PIV investigation of buoyant plume from natural convection heat transfer above a horizontal heated cylinder

This paper presents the results of an experimental investigation of the characteristics of the velocity field above an uniformly heated horizontal cylinder (outer diameter 54 mm) in water. Mean and fluctuating velocity fields are presented for a range of Rayleigh numbers from 2.05E7 to 7.94E7. Circumferential Nusselt number distributions are also presented. Velocity data is compared with existing similarity solutions for turbulent plumes. The flow is initially laminar around the cylinder and undergoes a transition to turbulent flow a distance above the cylinder. The point where transition from laminar to turbulent flow initiates travels upstream towards the cylinder for increasing Rayleigh number.