#shearthinning — Public Fediverse posts

Baseball’s Mysterious Rubbing Mud

Since 1938, every ball in Major League Baseball has been covered in a special “rubbing mud” harvested from a secret location in New Jersey. Although the league has tried in the past to replace the mud with an alternative, it’s never stuck. Researchers wondered just what makes this mud so special, so naturally, they brought some to the lab to study its composition and rheology.

The mud consists of clay, silt, and sand with a smattering of organic particles. The make-up was pretty typical of river mud in the region, although researchers noted a drop-off in large particle sizes that probably indicates some sieving. In terms of rheology, the mud is shear-thinning, meaning it behaves a bit like lotion. It sits solidly in the hand until it’s deformed, at which point it smoothly coats the surface as a liquid would.

So how does the mud change the baseballs? The researchers found three effects. First, the mud’s shear-thinning allowed it to fill in any pores or imperfections in the ball’s surface, creating a more uniform surface. Second, the dried mud’s residue doubled the ball’s contact adhesion. And, finally, the occasional large sand particles glued to the ball by the dried mud added friction. As the researchers put it, the rubbing mud “spreads like skin cream and grips like sandpaper.” (Image credit: L. Juarez; research credit: S. Pradeep et al.; via EOS)

#baseball #fluidDynamics #physics #rheology #science #shearThinning #sports

“One”

A 4-minute, unedited one-shot video of colorful paint sliding down a sheet? Yes, please.

Beautiful visuals aside, there are some really interesting physics involved here. It’s unclear whether the there’s any change in the speed at which paint gets deposited at the top of the incline over the course of the video, yet we see huge changes in the visual patterns. This happens, in part, because the layer of paint is getting thicker and heavier over time, changing the dynamics of its slide under gravity. There may even be some shear-thinning going on, given that paint is usually non-Newtonian. I can imagine some connections to landslides, avalanches, and other gravity currents with non-Newtonian fluids. (Video and image credit: R. De Giuli)

#fluidDynamics #fluidsAsArt #gravityCurrent #nonNewtonianFluids #physics #science #shearThinning

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