A finite difference model is used to study the axisymmetric states of an internally heated annulus. Four different heating rates are used to obtain four distinct states of flow, which can be characterized by their heat transfer and loosely described as either conduction- or convection-dominated. The numerical results are interpreted through scale arguments, and by comparison with previous works on the traditional wall-heated annulus, two finite difference computations of which are included.

The conduction temperature scale is found to be 0(λ/k) and the convection temperature scale to be 0(Λ4/5{n̈/(agk3L3)}1/5) where Λ is the heat input; k, n̈ are respectively the thermometric conductivity and kinematic viscosity; L is the width of the annulus, α the coefficient of thermal expansion and g the earth's gravity.