Saran crack

Poiseuille flow! Clearly established with link and addition to Wikipedia (fr; damn, how dare they display IPs? Fleury thinks that’s illegal 😉 ). And without need to have a sandwich with a top Extra-cellular membrane (which probably don’t exist and would make a first point for a corrigendum to ask for EPMAG).

Great thing, I learned something new and is well established that the way Fleury see the cellular flow is analogous to a Poiseuille flow.

This is for a viscous liquid flowing against a surface with friction. Hmm, friction. Let’s say that the flow is from left to right. Where do you expect tensile stress? On the left, or on the right? Answer quickly, intuitively, without recourse to your course of physics.

Right! Tensile stress on the right left.

What if there is a membrane under your viscous fluid traveling to the right? What will you expect on the right?


Wrinkles, yep.

Now come on, VF considers the flow to be Poiseuille like and at the same time expect tensile stress at the front of it. Should I ask him his opinion?

Well, not this time. I got a few seconds free so I decided to go experimental. The most difficult part for the setup was to find an eraser. Rare stuff these days. But I did found one. Why an eraser? Because VF use it as an example in EPMAG. I didn’t use it the same way as he did, but I got an eraser. The rest of the necessary stuff include a piece of Saran wrap, some adhesive tape, less then a milliliter of water and a glass covered lab bench.

The bench was cleaned, a few drops of water was set on the clean surface (lubrication factor), covered with a piece of Saran wrap which was fixed on the bench with adhesive tape. The eraser was placed at the center of the setting.

Using the left hand I pushed the eraser from the left to the right, to simulate the flow. While with the right hand I was photographing the result. And here it is annotated, the arrow indicating the direction the eraser was pushed:


You intuition was correct.

Now, what if I pushed harder, so the tensile stress would be superior to the resistance of the wrap foil? One may expect a crack. A Saran crack in this particular case. A Saran crack with eraser. Left or right side?


Well, left side definitively.

Now, WTF has to do the Poiseuille Flow with the eventual crack of the basal lamina of the epiblast? Which would be at the right side if any crack existed. Well, probably nothing at all.

After dropping the top plate, it may be wise to drop the considerations about the Poiseuille flow. Who think differently and why?


5 Réponses

  1. I’m out, on vacation (at least!) for a few days. Sci-Fi ahead. So I don’t think I’ll be connecting for e-mails, blogging or comments.

    And if you are in an anti-teleological mood and want to see a really cute gedankenexperiment visit.

  2. As you often say: « quite cute »

    Was the eraser treated with due respect? You may have problems with the Saran Wrap Protection Society (SWPS)

  3. Sir

    It took you so long to start to only vaguely understand the problem. It took me such a long time to just explain you the content of a scientific paper, while you kept on defamating my work, trying to ridiculing what you did not even understand.

    Now you are starting to do research, with, again, such a negative a priori.

    I am not going to do research with you (you should think for example of the finger which holds the eraser, what holds the substrate, and overall take into account the principle of axction and reaction).

    But please if you do, you are welcome to publish your results in peer-reviewed journals.

    I shrug my shoulders to whatever you say, so low.

    Out you go, Mr. Vekris, and out I go as you so often say.

    I will not come back to this blog, never again.

  4. Great !
    We have a Fleury crack also!

    Really great, I do appreciate.

    NB This isn’t research, just fun with a buggy model 😉

    And in I remain ladies and gentlemen. Haven’t finished yet with EPMAG

  5. […] for me to leave the forum. He avoided to open a personal space to reply to this blog. He said recently that he is done with this blog and he will not visit anymore. I’ll help him keep his […]


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