RT Journal Article SR Electronic T1 The structure of the blue whirl revealed JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP eaba0827 DO 10.1126/sciadv.aba0827 VO 6 IS 33 A1 Chung, Joseph D. A1 Zhang, Xiao A1 Kaplan, Carolyn R. A1 Oran, Elaine S. YR 2020 UL http://advances.sciencemag.org/content/6/33/eaba0827.abstract AB The blue whirl is a small, stable, spinning blue flame that evolved spontaneously in recent laboratory experiments while studying turbulent, sooty fire whirls. It burns a range of different liquid hydrocarbon fuels cleanly with no soot production, presenting a previously unknown potential way for low-emission combustion. Here, we use numerical simulations to present the flame and flow structure of the blue whirl. These simulations show that the blue whirl is composed of three different flames—a diffusion flame and premixed rich and lean flames—all of which meet in a fourth structure, a triple flame that appears as a whirling blue ring. The results also show that the flow structure emerges as the result of vortex breakdown, a fluid instability that occurs in swirling flows. These simulations are a critical step forward in understanding how to use this previously unknown form of clean combustion.