The effect of a high-speed rotational oscillating cylinder on a heated cylinder

Abstract

This study investigated the effect of a clockwise and counter-clockwise oscillating (control) cylinder on the flow structure and heat transfer on a heated (bare) cylinder placed in the downstream region of the flow experimentally. In this regard, temperature measurements were made regularly for heat transfer analysis. Particle image velocimetry (PIV) technique was used to determine the instantaneous and time averaged flow characteristics such as streamlines (<ψ > ), turbulent kinetic energy (<TKE > ), vorticity contours (<ω > ), the root mean square of streamwise velocity fluctuations < Urms>, and the root mean square of spanwise velocity fluctuations < Vrms >. The effects of oscillating amplitudes and oscillating speed (forcing frequency) on velocity distributions were also analysed at a specified location. The experiments were conducted at the Reynolds number (Re) 5000 based on the diameter of the bare cylinder with two different oscillating amplitudes 8π and 16π and three different forcing frequencies (FR) 3.5, 7 and 14. With the increase of forcing frequencies, it was observed that the wake region became narrower compared to the main cylinder, and then smaller after being moved towards the cylinder wall. In the case of FR = 3.5-16π, the boundary layer separation was found to be prevented by the effect of the oscillating speed and oscillating amplitude, and the dead zone in the rear of the cylinder was completely eliminated. The heat transfer was found to be evenly distributed at almost all points around the cylinder, and to show the best result especially in the rear of the cylinder among all the cases studied. The results obtained from the temperature and PIV experiments were consistent with each other.