Self-sustainment of coherent structures in counter-rotating Taylor–Couette flow

We investigate the local self-sustained process underlying spiral turbulence in counter-rotating Taylor-Couette flow using a periodic annular domain, shaped as parallelogram, two of whose sides are aligned with cylindrical helix described by pattern. The primary focus study is placed on emergence drifting-rotating waves ({\sc drw}) that capture, relatively small main features coherent structures typically observed developed turbulence. transitional dynamics subcritical region, far below first instability laminar circular Couette flow, determined upper and lower branches {\sc drw} solutions originated at saddle-node bifurcations. mechanism whereby these self-sustain, chaotic they induce, conspicuously reminiscent other shear flows. Remarkably, properties persist even Reynolds number increased beyond linear stability threshold base flow. Simulations narrow parallelogram domain stretched azimuthal direction to revolve around apparatus full turn confirm vortices eventually concentrate into localised resulting statistical steady state satisfactorily reproduces qualitatively, certain degree also quantitatively, topology calculated large sufficient aspect ratio representative real system