This idea (G. Campbell, personal communication, 2010) is
based on the assumptions of having an infinitely long cylin-der, instant redistribution of heat within a cross section of the
cylinder, and forced convection on the outside of the cylinder.
Forced convection dominates when the buoyancy force parameter, also known as the Archimedes number, Ar, is much
smaller than one. For a cylinder of diameter d (m)