Dr. Reetesh Ranjan joined the College of Engineering and Computer Science faculty in 2019. Photo by Angela Foster.
At the University of Tennessee at Chattanooga, research reaches from the lab to the launchpad.
Dr. Reetesh Ranjan, an associate professor in the Department of Mechanical Engineering, develops and applies multi-scale models of turbulence, a longstanding challenge in fluid dynamics with applications in combustion and energy conversion, rocket propulsion, high-speed aerodynamics and stratified ocean flows.
Over the years, his research has received support from several federal agencies, including the National Science Foundation, the Office of Naval Research and the Air Force Office of Scientific Research. He has collaborated with researchers across leading institutions, including the Georgia Institute of Technology, the University of Central Florida, the University of Alabama in Huntsville, the University of Cincinnati and the Air Force Research Laboratory.
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Why did you choose engineering?
“I wanted to become an engineer from an early age. I was always fascinated by how things work, particularly in mechanical engineering, where you can design and build systems that solve real-world problems, from everyday technologies to advanced systems like engines and aircrafts.
“Growing up, I was especially fascinated by mechanical and aerospace applications, and I dreamed of becoming an engineer. My interest was also shaped by my father, who was an electrical engineer. He encouraged my curiosity through hands-on projects and would involve me in activities like building small windmill models that demonstrated electricity generation for school projects. Those experiences sparked my fascination with creating and understanding how things work. I would take apart toys just to see what was inside and then put them back together. Over time, that curiosity evolved into a desire not just to understand existing systems, but to learn how to design and build them myself.”
Could you explain the research you are currently working on?
“I would explain one of the topic areas that I am currently working on. It is focused on the development and application of reduced-order models for the simulation of rocket combustion.
“Think of a rocket engine: fuel is burned inside a combustion chamber to generate the thrust needed for launch. Even for relatively simple fuels like natural gas or methane, combustion is far more complex than what we learn in introductory chemistry. The process involves hundreds of chemical reactions and interactions across multiple scales. While we can build experimental systems and test them, those experiments are extremely expensive and time-consuming. Instead, we use high-performance computing to simulate the complex physics that govern combustion processes.
“However, even the most powerful supercomputers in the world cannot fully capture all the fine-scale phenomena that occur during combustion, especially in extreme environments like a rocket propulsion system. The computational cost remains a major challenge.
“My research focuses on developing advanced models that can capture the essential physics of these processes while requiring significantly fewer computational resources. These models enable faster and more efficient simulations without sacrificing accuracy. The goal is to achieve realistic predictions at a fraction of the computational cost, making high-fidelity simulations more accessible for engineering applications.”
In 2024, Dr. Ranjan earned national recognition from the American Institute of Aeronautics and Astronautics, serving as an AIAA Class of 2025 Associate Fellow.
Why does turbulence interest you?
“I first became interested in turbulence during an undergraduate course. At my institution, mechanical engineering students could choose from several electives, and because I was fascinated by aerospace engineering, I decided to take most of my electives in that area. During the first semester of my junior year, I was introduced to turbulence. I quickly realized that it was one of the most fundamental and challenging unsolved problems in fluid mechanics. The complexity of the physics involved immediately captured my interest, and I was hooked from that very first course.
“Around the same time, a visiting faculty member from Germany came to India and presented results from a turbulence simulation. Seeing those large-scale simulations displayed on a huge screen was fascinating, but what stood out even more was his discussion of the remaining challenges and unanswered questions in the field.
“I was already drawn to fluid mechanics, and turbulence represented the ultimate challenge within that discipline. When I applied to graduate programs, I looked for institutions with strong fluid mechanics research programs, which led me to the University of Illinois at Urbana-Champaign. That experience deepened my interest in turbulence, and I have continued exploring this challenging and fascinating field ever since.”
What advice do you have for students interested in engineering research?
“Undergraduate education provides students with a strong foundation in the fundamentals, but research offers an opportunity to explore how that knowledge can be applied to solve complex problems. I have mentored several undergraduate students, high school students, and even exceptionally talented younger students, and my advice to them is to get involved in research early.
“Throughout their four years as undergraduates, I encourage students to participate in two or three research projects, ideally exploring different topics and working with different faculty members. At that stage, many students may not yet know what they want to pursue as a career or whether research is the right path for them. Experiencing different areas of research helps them discover their interests and better understand their strengths.
“Research is not necessarily the right fit for everyone, and that is perfectly fine. Society needs people with diverse skills and career paths, for example, engineers, managers, researchers, professors, and many others. The key is for students to explore different opportunities and find the path that best aligns with their interests and goals.”
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College of Engineering and Computer Science
Department of Mechanical Engineering
