Direct numerical simulation of Taylor-Couette flow: Regime-dependent role of axial walls

Direct numerical simulation (DNS) of the hydrodynamics of Taylor-Couette reactors (TCR) has adopted axial periodic boundary condition (PBC) to significantly reduce the computational cost, however, the consequences remain unexplored. To this end, DNS was conducted to explore the effect of axial walls on the hydrodynamics of TCR. It was found that (i) the effect of axial walls on the torque is regime-dependent: it is negligible at the nonvortical laminar flow regime and the turbulent Taylor vortices regime, its effect is however significant at the laminar Taylor vortices regime; (ii) the maximal effect of axial walls on the torque appears near the critical Ta for the onset of laminar Taylor vortices, where the relative deviation of torques that are obtained using axial PBC and walls can be as high as 15:1%, because of its critical effect on the reactor hydrodynamics, such as the number of Taylor vortices; (iii) the aspect ratio of TCR affects the torque as expected: the larger the aspect ratio, the smaller the effect of axial walls.