Natural convection in a cylindrical cavity

Natural convection in a vertical cylinder heated from below is studied experimentally and numerically. The aspect ratio (diameter/height) is 1.3 and we observe convective motions for a Prandtl number of 6.66 and a range of Rayleigh numbers from $1.0\times 10^5$ to $5.0\times 10^6$. This range of Rayleigh numbers includes steady and time-dependent flows. Experimental observations were made with a composed PIV system capable of simultaneously obtaining velocity distributions in two mutually perpendicular planes. The numerical model comprises the solution of the three-dimensional time-dependent Boussinesq equations in cylindrical coordinates. In all cases analyzed, the flows present complex three-dimensional structures and we use the \textit{vortex core} concept as a visualization technique to characterize the fluid motion. Experimental observations are compared with theoretical calculations and quantitative agreement is obtained for steady flow and averaged values in unsteady flow.