? \u00a0 \u00a0<\/span><\/p>\n
Raghav set up four high-speed cameras near the flight zone, tracking multiple points on Petey\u2019s body for each test flight. When looking at it with the naked eye, it appears that the perturbations didn\u2019t impact the bird, but when the cameras were slowed down, Raghav learned that Petey was performing several adjustments. One hypothesis is that Petey reduces his wing pitch angle to reduce the force the gust will induce on it. \u00a0<\/span><\/p>\n
\u201cIt\u2019s all instinctive for the bird,\u201d Raghav said. \u00a0 \u00a0<\/span><\/p>\n
Vrishank Raghav, associate professor in the Department of Aerospace Engineering, stands next to Joel Jacobson (center) and Gabe Hallmark (right) of the Auburn University Raptor Center and Petey, the red-tailed hawk. Raghav tracked the flight patterns of Petey to learn how birds smoothly adjust to nature\u2019s perturbations.<\/figcaption><\/figure>\n A mathematical model was created based on Petey\u2019s flights and information tracked from the cameras to learn when the wind speed (or low-gust ratio) is lower than Petey\u2019s flight speed \u2014 the model can determine his flight path. However, the model fails to accurately predict the flight path when the wind speed or disturbance exceeds the bird\u2019s flight speed. <\/span><\/p>\n
\u201cThis leads us to believe the bird is doing something beyond just pitching its wings down to mitigate the effects of the adverse environment,\u201d Raghav said. \u201cThere\u2019s still plenty to learn, but we have taken the first step.\u201d \u00a0 \u00a0<\/span><\/p>\n
Raghav\u2019s research was cited on Physics World\u2019s website<\/a>, which is one of the most recognized physics websites worldwide. This work was also recently accepted for publication in Bioinspiration & Biomimetics<\/a>, a peer-reviewed journal that publishes research involving the study and distillation of principles and functions found in biological systems developed through evolution. \u00a0<\/span><\/p>\n
Another challenge Raghav\u2019s team faced was not related to math or science. It was based on Petey\u2019s mood. \u00a0 \u00a0<\/span><\/p>\n
Stevens said the bird\u2019s reaction is typical, adding that there are several factors to consider when working with live animals. \u00a0<\/span><\/p>\n
\u201cAny live animal is going to be unpredictable, regardless of training. Putting the right distraction in front of the most well-trained canine will eventually elicit a reaction,\u201d Stevens said. \u201cBirds are no different. They can be apprehensive in a new environment. We go through a slow acclimation process to make the bird feel more comfortable.\u201d \u00a0<\/span><\/p>\n
First, the bird\u2019s health takes precedence. The college\u2019s veterinarian participates in the process, and Raptor Center trainers help make the course, and the project, more conducive to success. \u00a0 \u00a0<\/span><\/p>\n
\u201cThey are helping with flights by suggesting more space or overhead to make the bird feel comfortable. Also, they can identify a noise or motion that could affect the bird\u2019s ability to perform,\u201d Stevens said. \u201cSomething teeny-tiny sitting on the other side of the room, a particular color or a blinking light, can create some apprehension for the bird.\u201d\u00a0<\/span><\/p>\n
Raghav did all he could to ensure successful flights each day, including having proper protocols covered by the Institutional Animal Care and Use Committee (IACUC) at Auburn University and the U.S. Fish and Wildlife Service. Yet, if Petey didn\u2019t want to fly, there was nothing to be done. \u00a0 \u00a0<\/span><\/p>\n
Trainers would use food as motivation for Petey to fly, which was approximately six times each day. And, sometimes even with food, Petey decided he didn\u2019t want to move. \u00a0 \u00a0<\/span><\/p>\n
Petey, the red-tailed hawk at the Auburn University Raptor Center, flies onto a perch to eat. Vrishank Raghav, associate professor in the Department of Aerospace Engineering, set up several high-speed cameras to track Petey\u2019s flight patterns and learn how birds fly through turbulence caused by nature.<\/figcaption><\/figure>\n \u201cWe had about six good runs each day because after you are done with feeding, the day is over because he\u2019s not going to take off,\u201d Raghav said. \u201cAs expected, he didn\u2019t fly to our will. It depended entirely on the day and other factors inherent to the bird.\u201d \u00a0 \u00a0<\/span><\/p>\n
Stevens said it could be more than hunger. How active was the bird the day before? Is it a time of the year when the bird would nest or migrate? Is it too warm or too cold? \u00a0<\/span><\/p>\n
\u201cThese factors influence the bird\u2019s behavior and desire to eat and perform,\u201d he said. \u201cThese are things the trainers must consider overcoming or adapting to as they go through their training process.\u201d \u00a0<\/span><\/p>\n
Raghav said the Raptor Center was a significant partner in getting the first steps of this research off the ground. \u00a0<\/span><\/p>\n
\u201cThe collaboration with the Raptor Center was great,\u201d he said. \u201cWe all accommodated each other\u2019s schedules, but when everyone was together, everything went well \u2014 as long as Petey was happy to fly.\u201d \u00a0<\/span><\/p>\n
Stevens also said the collaboration between the Raptor Center and the College of Engineering was a positive experience. \u00a0<\/span><\/p>\n
\u201cAnytime we can be involved in the great work happening across Auburn\u2019s campus, that\u2019s a win for us,\u201d he said. \u201cOf course, there\u2019s the added benefit of the exposure for both the entity performing the work, the research and the Raptor Center.\u201d\u00a0\u00a0<\/span><\/p>\n
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