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UMD Researchers Identify Structure of Blue Whirls

By Robert Herschbach

A team of researchers at the University of Maryland and Texas A&M University has identified the structure of “blue whirls,” small, spinning blue flames that produce almost no soot when they burn and are a potential new avenue for low-emission combustion.

Using high-performance computing methods at UMD’s Deepthought2 cluster and other computer systems, the researchers showed that a blue whirl is composed of three flames—a diffusion flame and a premixed rich and lean flame—all of which meet in a fourth structure, a triple flame that appears as a whirling blue ring. The researchers also found that vortex breakdown—a fluid instability that occurs in swirling flows—enables the blue-whirl structure to emerge. Their findings were published yesterday in the journal Science Advances.

“The flame and flow structure revealed by the simulations serves as a fundamental base to further investigate how to create the blue whirl in a more controlled way,” said co-author Xiao Zhang Ph.D. ’20. “It leads pathways to answering more complex questions.”

She and Joseph D. Chung Ph.D. ’20 conducted the research with Elaine S. Oran, TEES Eminent Research Professor at Texas A&M University and previously Glenn L. Martin Professor at UMD’s A. James Clark School of Engineering, and Research Associate Professor Carolyn R. Kaplan of UMD’s Department of Aerospace Engineering,

“Examples of such questions are: How to create blue whirls in different scales? Can we bypass the transitional, sooty, dangerous fire whirl stage and create the stable and clean blue whirl directly? The newly developed algorithms and models also provide great exploring tools to find these answers,” Chung said.

Oran discovered blue whirls in 2016 working with former UMD engineering professors Michael Gollner and Professor Huahua Xiao, now at the University of California, Berkeley and University of Science and Technology in Hefei, China, respectively.

The new study was supported by grants from the National Science Foundation, the Army Research Office, the Army Research Laboratory, the Minta Martin Endowment Funds in UMD’s Department of Aerospace Engineering and the TEES Eminent Professorship at TAMU.

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