Influence of Surface Roughness on Heat Transfer and Flow-Induced Vibrations of a Circular Cylinder

Abstract

In this study, two-dimensional numerical analysis was done to investigate the influence of surface roughness on the heat transfer and flow characteristics for a circular cylinder subjected to crossflow. Numerical solution of the URANS and energy equation was sought using Ansys Fluent for the transient analysis at Reynolds number of 100. The roughness was induced in the cylinder surface by considering the sand surface roughness model. Four levels of roughness were studied with the roughness coefficient (Ks/D) varying between 0.01 and 0.06. The cylinder was allowed to move in transverse as well as streamwise direction to study the two-degree of freedom motion. The reduced velocity was varied in the range of 1–10, covering the region with maximum amplitude of vibration. The cylinder was heated at 300°C above the freestream fluid temperature. The numerical model was validated with the results from the literature. The analysis was done in terms of vorticity and temperature contours, Nusselt number, Strouhal number, and lift and drag coefficients. The results indicated that the surface roughness affected the flow characteristics and heat transfer in such a way that Strouhal number increased, while the lift and drag coefficients and Nusselt number decreased with the increase in the surface roughness. However, the effect of Nusselt number was much higher in comparison to the effect on the Strouhal number and lift and drag coefficients.