Experimental and numerical investigation of the effect of horseshoe vortex legs on heat characteristics of the downstream region of a circular cylinder-wall junction

Abstract

The present study was investigated experimentally and numerically the effect of horseshoe vortex (HV) legs on the wall heat transfer in a turbulent boundary layer in the downstream region of a circular cylinder-wall junction. The experiments were carried out at three Reynolds number, ReD = 20,0 0 0, 40,0 0 0, and 60,0 0 0 (based on the cylinder diameter and the free-stream velocity) encompassing the turbulent region, while numerical simulations were performed at ReD= 20,0 0 0 only. In the studies carried out, the ratio of cylinder diameter to boundary layer thickness at ReD = 20,0 0 0, 40,0 0 0, and 60,0 0 0 at the point where the cylinder is placed is 2.44, 3.20, and 3.37, respectively. A constant-temperature anemometer and copper-constant thermocouples were used for measurements of velocity and turbulent intensity, and temperature, respectively. The results showed that the flat surface in the downstream region of a circular cylinder-wall junction increased the Stanton number up to 43% compared to the flat surface without cylinders. Furthermore, the increase in the Stanton number at the saddle point at the end of the downstream region of the HV legs showed a peak, while the increase at the separation line point at the beginning of the upstream region is found to be minimum. Another finding observed is that the increase in the Stanton number decreases dramatically from the end of the downstream region of the HV leg to the origin of the upstream region.