Direct numerical simulation of inertio-elastic turbulent Taylor-Couette flow

The flow physics of inertio-elastic turbulent Taylor-Couette flow for a radius ratio of 0.5 in the Reynolds number (Re) range of 500 to 8000 is investigated via direct numerical simulation. It is shown that as Re is increased the turbulence dynamics can be subdivided into two distinct regimes: (i) a low Re <= 1000 regime where the flow physics is essentially dominated by nonlinear elastic forces and the main contribution to transport and mixing of momentum, stress and energy comes from large-scale flow structures in the bulk region and (ii) a high Re >= 5000 regime where inertial forces govern the flow physics and the flow dynamics is mainly governed by small-scale flow structures in the near-wall region. Flow-microstructure coupling analysis reveals that the elastic Gortler instability in the near-wall region is triggered via significant polymer extension and commensurately high hoop stresses. This instability gives rise to small-scale elastic vortical structures identified as elastic Gortler vortices which are present at all Re considered. In fact, these vortices develop herringbone streaks near the inner wall that have a longer average life span than their Newtonian counterparts due to their elastic origin. Examination of the budgets of mean streamwise enstrophy, mean kinetic energy, turbulent kinetic energy and Reynolds shear stress demonstrates that increasing fluid inertia hinders the generation of elastic stresses, leading to a monotonic reduction of the elastic-related effects on the flow physics.

Automated summary

The flow physics of inertio-elastic turbulent Taylor-Couette flow with a radius ratio of 0.5 in the Reynolds number range of 500 to 8000 was investigated through direct numerical simulation. The study revealed two distinct regimes of turbulence dynamics as Reynolds number increases, with either nonlinear elastic forces or inertial forces dominating the flow physics in the low and high Reynolds number regimes, impacting the flow structures in the bulk and near-wall regions differently. Examination of the flow-microstructure coupling analysis showed the triggering of elastic Gortler instability in the near-wall region, leading to the formation of small-scale elastic vortical structures known as elastic Gortler vortices with longer average life span compared to their Newtonian counterparts.