Flow regime transitions for Aiding flow around a heated cylinder: A numerical and experimental investigation

Experiments and numerical simulations were performed to examine the interplay between buoyancy and momentum effects for mixed convection flow around a 13.4 mm diameter cylinder in water. PIV and LIF measurements were made to obtain experimental velocity and temperatures over a Ri range from 0 to 9. LES models were validated against the measured experimental conditions and then used to numerically study the parametric behaviour over a wider range of conditions. The CFD model was found to perform well, with a small tendency to over predict temperature and velocity measurements for higher buoyancy conditions, Ri > 1.9. Using the experimental LIF results, three flow regimes around the cylinder were identified, grouped, and made into a flow regime map. From this, two sets of transition criteria were developed and proposed to predict the collapse of the recirculation zone and the total suppression of vortex formation. This was done via observations from the experimental data and additional CFD simulations to examine the separate effects of fluid properties and incident turbulence levels, both of which were shown to influence vortex suppression significantly. The criteria proposed was found to accurately capture the visually observed flow regimes experimentally in water.