Numerical study of free convection in a thin layer between coaxial horizontal cylinders

We consider free convection in 2D and 3D horizontal cylindrical layers with the inner hot outer cold boundary at Ra (Rayleigh number) range (4?103 ÷ 4?105) ratio ? ? 1:20 of layer width to radius. Prandtl number was 0,71, fluid properties were taken for air 293 K. It shown that flow a can be divided into three regions. Stable symmetric convective rolls are formed layer’s upper part; regions transient appear lateral sides; transitional between have an unusual asymmetric shape. The part is organized spatially stable roll pattern. With increase Rayleigh (Ra), pattern becomes suppressed by plume global Nu (the Nusselt proportional 0,0019?Ra0,567 case 0,22?Ra0,192 case. problem provides reasonable estimation up 4?104 overestimates higher number, which agrees Lyapunov exponent values.