A few weeks ago I submitted a piece to the Journal of Fluid Mechanics’ writing competition. I didn’t win, but I learned some stuff. Today I want to share my piece and what I learned.
As I get deeper into writing, the lines between journalism, communication, and copywriting are getting clearer… and my understanding of where I fit gets blurrier.
The competition asked writers to select a recent paper published in their academic journal and translate it into a 700-word article for general audiences. So my first challenge was to find my article. I read the titles and abstracts of every paper published in the Journal of Fluid Mechanics over the last 6 months and made a list of possible subjects (Pocket was extremely helpful for saving papers for closer reading later). Ideally I wanted an article with general appeal, pretty pictures, significance, and a general wow factor. Being somewhat of a niche journal, I had to be a bit generous when it came to fulfilling those criteria.
Once I had a list of about 20 articles, I started narrowing my options down further. I immediately axed articles without pictures, a clear application, or connection to an everyday phenomenon. This might have been where I lost some points. I’m still learning a lot about pitching stories and finding angles, and I wouldn’t be surprised if the winners had a better strategy or a better eye for a story. Looking back, I probably should have picked something more related to polymers. There are just so many applications there and dynamical similarities to other areas of research (like DNA and other chain-like molecules), but instead I picked the article with the prettiest picture and a historical angle.
Translating the article presented another set of difficult decisions. The article itself was a bit of a doozy, hitting nearly 50 pages in the main text and about a dozen supplemental videos. The paper itself gave a nod to the historical context of the research, in-depth description of the physics, and a hint to the significance of the work, but 700 words is just too few to do all of these things justice. That’s my assessment now. That didn’t stop me from trying to fit all three in though.
If I had a chance to re-submit this, I would reconsider what my “angle” would be. From the beginning I should have identified that I was not writing a #scicomm piece. While I think my talents lie in translating the technical aspects of these papers, I should not have been aiming to teach my readers about fluid dynamics. Likewise, though I like my introduction, I also think I spent too many words here. What I should have focused on was novelty, application, and “selling” the article. Like a lot of writing competitions, this was a way to solicit writers for their blog (ask me about this on twitter). I don’t think it’s a stretch to say the main reason an academic journal hosts a blog is to drive interest in the papers published in the journal. I think that maybe I should have put myself in the mindset of a copywriter.
Live and learn I suppose… Regardless, here is my rejected piece. Enjoy!
Paper Title: Kinematics and dynamics of freely rising spheroids at high Reynolds numbers
Paper DOI: https://doi.org/10.1017/jfm.2020.1104
Word Count: 696
Researchers have classified several ways to rise through buoyancy, and none of them are straight up.
Two objects dropped in a vacuum fall at the same rate. They also follow the same path – straight down. In practice though we rarely drop things in a vacuum. Intuition tells us the size and shape of an object will affect the speed it falls and the drag it produces, but the size and shape affect the object’s path of descent. Yet, while the flipping of a falling penny or the fluttering of a playing card may seem chaotic and unpredictable, a recent study has classified a range of similar behaviors that a spheroid undergoes as it accelerates through a fluid. Their results relate the aspect ratio of buoyantly similar but geometrically disparate objects to the fluttering, tumbling, and helical modes of a rising spheroid through a viscous fluid. The results were published in the Journal of Fluid Mechanics in February of 2021.
Fig. 1: A depiction of the trajectory and orientation of seven different spheroids rising through a fluid at several different stages of their ascent. Multiple images of each particle are superimposed on top of a line that follows the motion of the particles.
Both Galilao and Newton studied this effect using bubbles and falling hog bladders respectively. Though Newton understood objects experience the same acceleration due to gravity, he identified that in practice, drag can make things more complicated. So complicated that researchers are still trying to understand the dynamics of objects pushing through fluids (in Newton’s case, air can be treated like a fluid). The problem is more than esoteric “stamp collecting” though. According to the authors, understanding the movement of particles through a fluid can lead to new techniques for chemical mixing in industrial scenarios as well as in new lab-on-a-chip microfluidic devices. The process is also present in nature in the form of sedimentation in rivers and oceans, as well as the precipitation of snow, hail and rain.
What makes this problem complicated is not the understanding of an exotic and new type of physics; it’s in characterizing the interplay between the forces at work. Similar to how icebergs actually sit in water, buoyancy often results in the broad-side of the object laying perpendicularly to the force of gravity. Though if the object moves through a fluid, the force of drag often causes the object’s broadside to become parallel to its direction of motion. This leads to a dynamic and changing net force that causes spheroids to tumble, flutter, or in some instances, rise in a helical trajectory like a surfacing submarine. By coloring sections of the spheroid particles in their experiment and tracking their motion in 3-dimensions, the researchers were able to fully reconstruct the motion of their particles including more subtle fluctuations in the orientation of these particles.
The authors found these dynamics to be predictable based on how non-spherical the particles were, classifying their motion into several broad categories. In particular, they tracked a range of particles, from oblate (shaped like an M&M) to prolate (shaped like a drug capsule). Generally, oblate particles were more likely to flutter – like the wobbling of a spinning coin as it comes to rest – while prolate particles could be found to rise in a helical trajectory.
Perhaps surprisingly, despite rising and falling particles appearing similar, their dynamics in general, are not. For a particle to rise, its density must be lower than the fluid it’s in. But increasing the particle’s density does more than cause it to sink. It can also limit the particle’s ability to take on some of the more dramatic fluttering and wobbling motions. And while this study broadly classifies a range of rise behaviors, the researchers note there are still outstanding questions about how the frequency with which the particles deviate from their purely vertical rise (zig-zagging for instance) is still somewhat mysterious.
Like many classic problems, the seeming simplicity in fact belies a host of rich and complicated behaviors. Yet this study presents a big step in characterizing and understanding processes like mechanical mixing in microfluidic devices, settling of sediment, or even the vertical rise of aquatic gastropods. However, it would seem that a full description of this common phenomenon may never truly be “simple”.