Explaining The Behavior of Non-Newtonian Fluids

Beyond the boundaries of established science an avalanche of exotic ideas compete for our attention. Experts tell us that these ideas should not be permitted to take up the time of working scientists, and for the most part they are surely correct. But what about the gems in the rubble pile? By what ground-rules might we bring extraordinary new possibilities to light?

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Explaining The Behavior of Non-Newtonian Fluids

Unread postby jimmcginn » Mon Nov 13, 2017 9:13 pm

Here is a question that I want to invite anybody to weigh in on:
Why do non-Newtonian fluids become structurally rigid when a sudden force is exerted on them?

Example:
ScienceMan Digital Lesson - Physics - Non-Newtonian Fluids
https://www.youtube.com/watch?v=2mYHGn_Pd5M

Question:
Source: https://physics.stackexchange.com/quest ... ed-on-them

You can dip your hands into a bowl of non-Newtonian fluid but if you are to punch it, it goes hard all of a sudden and is more like a solid than anything else. What is it about a non-Newtonian fluid that makes it go hard when having a force exerted on it? How does it go from being more like a liquid to a solid in such a short amount of time? Does it change its state as soon as the force has made contact with it?

Answers:
There are two answers at the stack exchange site. (Edited for brevity.)
1) . . . at some point the spacing between the grains becomes less than the size of a grain. At this point, when you try apply a large force to suspension the starch grains bump into each other and lock together to form a framework. The water in the suspension now has to flow through the small pores in the starch grain "framework" and this requires a lot of force. Hence you can stand on the suspension for a moment. If the apply a small force the water/starch grains move slowly and this gives time for the starch grains to slide around between each other so they will flow.

2) Imagine a velocity gradient in the fluid. Then grains in one layer of the fluid will have to "roll over" particles in another layer of the fluid, colliding with each other as they do so. The steeper the velocity gradient, the more the fluid will tend to "dilate" in the direction normal to the gradient. But once the dilation effect gets sufficiently large, the water's surface tension provides a confining force that resists further dilation. This makes it much harder to maintain the velocity gradient and so the viscosity goes way up.

3) Here is a third explanation from phys.org (it also has videos to demonstrate the phenomena):
https://phys.org/news/2012-07-duo-non-n ... mpact.html
. . . they found that the tiny particles that are normally suspended in the liquid are suddenly jammed together when impacted from above, creating a cone like shape inside the liquid that is dense enough to be described as a temporary solid; as it just as quickly dissolves back to its original state.

Discussion:
What do you think is the best explanation and why?

Is it possible that all three of these explanations harbor a fundamental error? If so, what?

Do you yourself have an explanation for this phenomena?

James McGinn / Solving Tornadoes
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Re: Explaining The Behavior of Non-Newtonian Fluids

Unread postby jimmcginn » Fri Nov 17, 2017 5:25 pm

So, after reading the above post, which of these three do you consider the best explanation:

1) The starch grains bump into each other and lock together to form a framework. The water in the suspension now has to flow through the small pores in the starch grain "framework" and this requires a lot of force.

2) Grains in one layer of the fluid have to "roll over" particles in another layer of the fluid, colliding with each other as they do so. The steeper the velocity gradient, the more the fluid will tend to "dilate" in the direction normal to the gradient. Once the dilation effect gets sufficiently large, the water's surface tension provides a confining force that resists further dilation.

3) Tiny particles that are normally suspended in the liquid are suddenly jammed together when impacted from above, creating a cone like shape inside the liquid that is dense enough to be described as a temporary solid.

4) None of the above.

For me the best answer is #4. But if I was obligated to chose between #1 through #3 I would chose #2 because it at least addresses the right answer.

The right answer is that a three dimensional form of surface tension is created in the fluid when force is applied. Specifically, when force is applied grains of starch actually get between some of the water molecules and force the breaking of ‘weak’ hydrogen bonds simultaneously creating ‘strong’ hydrogen bonds—like air brakes.

To get a better conceptualization of what I mean by this phrase “like air brakes,” I suggest reading the excerpts below and following the links to get a better understanding context of these excerpts.

viewtopic.php?f=10&t=16582#p117062

This notion that H bonds are switches that inherently neutralize other H bond(s) in their vicinity and that the breaking of the H bond, thereby, reactivates these other H bond(s)—like air brakes—was a supposition I developed after I became more fully cognizant of the weak/strong dichotomy. Long before I decided to put pen to paper on all of this and even after I began converting it all to ones and zeros, I would occasionally, come across somebody describing the hydrogen bonding of H2O and I noticed a dichotomy. (It is, essentially, the same dichotomy that was mentioned, briefly, above [ladder of lies].) Sometimes people talked about H bonds and the force that underlies it, H2O polarity, as being strong. Sometimes people talked of them being weak. The strength of H bonds, for example, explained the high boiling point of H2O or the hardness of ice, they would say. The weakness of H bonds, on the other hand, explained the extremely low viscosity (high fluidity) of liquid water and ease by which it evaporates/sublimates. So which is it? Are H bonds strong or are they weak? The literature on H bonding seemed to suggest the existence of weak bonds and strong bonds, but otherwise seemed arcane, confused and completely unhelpful. So I just kind of reverse engineered the understanding that I discussed above. It just seemed to fit the facts. Water molecules were both weak and strong. And H bonds themselves were the switch thereof. But it was not a normal switch, it was some kind of reverse switch—kind of like air brakes. (Not the kind in cartoons. The kind in buses and trains.)

viewtopic.php?f=10&t=16582#p117061

If someone were to take an accounting of the molecules in the atmosphere and enumerated the number of molecules at any point in time that are experiencing or participating in wind-shear and they compared that number to the number of molecules in the atmosphere that were not participating in wind-shear they would find that wind-shear comprises an incredibly small part of our atmosphere. My guess is one tenth of one percent, give or take an order of magnitude. This might bring one to dismiss it as inconsequential. But that would be a mistake. As was indicated previously, it is especially important to be cognizant of the fact that along these boundaries where large bodies of air meet there exists conditional factors that don’t exist anywhere else in the atmosphere: molecules directly impacting each other in a highly directional manner along a usually flat or somewhat flat plane and often over long distances and/or wide areas, sometimes spanning hundreds or even thousands of miles. I conjectured that moist/dry wind-shear would cause the microdroplets along the moist layer to be repeatedly impacted with side-glancing impacts and that would cause them to spin and, well, as they spun centrifugal forces would cause them to elongate into chains of H2O molecules—polymers or threads of H2O—spinning rapidly end over end. This would maximize the surface area of these H2O microdroplets. And, theoretically, this would also turn up the dial on H2O surface tension.

James McGinn / Solving Tornadoes
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