Near-wake behavior of a heated circular cylinder: Viscosity-buoyancy duality

The alteration of the bidimensional wake behind a heated circular cylinder at low Reynolds numbers has been investigated experimentally when buoyancy effects are added to the viscous effects. The experimental apparatus is essentially composed of a hydrodynamical tunnel in which the flow is ascensional and a vortex-shedding cylinder that is placed in the cross flow, electrically heated, and limited at its ends by the walls of the test section. Velocity and temperature fields obtained respectively by laser Doppler velocimetry and thermocouples pointed out the configurations of forced and natural convection with respect to a critical heat input and how they rule the wake when it is dominated, on the one hand, by viscosity and, on the other hand, by gravity. The role of the heating has been found not only to accelerate the wall boundary, but also to increase the velocity in the near-wake region. The results suggest that the behavior of the vortex shedding strongly depends on the heat input, which is how the vortex street can be set off or completely suppressed. (C) Elsevier Science Inc., 1997.