Taylor–Couette flows undergoing orthogonal rotation subject to thermal stratification

• Published in: Physics of fluids (1994) Vol. 33; no. 3
• Main Authors: Khawar, Obaidullah, Baig, M. F., Sanghi, Sanjeev
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.03.2021
• Subjects: Aspect ratio; Computational fluid dynamics; Couette flow; Cylinders; Direct numerical simulation; Domains; Finite difference method; Fluid dynamics; Fluid flow; Heating; Physics; Reynolds number; Rotation; Shear stress; Thermal stratification; Turbulence; Turbulent flow
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/5.0035546

The present study involves direct numerical simulation of turbulent Taylor–Couette flow undergoing orthogonal rotation (gravity and rotation axis are perpendicular) subject to thermal stratification in the radial direction. The simulations were performed based on the finite-difference approach for a radius ratio (η) = 0.5 and an aspect ratio (Γ) = 2π, with Reynolds number ( R e = U θ D ν) ranging from 1000 to 5000. For this wide gap, the role of spatially varying buoyancy forces (Ri ranging from 0 to 0.3) in flow physics has been explored using flow statistics, flow dynamics, near-wall coherent structures, and quadrant analysis. It is observed that near-wall streaks are concentrated at the outflow boundaries of Taylor vortex cells with uniform axial spacing, which decreases with the increasing Reynolds number. Heating of the outer cylinder results in more intense streaks and coherent structures in the half-circumferential domain due to unstable stratification aiding turbulence, while in the other half-domain, stable stratification mitigates turbulence. Quadrant contribution of ur′ and uθ′ reveals that on heating the outer cylinder, there is an increase in turbulence near both the walls due to the enhanced generation of Reynolds shear stresses (sweep and ejection events).