Large-eddy simulation of turbulent mixed convection in a vertical annulus with a rotating inner cylinder

Large-eddy simulations of mixed convection in an upward turbulent flow inside a vertical annular pipe with a rotating inner cylinder were performed at Re _Dh = 8900 and Pr = 0.71. The principal objective of this study was to investigate the combined effects of buoyancy and inner wall rotation on the turbulent structures. The incompressible filtered Navier–Stokes equations and energy equations were solved using a mixed fourth and second-order accurate finite difference method. Isoflux wall boundary conditions with low and high heating (buoyancy numbers, Bo = 0.18 and 0.5) were imposed. Two rotation rates (N = 0.1716 and 0.2574) were used and the radius ratio (R*) was 0.5. Various turbulent statistics were obtained to analyze the near-wall turbulent structures. The results show that strong heating of the system with a stationary inner wall causes distortions of the flow structure resulting in reduced turbulent intensities, shear stress, and turbulent heat flux, particularly near the wall. In contrast, rotation of the inner cylinder suppresses this substantial reduction in turbulent statistics.

Keywords:

• Concentric annulus
• Large-eddy simulation
• Mixed convection
• Turbulent rotating flow