From smooth liquid sheets to chaotic crowns, increasing impact speed transforms droplet splashing.

This work links that transition to Reynolds number and uncovers how instabilities shape droplet size and velocity.

🔗 https://doi.org/10.1063/5.0321372

#dropletimpact #FluidMechanics #splash #reynoldsnumber #physics

Just took a break from my pooter to heave my corpulent meatsack self to my ensuite to belatedly brush my teeth after brekkie. Stooped over my handbasin, doing the doings, i realised that parts of my face were being randomly splashed, so i returned my mind from zooming along the astral plane to consider what might be happening.

Realised that i'd forgotten to turn the cold tap fully off as i began brushing, that the combo of its consequent partial valve opening, the cooler than usual day, & the local water pressure today had combined to make the resultant waterflow's #ReynoldsNumber fully turbulent, not laminar. Furthermore, the ensuing randomness of its flow in this mode was such that often it was striking the basin drain grate grills rather than falling cleanly thru the gaps, & was rebounding aka splashing. Finally, my stoop was sufficient that my face happened to be in just the right range to intersect with this mild local splashing.

These contemplative revelations pleased me. It was a nice little low-key local demonstration that no matter the pomposity, arrogance, & suicidal determination of the ridiculous human species, the principles of #physics, #thermodynamics, #fluidmechanics, & #chaostheory will always prevail.

But i expect such thoughts regularly cross the minds of most peeps as they do their routine ablutions... 🤷‍♀️ 🤭 😜

#existentialism #misanthropy #ClimateCrisis #science #wearetotallyfscked

Turbulent flows feature swirling eddies over a range of sizes — the larger the size range, the higher the Reynolds number. In this satellite image, sediment highlights these eddies in shades of turquoise, showing off the complexity of the flows created where rivers, ocean, and tides meet. The eddies we see here stretch from kilometers in width down to a handful of meters, but the flow’s turbulence persists down to millimeter-scales before viscosity damps it out. (Image credit: L. Dauphin; via NASA Earth Observatory)

https://fyfluiddynamics.com/2024/08/sediment-swirls/

#eddies #flowVisualization #fluidDynamics #fluidsAsArt #physics #ReynoldsNumber #science #sedimentation #turbulence

#SoftMatter have just published the results of a project that Renato Assante, Davide Marenduzzo, Alexander Morozov, and I recently worked on together! What did we do and what’s new? Briefly…

#Microswimmer suspensions behave in a similar way to fluids containing kinesin and microtubules. Both systems can be described by the same system of three coupled nonlinear #PDEs.

A #LinearStabilityAnalysis of these equations suggests that variations in concentration across the system don’t significantly affect emergent #phaseBehaviour. How then can we explain #experiments that show visible inhomogeneities in #microtubule–#kinesin mixtures, for instance?

With increasing activity, we move away from the quiescent regime, past the onset of #SpontaneousFlow, and deeper into the active phase, where #nonlinearities become more important. What role do concentration inhomogeneities play here?

We investigated these questions, taking advantage of the #openSource #Dedalus #spectral framework to simulate the full nonlinear time evolution. This led us to predict a #novel regime of #spontaneous #microphaseSeparation into active (nematically ordered) and passive domains.

Active flow arrests macrophase separation in this regime, counteracting domain coarsening due to thermodynamic coupling between active matter concentration and #nematic order. As a result, domains reach a characteristic size that decreases with increasing activity.

This regime is one part of the #PhaseDiagram we mapped out. Along with our other findings, you can read all about it here!

low #ReynoldsNumber #turbulence #ActiveTurbulence #CahnHilliard #ActiveMatter #NavierStokes #BerisEdwards #CondensedMatter #PhaseTransitions #TheoreticalPhysics #BioPhysics #StatisticalPhysics #FluidDynamics #ComputationalPhysics #Simulation #FieldTheory #paperthread #NewPaper #science #research #ActiveGel #activeNematic #analytic #cytoskeleton #hydrodynamics #MPI #theory

#SoftMatter have just published the results of a project that Renato Assante, Davide Marenduzzo, Alexander Morozov, and I recently worked on together! What did we do and what’s new? Briefly…

The #hydrodynamic behaviour of inhomogeneous #activeNematic gels (such as extensile bundles of #cytoskeletal filaments or suspensions of low #ReynoldsNumber swimmers) can be described by the time evolution of three coupled #PDEs.

Standard #ActiveGel #theory concludes, from a #LinearStabilityAnalysis of these equations, that fluctuations in concentration don’t significantly affect emergent #phaseBehaviour. However, this leaves #experimental #observations of visible inhomogeneities in #microtubule–#kinesin mixtures unexplained. As we move away from the passive (quiescent) regime, past the onset of #SpontaneousFlow, and deeper into the active phase, #nonlinearities become more important. What role do concentration inhomogeneities play here?

Alongside #analytic techniques, we used an in-house #MPI-parallel code developed within the #Dedalus #spectral framework to investigate. We predict a #novel regime of #spontaneous #microphaseSeparation into active (nematically ordered) and passive domains. In this regime, active flow arrests macrophase separation, which is itself driven by the thermodynamic coupling between active matter concentration and #nematic order. As a result, domains do not #coarsen past a typical size, which decreases with increasing activity. This regime is one part of the #PhaseDiagram we mapped out.

Along with our other findings, you can read all about it here!

#CahnHilliard #ActiveMatter #NavierStokes #BerisEdwards #CondensedMatter #PhaseTransitions #TheoreticalPhysics #BioPhysics #StatisticalPhysics #FluidDynamics #ComputationalPhysics #Simulation #FieldTheory #paperthread #NewPaper #science #research