Characteristics of the wake behind a heated cylinder in relatively high Reynolds number

Abstract

Thermal effects on the dynamics and stability of the flow past a circular cylinder operating in the forced convection regime is studied experimentally for Reynolds numbers (Red) between 1000 and 4000, and different cylinder wall temperatures (Tw) between 25 and 75°C by means of Particle Image Velocimetry (PIV). In each experiment, to acquire 3000 PIV image pairs, the temperature and Reynolds number of the approach flow were held constant. By adjusting different temperatures in different Reynolds numbers, the corresponding Richardson number was varied between 0.0 and 0.2. With increasing temperature of the wall cylinder, significant modifications of the wake flow pattern and wake vortex shedding process were clearly revealed. By increasing the Richardson number, the high temperature gradient in the wake shear layer creates a type of vorticity with opposite sign to that of the shear layer vorticity. This temperature gradient-vorticity weakens the strength of the shear layer vorticity, causing delay in reaching the recreation point. In addition to the wake characteristics, it is found that, as the Richardson number is increased, the organization of the vortex shedding is altered and the relative position of the first detached vortices with respect to the second one is changed. This change varies the frequency of the shedding process.