Experimental investigation of the velocity field in free convection from a horizontal disk using an LDV measuring technique

ABSTRACT Natural convection in fluorocarbon liquid FC-72 from an isothermal horizontal upward facing disk has been experimentally investigated. The velocity field arising from the horizontal surface has been studied using the two velocity components Laser Doppler Velocity measuring technique, a non intrusive technique well suited for the low velocities found in free convection. The experimental data concern the flow field above a 30 mm diameter copper disk immersed in the dielectric liquid at atmospheric pressure. The main results consist in the description of the flow field on the diametral plane at various heights above the heated surface for different temperature values. The pointwise velocity measurements at different locations have given mean velocity profiles and turbulence properties of flow. Point velocity values at the edges of the thermal wake and flow visualizations have shown a vortex structure very similar to the ring vortex structure in an axisymmetric turbulent jet. The experiments were carried out in a range of Rayleigh number values including transition and turbulent flow regime.