@jnandeep.bsky.social (@poftwente.bsky.social) discussing his master thesis project on singularities with surfactants at the Max Planck meeting. How do surfactants influence coalescence of sessile drops? Teaser talk as Jnan explores the different dynamics across the Peclet-Marangoni parameter space

At moderate impact velocities and low viscosity, a singular flow focusing causes the second peak to exceed the first. This narrow ‘island’ vanishes if viscosity grows or if the impact is too energetic, quenching the focused jet.

Near rebound, a Worthington jet forms within the retracting drop and induces a second force peak. Its amplitude depends on viscosity, impact speed, and surface tension, linking inertial flow focusing to capillarity and viscous dissipation.

Join me on Jan 30 (4 PM CST) at @UIUC for my seminar on how polymeric liquids can be the “Drosophila” of unsteady continuum mechanics—revealing how polymers reshape free-surface instabilities (drops, bubbles, jets).
Abstract: tinyurl.com/23dnlup9
Please DM or email me for details on how to join!

🌀 Finally, the Droplet-B regime at high De (fixed Ohp) resembles Newtonian-like behavior again, where jets form and pinch off at the base. Surprisingly, the elastic stresses are too low to prevent this, highlighting the complexity of EVP fluid dynamics. [5/5]

💧 In the No Pinch-Off regime, at moderate De, jets form but do not break into droplets. Elastic stresses balance the capillary forces--thanks to slow elastic stress relaxation. Plasticity has no impact here. This is analogous to the jet suppression we further elucidate in tinyurl.com/2dbpky9t
[4/5]

🔧 The second regime, No Jet, is observed at high J and low De. Here, increased plasticity prevents jet formation due to enhanced apparent viscosity, leading to a non-flat final shape as the cavity motion slows down. [3/5]

🔍 We identify four distinct regimes of bubble bursting in EVP media, characterized by varying Deborah (De) and plastocapillary (J) numbers. The first regime, Droplet-A, occurs at low De and J, where the behavior resembles Newtonian fluids, producing droplets from the Worthington jet. [2/5]

🌊 New work alert! When champagne bubbles meet elastoviscoplastic (EVP) media! 🚀
With @poftwente.bsky.social, @utwente.bsky.social @kthuniversity.bsky.social and UvA, we explore the role of elasticity and yield stress.
@arivazhagangb.bsky.social, @mazi1.bsky.social , R. Vinuesa, & O. Tammisola
[1/5]

@zaleski.bsky.social congratulations.

And thanks for a wonderful time at UTwente. To many more adventures for you and some of them together ❤️