Duarte Rocha
duarterocha17.bsky.social
Duarte Rocha
@duarterocha17.bsky.social
Reposted by Duarte Rocha
📢 Checkout our work in J. Fluid Mech. (bit.ly/3QuxMgE) on how viscosity alters drop-impact forces. Together with Bin Zhang, Cunjing Lv, & Detlef Lohse. The first and second force peaks emerge from distinct flow mechanisms—one at impact, another at take-off. @poftwente.bsky.social bit.ly/4gUvD8P
[SM1]: The role of viscosity on drop impact forces
The case shown here is We = 40, Oh = 0.0025. Paper: https://doi.org/10.48550/arXiv.2311.03012 Full description: Comparison of the drop impact force $F(t)$ obtained from experiments and simulations for the three typical cases with impact velocity $V_0 = 1.2\,\si{\meter}/\si{\second}, 0.97\,\si{\meter}/\si{\second}, 0.96\,\si{\meter}/\si{\second}$, diameter $D_0 = 2.05\,\si{\milli\meter}, 2.52\,\si{\milli\meter}, 2.54\,\si{\milli\meter}$, surface tension $\gamma = 72\,\si{\milli\newton}/\si{\meter}, 61\,\si{\milli\newton}/\si{\meter}, 61\,\si{\milli\newton}/\si{\meter}$ and viscosity $\eta_d = 1\,\si{\milli\pascal\second}, 25.3\,\si{\milli\pascal\second}, 80.2\,\si{\milli\pascal\second}$. These parameter give $Oh = 0.0025, 0.06, 0.2$ and $We = 40$. For the three cases, the two peak amplitudes, $F_1/(\rho_dV_0^2D_0^2) \approx$ 0.82, 0.92, 0.99 at $t_1 \approx 0.03\sqrt{\rho_dD_0^3/\gamma}$ and $F_2/(\rho_dV_0^2D_0^2) \approx$ 0.37, 0.337, 0.1 at $t_2 \approx 0.42\sqrt{\rho_dD_0^3/\gamma}$, characterize the inertial shock from impact and the Worthington jet before takeoff, respectively. The drop reaches the maximum spreading at $t_{\text{max}}$ when it momentarily stops and retracts until $0.8\sqrt{\rho_dD_0^3/\gamma}$ when the drop takes off ($F = 0$). The black and gray dashed lines in panel (a) mark $F = 0$ and the resolution $F = 0.5\,\si{\milli\newton}$ of our piezoelectric force transducer, respectively. We stress the excellent agreement between experiments and simulations without any free parameters. The left part of each numerical snapshot shows (on a $\log_{10}$ scale) the dimensionless local viscous dissipation function $\tilde{\xi}_\eta \equiv \xi_\eta D_0/\left(\rho_dV_0^3\right) = 2Oh\left(\boldsymbol{\tilde{\mathcal{D}}:\tilde{\mathcal{D}}}\right)$, where $\boldsymbol{\mathcal{D}}$ is the symmetric part of the velocity gradient tensor, and the right part the velocity field magnitude normalized with the impact velocity.
bit.ly
February 22, 2025 at 9:39 AM
Reposted by Duarte Rocha
Join me on Jan 30 (4 PM CST) at @UIUC for my seminar on how polymeric liquids can be the “Drosophila” of unsteady continuum mechanics—revealing how polymers reshape free-surface instabilities (drops, bubbles, jets).
Abstract: tinyurl.com/23dnlup9
Please DM or email me for details on how to join!
January 27, 2025 at 7:38 AM
Reposted by Duarte Rocha
Our Annual Review of Fluid Mechanics is now accessible for free! find out how to make a jellyfish smoothy 🪼, or how to cross a river without a bridge 🪵... thanks @annualreviews.bsky.social for make this volume open!

www.annualreviews.org/content/jour...
January 24, 2025 at 10:15 AM
Reposted by Duarte Rocha
Happy to share that our figure from the JFM article "Bursting bubble in an elastoviscoplastic medium" was chosen as the cover for Vol. 1001!
Article: doi.org/10.1017/jfm....
Cover: doi.org/10.1017/jfm....
Huge thanks to my collab: @comphy-lab.org @Mazi_Jalaal @vinuesalab.bsky.social @Outi_Tammisola!
Bursting bubble in an elastoviscoplastic medium | Journal of Fluid Mechanics | Cambridge Core
Bursting bubble in an elastoviscoplastic medium - Volume 1001
doi.org
January 6, 2025 at 6:30 PM
Reposted by Duarte Rocha
Delighted that our research on evaporating binary drops by Pim Dekker, Christian Diddens, and Detlef Lohse, studying non-monotonic surface tension and symmetry-breaking dynamics, was one of the the 2024 APS-DFD Milton van Dyke award winners.
arXiv: tinyurl.com/2c7v7lzc.
Video: tinyurl.com/2crhbjtp
Gallery of Fluid Motion
tinyurl.com
December 11, 2024 at 12:36 PM
Reposted by Duarte Rocha
Alvaro Marin at #APSDFD2024
November 24, 2024 at 6:01 PM
Reposted by Duarte Rocha
Devaraj van der Meer from @poftwente.bsky.social @utwente.bsky.social explores the impact of boiling liquids on solid surfaces. Condensing vapor can create pressures far exceeding those in water-air scenarios. Fascinating implications for industrial applications! 🌊 #FluidDynamics #Physics #APSDFD24
November 26, 2024 at 6:33 PM