Fig 1.
Experimental set-up with Taylor vortices.
(1) three-segment electrodiffusion probe, (2) shaft, (3) outer cylinder, (4) inner cylinder. The arrows represent flow input and output.
Fig 2.
Front view of ideal three-segment probe with current density.
Fig 3.
Arrangement of three simple probes with a diameter of 0.1 mm.
Fig 4.
Snapshots of films acquired in the present investigation.
For regime abbreviations see Fig 5. Film 1. TV, Ta = 142, Re = 10.5; Film 2. 1V, Ta = 142, Re = 4.2; Film 3. 1+1, Ta = 130, Re = 5.3; Film 4. 0+1, Ta = 112, Re = 10.5; Film 5. 0+2, Ta = 130, Re = 10.5;Film 6. 0+1, Ta = 112, Re = 10.8. Film 7. T+1, Ta = 159, Re = 7.4; Film 8. 0–2, Ta = 142, Re = 8.5; Film 9. 0–1, Ta = 159, Re = 5.05. Film 10. M-1, Ta = 159, Re = 5.05; Film 11. 4–1,Ta = 254, Re = 6.4; Film 12. 3V, Ta = 207, Re = 10.5.
Fig 5.
Regimes observed at different Ta and Re numbers.
Acronyms represent measurement points. The curves sketched between flow regimes are a visual guide, but should not be constructed as sharp boundaries. 0–1 –standing simple helix winding in the same direction as the base flow. 0–2 –standing double helix winding in the same direction as the base flow. 0+1 –simple helix winding in the opposite direction to the base flow. 0+2 –double helix winding in the opposite direction to the base flow. 1+1 –simple helix winding in the opposite direction to the base flow with one azimuthal wave. 3–1 –standing simple helix winding in the same direction as the base flow with three azimuthal waves. 4–1 –standing simple helix winding in the same direction as the base flow with four azimuthal waves. 3–2 –standing double helix winding in the same direction as the base flow with three azimuthal waves. 4–2 –standing double helix winding in the same direction as the base flow with four azimuthal waves. 1V –vortex flow with one predominant azimuthal wave with sudden variation of slope. 3V –vortex flow with three azimuthal waves. 4V –vortex flow with four azimuthal waves. CP–Couette Poiseuille flow. M-1 –simple helix winding and moving in the same direction as the base flow. T+1 –simple helix winding in the opposite direction to the base flow interpenetrated with Taylor vortices. TV–Taylor vortices moving with the axial flow.
Fig 6.
History of wall shear rate components at the outer cylinder of a Taylor vortex flow (TV) at Ta = 142 and Re = 10.5.
The light thick line (yellow online)–total wall shear rate; the darkest line (blue online)–the azimuthal component; and the shadowy line (orange online)–the axial component. The 10 s time corresponds to 18.9 mm of the axial scale.
Fig 7.
History of wall shear rate components at the outer cylinder in a vortex flow with one azimuthal wave having a sudden variation of slope (1V) at Ta = 142 and Re = 3.
The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component. The 10 s time corresponds to 5.26 mm of the axial scale.
Fig 8.
History of wall shear rate components at the outer cylinder of TV flow at Ta = 142 and Re = 5.3.
The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component. The 10 s time corresponds to 9.32 mm of the axial scale.
Fig 9.
Wall shear rate components at the outer cylinder of a helix winding in the opposite direction to the base flow (Ta = 112, Re = 10.5, 0+1).
The axial flow was stopped at 60 s.The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component.
Fig 10.
History of wall shear rate components at the outer cylinder of the standing helix winding in the same direction as the base flow (Ta = 177, Re = 4.2, 0–1).
The axial flow was stopped at 50 s. The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component.
Fig 11.
History of wall shear rate components at the outer cylinder of a helix winding in the same direction as the base flow (Ta = 159, Re = 5.05, M-1).
The axial flow was stopped at 125 s. The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component.
Fig 12.
History of wall shear rate components at the outer cylinder in a standing wavy helix winding in the same direction as the base flow (Ta = 177, Re = 5.1, 4–1).
The axial flow was stopped at 40 s. The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component.
Fig 13.
History of wall shear rate components at the outer cylinder in a wavy vortex flow (Ta = 207, Re = 1.9, 4V).
The light line (orange online)–the axial component; the dark line (blue online)–the azimuthal component. The 10 s time corresponds to the 20.4 mm vortex axial scale.
Fig 14.
Azimuthal component of the wall shear stress.
The dashed light line (red online) represents a supercritical Couette flow and the black line a numerical simulation of a supercritical Taylor vortex flow [35]. Triangles represent Taylor vortices, rectangles indicate helices winding in the same direction as the base flow and circles correspond to helices winding in the opposite direction to the base flow.
Fig 15.
Power spectrum of wavy helices winding in the same direction as the base flow (3–1) after stopping the axial flow (Ta = 254, Re = 8.5).
f1 and f2 stand for frequency of helix rotation and passage of azimuthal waves, respectively.
Fig 16.
Power spectrum of wavy helices winding in the same direction as the base flow (4–1) after stopping axial flow (Ta = 272, Re = 8.5).
f1 and f2 represent the frequency of helix rotation and the passage of azimuthal waves, respectively.