Effect of the horseshoe-shaped vortex on heat transfer in vicinity of the leading edge of a cylinder immersed in the turbulent free convection boundary layer on a vertical plate

Abstract

Abstract Measurement data obtained with a thermo-resistance (wolfram-wire) probe for fluctuating temperature field in the front of a finite-height adiabatic circular cylinder disturbing the turbulent free convection boundary layer on a heated vertical flat plate are presented. The measurements were focused on detection of the effects attributed to action of the horseshoe-shaped vortex structures developing in the flow separation zone upstream of the obstacle. It is shown that near-wall air temperature gradients at some measurement positions are dramatically higher, if compared with profiles measured far away from the obstacle. It points in particular to highly intensified heat transfer in the flow region under study. The experimental mean temperature profiles are compared with results of previous RANS- and LES-based numerical studies performed by the authors under conditions that were close to those adopted in the experiments. It is shown that the LES-predicted temperature distributions are in a good accordance with the experimental results. The steady-state solution obtained with the RANS approach partially overpredicts the deformation of the temperature field attributed to action of the horseshoe-shaped vortices, which are substantially unsteady in the reality.