structural:expansion
Mathematical models of convection

A number of dimensionless terms have been derived to describe and predict convection, including the Archimedes number, Grashof number, Richardson number, and the Rayleigh number.

In cases of mixed convection (natural and forced occurring together) one would often like to know how much of the convection is due to external constraints, such as the fluid velocity in the pump, and how much is due to natural convection occurring in the system.

The relative magnitudes of the Grashof number and the square of the Reynolds number determine which form of convection dominates. If G r / R e 2 ≫ 1 {\displaystyle {\rm {Gr/Re^{2}\gg 1}}}, forced convection may be neglected, whereas if G r / R e 2 ≪ 1 {\displaystyle {\rm {Gr/Re^{2}\ll 1}}}, natural convection may be neglected. If the ratio, known as the Richardson number, is approximately one, then both forced and natural convection need to be taken into account.