In 1921 an analysis by von Karman demonstrated that viscous pumping action
occurs when a flat disk is rotated in a fluid of semi-infinite extent. The
rotation draws material inward normal to the disk, forcing it radially outw
ard, thereby causing a swirling motion. A similarity exists near the disk.
in the vicinity of the centerline, such that the radial and tangential velo
city components are proportional to the radius, while all other flow proper
ties depend only on the distance normal to the disk. If the disk is a fuel
and the ambient fluid is an oxidizing gas, then a flat laminar diffusion fl
ame parallel to the disk can be established in the swirling flow drawn in.
Theoretical descriptions of such flames have been developed previously, and
some experiments have been performed, notably for disks of polymethyl meth
acrylate (PMMA) in air. The present contribution provides quantitative meas
urements of burning rates and flame stand-off distances for such rotating d
isks and demonstrates that time-dependent heating of the fuel is important
under these conditions, while nearly steady-state conditions apply in the g
as. The fully steady-state solutions that have been published would apply t
o PMMA only for combustion in oxygen-enriched atmospheres for the sample si
zes and rotational rates of the present experiments.