Counter-rotating Taylor-Couette flows with radial temperature gradient

In the present work, counter-rotating turbulent Taylor-Couette flows with radial temperature gradient have been studied as an extension of previously studied simple-rotating turbulent Taylor-Couette flows. The rotation axis is orthogonal to the gravity vector. Direct Numerical Simulations (DNS) have been carried out for Reynolds number ranging from 1000 to 5000 and Richardson number varying from 0 to 0.4. The effect of variation of Reynolds number and Richardson number on the flow statistics, flow dynamics, and near-wa l l coherent structures are studied. For neutrally buoyant cases, near-wal l coherent structures exist near the inner and the outer wall, with the core being almost vortex-free. With an increase in Richardson number, more dense and finer vortical structures spread out in the core in ha l f the circumferential domain only. This behavior is due to the spatial stable or unstable stratification in the azimuthal direction, leading to the generation of turbulence in the lower ha l f of the domain and mitigation of turbulence in the upper hal f of the domain. Further, the turbulent kinetic energ y (TKE) budget analysis reveals an increase in turbulence on heating the outer cylinder w a l l due to an increase in the production term. Heating the outer cylinder wa l l leads to a slight decrease in skin friction for the inner cylinder.