When a vertical rotating annulus of liquid is subject to a horizontal temperature gradient, provided that the coefficient of kinematical viscosity, ν¯, is not too great and the angular velocity of rotation,Ω is sufficiently high, four distinct regimes of hydrodynamical flow are possible, as shown in previous work by Hide. Only one of these regimes is characterized by symmetry about the axis of rotation. The principal properties of the flow depend largely on the dimensionless parameters Π2≡d/(b−a), Π4gdΔρ/ρ¯Ω2(b−a)2, Π5≡4Ω2(b−a)5/ν¯2d and Π6≡ν¯/κ¯, where d is the depth of the fluid,b and a are the radi of curvature of the surfaces of the annulus, g is the acceleration of gravity, ρ¯ is the mean density of the fluid, Δρ is the density contrast associated with the impressed horizontal temperature gradient and κ¯ is the thermal diffusivity of the fluid. In a diagram with log10Π5 as abscissa and log10Π4 as ordinate, axisymmetric flow is found outside an anvil-shaped region whose upper boundary lies be... Abstract When a vertical rotating annulus of liquid is subject to a horizontal temperature gradient, provided that the coefficient of kinematical viscosity, ν¯, is not too great and the angular velocity of rotation,Ω is sufficiently high, four distinct regimes of hydrodynamical flow are possible, as shown in previous work by Hide. Only one of these regimes is characterized by symmetry about the axis of rotation. The principal properties of the flow depend largely on the dimensionless parameters Π2≡d/(b−a), Π4gdΔρ/ρ¯Ω2(b−a)2, Π5≡4Ω2(b−a)5/ν¯2d and Π6≡ν¯/κ¯, where d is the depth of the fluid,b and a are the radi of curvature of the surfaces of the annulus, g is the acceleration of gravity, ρ¯ is the mean density of the fluid, Δρ is the density contrast associated with the impressed horizontal temperature gradient and κ¯ is the thermal diffusivity of the fluid. In a diagram with log10Π5 as abscissa and log10Π4 as ordinate, axisymmetric flow is found outside an anvil-shaped region whose upper boundary lies be...