The Weissenberg Effect: non-Newtonian fluids climb a rod

Sagemindsays...

It makes sense that stickier substances will climb higher. My logic is not surprised that the glue solution climbed the highest. I'm just not sure if, scientifically speaking, that's what is happening.

"I think" that it depends on the particles and which particles can grab on to the previous ones while being able to slide at the same time. It's like driving in snow, you have to have traction or you can't climb the hill and then you have to have good tires so you can hold on or you slide back down.

I don't have time to go into more detail than that right now so have a great day.


bmacs27says...

My understanding is that the effect has to do with long chain molecules being pulled taut around the spindle. Imagine doing something similar with a tangle of yarn, with one end of the yarn stuck to the spindle. At first, the yarn will make a coil around the spindle, but as the circumference of the coil is increased because of the yarn already coiled, the yarn will start to build up layers of coils vertically around the spindle. If instead you had lots of tiny pieces of yarn, it isn't hard to imagine that the effect wouldn't happen. In fact, you'd probably get something more like a vortex (with little bits of yarn being flung every which way creating a depression).

So it can't just be sticky, because then there will be nothing pulled taut. For example, honey apparently does not work well. Instead I think it needs to be somewhat sticky, as well as composed of long chain molecules that will be pulled tight by the rotation.

messengersays...

I'd be interested to see if it's the whole thing climbing up, or if it's layering new liquid pulled from the bottom on top of the first stuff to get caught, like the yarn analogy. I'd like to see the current "top" place marked in red or something to see what happens to those particles. Actually, I think the red would be pulled to the bar and disappear under the stuff covering it next. In that case I'd like to see the liquid at the widest part at the base of the rod marked red so we could watch it climb, if the yarn effect is in fact what's happening.

kceaton1says...

>> ^messenger:

I'd be interested to see if it's the whole thing climbing up, or if it's layering new liquid pulled from the bottom on top of the first stuff to get caught, like the yarn analogy. I'd like to see the current "top" place marked in red or something to see what happens to those particles. Actually, I think the red would be pulled to the bar and disappear under the stuff covering it next. In that case I'd like to see the liquid at the widest part at the base of the rod marked red so we could watch it climb, if the yarn effect is in fact what's happening.



If possible, do this in another liquid that will stay phased out and then color it; do your experiment. Hell, use light reflective particles and throw a 360 camera/computer capture around it. Good times and simulations too occur!

Darkhandsays...

So I'm guessing the top layer of this liquid is more dense than what is below the surface? It feels like the swirling drill is like a tornado just picking things up and as it goes higher there is more and more resistance from the remaining liquid holding it down.

I imagine if you had just enough liquid (in inches) and you started doing this you could suspend it from the drill in it's entirety as long as you kept spinning it?

Neat nonetheless

Asmosays...

Just a complete stab in the dark here, but I'm guessing as the molecule chains are pulled taut, they provide outward pressure as they contract around the spindle, forcing other molecule chains up/down the spindle. As the base of the spindle is immersed in the liquid, there is already force pressing in from below as material is removed up the spindle, so the liquid goes the only way it can, up.

kceaton1says...

>> ^Asmo:

Just a complete stab in the dark here, but I'm guessing as the molecule chains are pulled taut, they provide outward pressure as they contract around the spindle, forcing other molecule chains up/down the spindle. As the base of the spindle is immersed in the liquid, there is already force pressing in from below as material is removed up the spindle, so the liquid goes the only way it can, up.


I'll have to make a batch to see what it's doing, but it sounds like it's "like" liquids that solidify with kinetic impacts (or as you said it more or less).

kceaton1says...

Also, almost any thick substance like pancake or cake batter will do this (with electric beaters--@Asmo 's comment applies here too)). Just go make some!

Now, I must fulfill my quest of getting Coke™ to do this (with a lot of added material).

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