Rotating Spiral Edge Flames in von Karman Swirling Flows

Experimental observations of rotating spiral flame edges formed during near-limit combustion of a downward-facing, polymethylmethacrylate disk spinning in quiescent air are reported. These flames exhibit similarities to patterns commonly found in quiescent excitable media. The tail rotates rigidly while the tip executes a compound, meandering motion sometimes observed in Belousov-Zhabotinskii reactions. A model assuming a rigid-body rotation with a constant speed of propagation relative to the swirling gas flow generated by the spinning disk predicts the observed spiral shapes well.