Laminar natural convection of air in an open cylindrical cavity has been investigated,for a wide range of geometrical parameters. The conservation equations of mass, momentum and energy in axi-symmetric cylindrical coordinates have been solved, using the CFD code FLUENT. Ideal gas assumption is invoked to account for density variation of air. An extended computational domain has been considered along with the cavity for imposition of proper boundary conditions. The numerical results have been validated with published solutions for rectangular open cavities. Air flow patterns and temperature distributions in the cylindrical cavity have been analyzed with main focus on heat flux distribution and average Nusselt number. It is seen that heat flux distributions in cylindrical cavities are significantly different from that in rectangular cavities. The Nusselt number is high in cavities with low radius values indicating cylindrical cavities are better than rectangular cavities in heat dissipation. Further, the average heat flux and hence Nusselt number decrease as cavity width increases, demonstrating shallow cavities are inefficient in heat dissipation. The average Nusselt number is seen to exhibit two distinct variations with respect to Rayleigh number (/7a). In the conduction regime, it varies as Ra 0.45 and in the convective regime, it varies as Ra 0.15.

Keywords:laminar natural convection, cylindrical open cavity, Navier-Stokes equations, non-Boussinesq approximation.