Figure 3
From: Heterogeneous flow inside threads of low viscosity fluids leads to anomalous long filament lifetimes
Revealing the flow inside surfactant filaments. (a) PIV setup for the investigation of horizontal fluid filaments. Schematic illustration of the middle part of the stretching device. The sample (red) is seeded with fluorescent particles and is placed between two circular plates that reached their final position. The lens is focused in the center between both plates and in the mid plane of the thinning filament. (b) Homogeneous flow for viscoelastic fluids. Velocity component in axial filament direction vz inside a viscoelastic 30 mM CTAB/NaSal, R = 7.67 surfactant filament. (c–e) Heterogeneous flow inside a dilute 10 mM CTAB/NaSal, R = 0.5 surfactant filament. (c) Velocity component in axial filament direction vz, with initial displacement, final displacement, and strike time hi = 1 mm, hf = 4 mm, and ts = 0.5 s, respectively. Dashed black lines represent the filament boundaries in the measured plane. (d) Axial velocity component in the lower half of a circular 10 mM CTAB/NaSal, R = 0.5 filament cross-section in the x − y plane. Note that in (b–d) the field of view is much smaller than the filament length. (e) Trajectories of individual tracer particles during thinning over a 20 s time interval inside a 10 mM CTAB/NaSal, R = 0.5 filament. Arrowheads indicate movement directions of the tracers. Dark grey dashed line and light grey dashed-dotted line represent the filament boundaries at t = 0 s and t = 20 s, respectively. A 10× lens and an initial hi = 0.5 mm and final displacement of hf = 1.5 mm are used for this experiment, hence the length of the cylindrical filament between the reservoirs is approximately hf − hi = 1 mm.
