Heat and fluid flow of a circular cylinder placed close to a turbulence-generating grid

Abstract

The heat and fluid flow of a circular cylinder placed in the wake of a turbulence-generating grid are studied using large eddy simulations at a Reynolds number of 3900 and a Prandtl number of 0.7. The investigation focused on the wake of the cylinder and compared the results to a uniform inflow case to assess the impact of the highly anisotropic-nonhomogeneous grid-generated turbulence on the cylinder heat and fluid flow. Phase-averaging and spectral proper orthogonal decomposition were applied to analyze the coherent heat and fluid flow fields. The following are the main findings of the cylinder experiencing turbulent inflow, relative to the uniform free-stream case: (i) a highly three-dimensional mean heat and fluid flow, (ii) a 40% shorter recirculation length, (iii) a wake dominated by shedding vortices having lower magnitudes of fluctuations than the uniform inflow case, (iv) delay in flow separation from 87° to 97°, (v) break of the correlation between the wake shedding flow and the flow field at the cylinder front face, (vi) 39% enhancement in the overall Nusselt number, (vii) 100% increase in the local Nusselt number at the rear stagnation point, (viii) higher local heat transfer rate that varies substantially along the span before flow separation, (ix) significantly higher lift force reflected in a 3.7× root mean square lift coefficient and a phase-averaged lift coefficient having a maximum amplitude that is 7×, and (x) an increase in the magnitudes of the advection and production terms of the coherent heat and fluid flow transport equations, especially around the forward and rear stagnation regions.