Alban Sauret

We highlight some DIW challenges related to fluid mechanics and soft matter, such as extrudability and clogging, filament stability, post-deposition spreading, slumping, and buckling. Hopefully, it will inspire various fundamental studies in fluid mechanics. (including by us)

Thrilled that our article in @annualreviews.bsky.social
of Fluid Mechanics is out! “Fluid Mechanics Challenges in Direct‑Ink‑Writing Additive Manufacturing” doi.org/10.1146/annu.... I am grateful to the two co-authors, @raytyler.bsky.social and Brett Compton. @univofmaryland.bsky.social

New @univofmaryland.bsky.social article about our NSF project on sediment flows with Eckart Meiburg @ucsbengineering.bsky.social me.umd.edu/news/story/s.... Thrilled to see the project featured and excited to get started.

Take‑home. Very small holes clog; below ~3 grain diameters there’s no flow, and around 3–6 it’s intermittent. Large holes act like dense, fluid‑like jets with a steady rate. This is also why hourglasses keep time so well. @univofmaryland.bsky.social @ucsbengineering.bsky.social [4/4]

Why openings matter. Near the edge, grains dilate in a thin boundary layer. This boundary layer only extends 10–15 grain diameters, but it changes the discharge rate. Once you account for it, all the data collapse onto a single curve! [3/4]

What we find. We split the flow rate in two: the speed of the grains and how they pack at the opening. Gravity and the hole size set the speed. Away from the rim, packing settles to a near‑universal “free‑fall” value. We show this with 3D experiments and DEM simulations. [2/4]

Excited to share our new preprint on the discharge of granular materials from a silo. Led by @ramsudhirsharma.bsky.social , we went after a simple question: What is the flow rate through the opening? The answer turns out to be "simple" and quite general. See more here: arxiv.org/abs/2509.14415 [1/4]

NSF Graduate Research Fellowship Program (GRFP)

The GRFP lives!! (due end of October)
www.nsf.gov/funding/oppo...

Excited to share that our NSF PMP project with Eckart Meiburg has been funded! We’ll study cohesive immersed granular flows through experiments and simulations to improve predictions of sediment transport & slurry processing. @univofmaryland.bsky.social @ucsbengineering.bsky.social

Check out the @kitp-ucsb.bsky.social conference we're (Vashan Wright, Sujit Datta, Nathalie Vriend) organizing:
www.kitp.ucsb.edu/activities/s... for THIS JANUARY 6-9!
Geoscientists, physicists and engineers: are you intellectually adventurous and been wondering "is this all there is?" 🧪

Our new study from Joanne Steiner’s PhD work and with C. Morize, P. Gondret, and I. Delbende has just been published in Phys. Rev. Fluids! We study vortex rings generated when a disk moves toward or away from a wall. doi.org/10.1103/ynxr...

Excited to be an invited speaker in EP018: Geophysical Granular Flows & Sediment Transport at AGU 2025 (Dec 15–19)! I’ll be sharing our results on cohesive granular materials. Many thanks to the organizers!
Abstract submissions open until July 30. agu.confex.com/agu/agu25/pr... @agu.org

We are grateful to receive funding from the ACS PRF to investigate how fibers and anisotropic particles reorient, bend, and sometimes clog in porous media. From microplastic transport to fiber-laden inks, we aim to uncover the physics behind their transport through experiments and modeling.

Congrats to all the new Fellows! It’s quite an impressive cohort

On the shape of air bubbles trapped in ice | PNAS Water usually contains dissolved gases, and because freezing is a purifying process these gases must be expelled for ice to form. Bubbles appear at...

5/ Read more :

🔗 Popular science article FR : www.espci.psl.eu/fr/actualite...
🔗 Full publication in PNAS: www.pnas.org/doi/10.1073/...

YouTube video by American Physical Society V0055: Drop impact of fiber suspensions

And a video entry to the Gallery of Fluid Motion at the APS DFD 2023: www.youtube.com/watch?v=V0RJ...

And bonus: the winning entry from @ramrajesh97 to the Gallery of Soft Matter @apsdsoft.bsky.social last year that shows some cool pictures with fiber suspensions

Capillary flows of particulate suspensions are already complex, but anisotropic fibers add even more layers of complexity. We are excited to further explore fiber dynamics in various situations. Feedback and suggestions are very welcome!

#3: Fiber coverage becomes uneven when increasing the volume fraction of fibers. Increased fiber overlap at higher concentrations reduces coating uniformity, despite fibers maintaining an isotropic orientation.

#2: Higher Weber numbers and increased fiber fractions enhance splashing events. We map this splash/no-splash transition.

#1: Increasing fiber concentration significantly reduces droplet spreading due to higher effective viscosity. Our findings extend existing spreading models of suspensions of spherical particles to account for fiber suspensions explicitly.

We studied droplets of non-Brownian fiber suspensions at varying volume fractions and fiber aspect ratios. Using high-speed imaging and absorption spectroscopy, we quantified droplet spreading, film thickness, and coating uniformity.

A new article with @sreeramr.bsky.social is out in JCIS! We study the dynamics of droplets of fiber suspensions impacting surfaces, a topic important for coating processes and additive manufacturing, among others doi.org/10.1016/j.jc... @univofmaryland.bsky.social @ucsbengineering.bsky.social

Edgerton seated on the floor amidst various pieces of photo and electronics equipment. He is wearing a white shirt, diagonal striped tie, and dark pants in this black and white photo. Various strobe lights are visible, ad well as an oscilloscope. There are cables dangling from large pieces of electronics. Edgerton is not smiling; he is just looking at the camera.

A high speed photo of a bullet passing through an apple. The apple is mounted on a metal rod and the bullet has just exited the apple. There are large sprays of apple coming from the entrance and exit points. The apple is red, with a yellow patch around the stem which is pointed at the camera.

Another well-known Edgerton photo of a bullet bisecting a playing card. The card is the king of diamonds, and it has been ripped in half along its width by the bullet passing through. The king is facing the camera.

Edgertons famous photo of a splash of white liquid, probably milk, in a red bowl. The splash is shaped like a crown, with rounded blobs forming and separating at the end of the spikes. A small drop hangs in mid-air above the splash. It is not clear from the photo whether this is another drop falling down, or a small drop that was sent back upwards when the original drop hit.

Engineer and photographer Harold Edgerton was born #OTD in 1903.

He pioneered various forms of high-speed photography using specialized cameras, strobe lighting, and other techniques. You’ve probably seen many of the images he created! 🧪 ⚛️ 📸

Images: MIT; H. Edgerton

Had a great time at @upenn.edu last Tuesday giving a seminar. Great discussions and cool research all around! Thanks to everyone for the warm welcome. Looking forward to future interactions!

YouTube video by American Physical Society V0094 - Kaleidoscope of impulse waves

We hope this work advances our understanding of wave generation mechanisms, crucial for predicting natural disasters like tsunamis and glacier calving events.
You can also watch this video we previously created for the Gallery of Fluid Motion: www.youtube.com/watch?v=DuIn...

We identified diverse wave phenomena: dispersive waves, solitary waves, breaking bores, and notably, slender water jets. When piston acceleration nears gravitational acceleration, we observed a transition to water jets—beyond traditional wave-generation models.

Through lab experiments, we investigated how the sudden movement of a rigid wall (piston) creates water waves. Depending on speed, stroke, and water depth, we observed distinct wave regimes.

Nascent water waves induced by the impulsive motion of a solid wall | Journal of Fluid Mechanics | Cambridge Core Nascent water waves induced by the impulsive motion of a solid wall - Volume 1008

Our new study, led by Philippe Gondret and Cyprien Morize (FAST Laboratory), part of Wladimir Sarlin's PhD, has just been published in Journal of Fluid Mechanics. It explores how impulsive motions generate waves. doi.org/10.1017/jfm.... @univparissaclay.bsky.social @univofmaryland.bsky.social

Sand is far more fascinating up close! Each grain is unique, with its own signature of geological history and micro-shape sculpted by time and erosion. Yet, collectively, they can behave as a fluid! magnifiedsand.com has a lot of cool pictures from all around the world!