Fig. 4: Velocity field in a medium size constriction.
From: The crucial role of adhesion in the transmigration of active droplets through interstitial orifices
The top row a–e shows the structure of the velocity field v within and in the surrounding of an active droplet crossing a constriction where λ ≃ 0.5, while the bottom one shows its magnitude ∣v∣. The double vortex pattern observed in the unconstrained motile droplet (see Fig. 1g) turns into a single one rotating counterclockwise (a), with magnitude larger near the pillars (f). Once the droplet enters the pore, such vortex shifts towards the center of the drop, while a net unidirectional flow emerges at the front (b, c) and becomes dominant near the exit (d), where it acquires an oscillating structure. During the crossing, the magnitude ∣v∣ remains higher near the pillars (g–i), whereas it considerably decreases at the exit (j), once the double vortex structure is restored (e).
