Numerical investigation of double-diffusive (natural) convection in vertical annuluses with opposing temperature and concentration gradients

Double-diffusive convection in vertical annuluses with opposing temperature and concentration gradients is of fundamental interest and practical importance. However, available literature especially for higher Rayleigh numbers beyond Ra ⩽ 10 5 is sparse. In this study, we investigated double diffusion induced convection up to Ra = 10 7 using a simple lattice Boltzmann model. Thanks to the good stability of the present model, a modest grid resolution is sufficient for the present simulations. The influences of the ratio of buoyancy forces 0.8 ⩽ N ⩽ 1.3 , the aspect ratio 0.5 ⩽ A ⩽ 2 and the radius ratio 1.5 ⩽ K ⩽ 3 on heat and mass transfer characteristics are discussed in detail.