The dynamics at decreasing temperatures of natural convective motion, and associated heat transfer and mass
flow, are strongly enhanced by the large changes in basic properties such as increasing density and decreasing
viscosity. As a result , the natural convective fluid dynamics of vapours and liquids, both single and multicomponent
in composition, are not the same as fluids at ambient temperatures, being driven by powerful density
gradients up to 1000%/m and local temperature gradients up to 10,000 K/m.