Natural Convection Around a Horizontal Heated Square-Section Cylinder in an Enclosure: Visualization and Dynamic Characterization of Instabilities by Particle Image Velocimetry

Consider an air-filled square cavity with cold top and bottom walls, adiabatic side walls and a centered heated sharp-edged source (a square-section cylinder). An unstable behavior has been highlighted previously while studying the effects of confinement (with different cylinder sizes) on the topology of the flow. A transition occurs from a bi-dimensional, steady regime to a three-dimensional, unsteady regime when the aspect ratio reaches the value of 0.4 for a Rayleigh number of 5.74 × 10⁴. Time-resolved 2D particle image velocimetry is used to characterize the dynamics of the flow in this configuration. The evolution of the instability is particularly investigated.