ASCII Fluid Dynamics

This is really cool.

ASCII fluid dynamics. You didn't know you wanted to see this, but you do.https://t.co/DNpdVUM6dr

— ℝafael Bailo (@rtsbailo) May 31, 2019

Tales from the ArXiv: Low and High Mason Numbers

Here is a new paper on the ArXiv.

Here is a quote from the abstract: In the limit of low Mason number, the dynamical system admits a periodic solution in which the magnetic moment of the swimmer tends to align with the magnetic field. In the limit of large Mason number, the magnetic moment tends to align with the average magnetic field, which is parallel to the axis of rotation.

I operate in the limit of low Mason number, and I claim that this limit is singular.

The Physics of Croissants

The January 2018 issue of Physics Today has a short article about the physics of croissants. Yummy!

Also, check out the lovely contact network in the two-dimensional contact network that one can see in the picture.

Update: Great minds think alike!

You know you've been thinking too much about 2D networks when your immediate thought, and also @masonporter 's, is to analyze the centrality of a croissant. https://t.co/uvVGfaD5Kk

— Karen Daniels (@karenedaniels) January 4, 2018

Fake µs

I am very amused by the title ("Fake μs: A cautionary tail of shear-thinning locomotion") of this paper.

It's too bad, though, that "µ" is the standard notation for kinematic viscosity, as the title would be even more amusing with the notation "𝜈" for dynamic viscosity. It would then be "Fake 𝜈s". In any event, I approve! (And things are open for a sequel paper about dynamic viscosity.)

Also, I like viscous puns.

I previously used a variant of this pun, as you can see below.

I am spreading fake gnus. (This had to be done.) pic.twitter.com/eUcmp3qouZ

— Mason Porter (@masonporter) February 11, 2017

Update (8/31/17): Thanks to Peter Mucha for the comments about kinematic versus dynamic viscosity. This helped me improve my comments above.

Every Sperm is Sacred: Mathematical Edition

Here is a newspaper article about recent research on the fluid mechanics of swimming sperm.

(Tip of the cap to Alan Champneys.)

Fun at the APS Fluid Dynamics Meeting

They're clearly going to have some fun over at the American Physical Society's fluid dynamics meeting this year. There is a session called "Disgust: The Fluid Dynamics of the Gross".

A New Hypothesis About the Physics of Knuckleballs

A new paper in New Journal of Physics proposes a new hypothesis about the physics of knuckleballs.

(Tip of the cap to Science News.)

Message in a Bottle

Sending an SOS to the world pretty much is replying-all.

(And one could also bring up passive tracers.)

The Fluid Dynamics of Sheep

By the way, sheep are a fluid.

Also see one of my previous blog entries.

The Physics of Chocolate Fountains

Here is a delicious exploration of the fluid mechanics of chocolate fountains.

(Tip of the cap to Aya Khaled Al-Zarka.)

Creating a "Urine Black Hole"

One of these years, I ought to go to the APS fluids meeting just to see talks like this.

Oldest Known Message-in-a-Bottle

Recently, the oldest-known message-in-a-bottle resurfaced. It's a really cool story---including the reasons for releasing a bunch of bottles a century ago.

This story necessitates an obvious joke that refers to The Police, and indeed the author of the article to which I linked dutifully included it.

Headline: "Mathematicians Discover How Many Licks It Takes to Get to the Center of a Tootsie Pop"

Well, people have been wondering how many licks it takes to get to the center of a Tootsie Pop, and now some applied mathematicians at New York University have estimated that it takes about 1000 licks. The main reason behind the study is in fact a rather serious one:

The study was done to explore the effects of dissolving materials within a fluid flow, such as rocks in geological environments and pills for pharmaceutical applications. The lollipop angle was just a fun side effect.

(Tip of the cap to whoever posts on Facebook for SIAM .)

Tales from the ArXiv: A Poetic Opening

This paper's topic isn't my cup of tea (or, rather, coffee), so to speak, but its abstract has among the best opening sentences that I have ever seen in a scientific paper: When drinking a cup of coffee under the morning sunshine, you may notice white membranes of steam floating on the surface of the hot water.

I approve!

Update: I do actually find fluid mechanics fascinating --- and this was true even before I joined the applied math group at Oxford --- even though it is not a topic on which I have (yet) published. However, the 'cup of tea' pun still applies and absolutely had to be part of this blog entry. (Also, in general, I am fond of papers that just start with some everyday phenomenon and try to figure out what's up.)

Tales from the ArXiv: The Cheese Flows Alone

I just noticed a new paper on the arXiv with the following eye-catching title: Quantifying thermally induced flowability of rennet cheese curds

I think I might smell an Ig Nobel prize in the authors' future...

The Physics of Ants

Apparently, a collection of fire ants can act either as a fluid or as a solid. Check out the video in the New York Times article to which I just linked. It's way cool.

(Tip of the cap to whoever posts for APS Physics on Facebook.)

Update (12/21/13): As Jimmy Lin points out, you can also make some really cool sculptures by pouring molten aluminum down anthills. Seeing this makes me want data from Anthill Art to complement our study of a rabbit warren in this paper. Notice that the depicted fire ant colonies have a much more complicated network structure than the carpenter ant colonies.

The Fluid Dynamics of Minimizing "Splashback"

Wow, fluid dynamicists sometimes study some really fun problems, like the fluid dynamics of urinating and trying to minimize "splashback". As some physicists have discovered using their patented "Water Angle Navigation Guide" (note the acronym), one of the keys to reducing splashback is to use a narrow angle of attack. (Note: Do not confuse this with "backside attack" from organic chemistry.)

The physics of urination seems to have become a popular research topic lately. It looks like competition for an Ig Nobel prize is going to be pretty stiff.

(Tip of the cap to whoever posts for Physics Today on Facebook, and thanks to Martin Gould for pointing out the acronym above. I actually missed that when I first read the article.)

Tales from the ArXiv: Universal Law of Urination

I'll look at this paper in more detail tomorrow after I get some sleep, but this arXiv paper is a doozy. Here are the details.


Title: Law of Urination: all mammals empty their bladders over the same duration

Authors: Patricia J. Yang, Jonathan C. Pham, Jerome Choo, David L. Hu

Abstract: The urinary system evolved to eject fluids from the body quickly and efficiently. Despite a long history of successful urology treatments in humans and animals, the physics of urination has received comparatively little attention. In this combined experimental and theoretical investigation, we elucidate the hydrodynamics of urination across five orders of magnitude in animal mass, from mice to elephants. Using high-speed fluid dynamics videos and flow-rate measurement at Zoo Atlanta, we discover the "Law of Urination", which states animals empty their bladders over nearly constant duration of average 21 seconds (standard deviation 13 seconds), despite a difference in bladder volume from 100 mL to 100 L. This feat is made possible by the increasing urethra length of large animals which amplifies gravitational force and flow rate. We also demonstrate the challenges faced by the urinary system for rodents and other small mammals for which urine flow is limited to single drops. Our findings reveal the urethra evolved as a flow-enhancing device, enabling the urinary system to be scaled up without compromising its function. This study may help in the diagnosis of urinary problems in animals and in inspiring the design of scalable hydrodynamic systems based on those in nature.


Let me especially point out the following sentence (which is comedy gold): "Despite a long history of successful urology treatments in humans and animals, the physics of urination has received comparatively little attention."


(Tip of the cap to I Fucking Love Science, who posted a popular article about this arXiv paper on Facebook.)


Update: Courtesy of Marc Abrahams, here is what Annals of Improbable Research's blog had to say about this (and about other topics in bodily fluid dynamics).

Liquid Sculpture Photography

Markus Reugels has produced some really awesome high-speed liquid sculpture photography. For example, see the gorgeous works on this page and this page.

Naturally, this should remind you of the Gallery of Fluid Motion, which is usually a big win, as well as of research by certain people (of whom my OCIAM colleagues will certainly be familiar). Sometimes, fluid mechanics can indeed produce some pretty damn awesome stuff!

(Tip of the cap to Jimmy Lin.)

Fluid Dynamics and Penguin Huddling

Recently published in the journal PLoS One is a mathematical model for penguin huddling that takes some inspiration from fluid dynamics. I know the third author (Arnold Kim), who I met when I interviewed for a faculty position at UC Merced in 2005 (and of whom I had heard before then).

(Tip of the cap to whoever does the posts for American Physical Society on Facebook.)