Large-eddy simulation of non-isothermal flow over a circular cylinder

In the present work, flow around a heated circular cylinder, at a Reynolds number of Re = 3900, is investigated using large-eddy simulation (LES). Large differences in temperature, 25 degrees C, 100 degrees C, 200 degrees C, and 300 degrees C between the cylinder and the oncoming flow are considered, and its effect on the flow and thermal characteristics in the near wake region are studied. The numerical methodology employed is validated for both, the mean and second-order statistics, with the direct numerical simulation (DNS) data available in the literature. The results are analyzed using the mean temperature, velocity, Reynolds stresses, temperature variances, turbulent heat fluxes and energy spectra. The flow and thermal characteristics are studied along the center line in the wake, and in the transverse direction at two locations. The non-isothermal flow characteristics are compared with isothermal flow, to study the effect of temperature on the flow dynamics. Phase-averaging is performed to analyze the regions of turbulence production and convection of heat. It is observed that, the flow characteristics vary non-linearly with the temperature, and the effect is insignificant till a temperature difference of 100 degrees C, however, beyond this significant effect could be noticed. The effect of temperature difference is prominent in the thermal characteristics for all temperature differences, 25 degrees C to 300 degrees C, considered. The transverse component of shear stress fluctuations are observed to be dominant over the stream-wise components at both the locations downstream, thereby enhancing the local mixing of the fluid and hence, the heat transfer. (C) 2020 Elsevier Ltd. All rights reserved.