#heleshawcell — Public Fediverse posts

Flow Behind Viscous Fingers

Nature is full of branching patterns: trees, lighting, rivers, and more. In fluid dynamics, our prototypical branching pattern is the Saffman-Taylor instability, created when a less viscous fluid is injected into a more viscous one in an confined space. Most attention in this problem has gone to the branching interface where the two fluids meet, but recently, a team has examined the flow away from the fingers by alternately injecting dyed and undyed fluid to visualize what goes on. That’s what we see here. Notice how the central dye rings, far from the branching fingers, still appear circular. Yet, even a few centimeters away from the fingers, the dye is starting to show ripples that correspond to the fingers. That’s an indication that the pressure gradient generated at the tips of the fingers is pretty far-reaching! (Image and research credit: S. Gowen et al.)

#flowVisualization #fluidDynamics #HeleShawCell #physics #SaffmanTaylorInstability #science #surfaceTension

If you sandwich a viscous fluid between two plates and inject a less viscous fluid, you’ll get viscous fingers that spread and split as they grow. This research poster depicts that situation with a slight twist: the viscous fluid (transparent in the image) is shear-thinning. That means its viscosity drops when it’s deformed. In this situation, the fingers formed by the injected (blue) fluid start out the way we’d expect: splitting as they grow (inner portion of the composite image). But then, the tip-splitting stops and the fingers instead elongate into spikes (middle ring). Eventually, as the outer fluid’s viscosity drops further, the fingers round out and spread without splitting (outer arc of the image). (Image credit: E. Dakov et al.; via GoSM)

https://fyfluiddynamics.com/2024/04/evolving-fingers/

#2024gosmp #flowVisualization #fluidDynamics #HeleShawCell #instability #nonNewtonianFluids #physics #SaffmanTaylorInstability #science #shearThinning #surfaceTension #viscosity #viscousFingering