What caused the Big Bang?

In a new paper appearing today in Science Magazine, researchers detailed the mechanisms that could cause the explosion, which is key for the models that scientists use to understand the origin of the universe.

"We defined the critical criteria where we can drive a flame to self-generate its own turbulence, spontaneously accelerate, and transition into detonation," says Kareem Ahmed, an assistant professor in UCF's Department of Mechanical and Aerospace Engineering and co-author of the study.

"We're using the turbulence to enhance the mixing of the reactions to the point where it transitions into this violent reaction and essentially leads to supernovas, which is exploding stars in simple terms," Ahmed says. "We're taking a simplified flame to where it's reacting at five times the speed of sound."

The researcher uncovered the criteria for creating a Big Bang-type explosion while exploring methods for hypersonic jet propulsion.

"We explore these supersonic reactions for propulsion, and as a result of that, we came across this mechanism that looked very interesting," he said. "When we started to dig deeper, we realized that this is relatable to something as profound as the origin of the universe."

The key is applying the right amount of turbulence and mixing to an unconfined flame until it become self-perpetuating, at which point the flame begins to burn the ingested energy leading to a Mach 5 hypersonic supernova explosion.

Applications for the discovery could include faster air and space travel and improved power generation, including reactions that generate zero emissions as all of the products used in the combustion are converted into energy. The discovery was made by using a unique turbulent shock tube that allowed explosions to be created and analyzed in a contained environment. Ultra-high-speed lasers and cameras were used to measure the explosions and help indicate what factors were needed to reach the point where a flame becomes a hypersonic, violent reaction.

UCF's Propulsion and Energy Research Laboratory, where the research was performed, has the only turbulent shock tube for testing hypersonic reactions in the nation.

Co-authors of the study were Alexei Y. Poludnenko, an associate professor in the University of Connecticut's Department of Mechanical Engineering and the study's lead author; Jessica Chambers, a doctoral student in UCF's Department of Mechanical and Aerospace Engineering; Vadim N. Gamezo, with the Naval Research Laboratory; and Brian D. Taylor, with the Air Force Research Laboratory.

The research was supported with funding from the Air Force Office of Scientific Research. Computing resources were provided by the U.S. Department of Defense High Performance Computing Modernization Program under the Frontier project award, and by the Naval Research Laboratory.

Ahmed earned his doctoral degree in mechanical engineering from University at Buffalo -- The State University of New York. He worked at Pratt & Whitney Military Engines and Old Dominion University prior to joining UCF's Department of Mechanical and Aerospace Engineering, part of the College of Engineering and Computer Science, in 2015. He is a faculty member of The Center for Advanced Turbomachinery and Energy Research, associate fellow of the American Institute of Aeronautics and Astronautics, AFRL Faculty Research Fellow, and a member of UCF's Energy Conversion and Propulsion Cluster.