The ‘flying chimney’, where a paper cylinder floats when set alight, is an interesting phenomenon
that lacks both systematic theoretical and experimental investigation. To investigate the dynamics
of liftoff, an appropriate chimney material was first selected from 22 kinds of traditional Chinese
Xuan paper. Subsequent experiments with this paper, examining the relationship between the
likelihood of liftoff and the height of the air-gap under the cylinder, show the necessity of a gap
and the ideal minimum height required to assure successful liftoff. We experimentally investigate
the cylinder geometry, determining the optimal parameters for height and diameter, and the boundary
conditions for which liftoff can occur. In order to reveal the mechanism of liftoff, a physical
model in which the viscous force is reasonably suggested to be a key kinetic parameter is proposed.
The viscous force can be obtained by substituting the velocity field of heated air-flow into the
constitutive e…