Physical Review Fluids
Author(s): G. Licsandru and M. Prat
Evaporation – condensation effects in a porous medium containing saline water enhance water transport and explain salt crust faster upward displacement.
[Phys. Rev. Fluids 7, 064304] Published Thu Jun 09, 2022
Author(s): Alireza Hooshanginejad, Sunghwan Jung, Ellen Longmire, and Sungyon Lee
In this study, we experimentally reveal the liquid-like and solid-like behaviors of millimetric liquid marbles when they sediment in oil towards a water layer below. Upon dynamically interacting with the oil-water interface, an aqueous armored droplet is shown to either rupture or remain intact as the oil surrounding the drop pinches off. The pinch-off in the novel gravity-driven regime leads to the double-encapsulation of aqueous solutions, which enables their secure transport in a wet environment. We also present scaling laws that account for the drop’s weight and the oil viscosities, in good agreement with the experiments.
[Phys. Rev. Fluids 7, 064003] Published Wed Jun 08, 2022
Author(s): Sajjad ur Rehman, Junghoon Lee, and Changhoon Lee
By adopting the direct force formulation in a finitely extensible nonlinear elastic (FENE) model for the feedback force by laden polymers to stationary isotropic turbulence, we clearly identified the energy flow between turbulence and polymers. The stretching motion of turbulence is suppressed by the polymer springs with large Weissenberg number, resulting in suppression of turbulent kinetic energy and energy dissipation.The direct force model seems to be more efficient in providing physical insight than the polymer stress model based on the conformation tensor.
[Phys. Rev. Fluids 7, 064303] Published Wed Jun 08, 2022
Author(s): Gunnar G. Peng, Callum Cuttle, Finn Box, Jian Hui Guan, Anne Juel, Christopher W. MacMinn, and Draga Pihler-Puzović
We study viscous fingering instability in a soft Hele-Shaw cell, in which one of the walls is replaced by a bounded elastomer. For sufficiently high flow rates in our experiments, fingers can get trapped because the deforming solid contacts the opposite wall, sealing the cell near its rim, although in numerical simulations of axisymmetric bubble expansion at the same control parameters, the interface escapes. For parameter regimes in which narrower fingers grow, we find the opposite behavior: the cell seals in axisymmetric numerics but fingers escape the cell in experiments, suggesting that viscous fingering can either promote or suppress the choking of the cell.
[Phys. Rev. Fluids 7, L062001] Published Wed Jun 08, 2022
Author(s): P. Hayoun, A. Letailleur, J. Teisseire, F. Lequeux, E. Verneuil, and E. Barthel
The stability of a dynamic meniscus depends upon its macroscopic curvature. In particular, the critical velocity for the dynamic wetting transition is affected by the meniscus curvature which, as such, emerges as a thickness selection mechanism for liquid film deposition. These ideas have been demonstrated experimentally by flowing water in tubes at high velocities and rationalized by numerical modeling.
[Phys. Rev. Fluids 7, 064002] Published Tue Jun 07, 2022
Author(s): Abhishek K. Singh, Rajiv K. Srivastava, and Supreet Singh Bahga
Electrohydrodynamic (EHD) jet printing is an additive manufacturing technique in which an electrified jet of functional ink is deposited on a motion-controlled substrate. Through experimental visualization of EHD jets, current measurements and scaling analysis, we show that steady EHD jetting can occur in three regimes: the cone-jet, moderately stretched jet, and thick-jet regimes. These EHD jetting regimes differ with respect to the relative importance of surface convection and bulk conduction currents downstream of the jet.
[Phys. Rev. Fluids 7, 063701] Published Mon Jun 06, 2022
Author(s): Yuta Asano, Hiroshi Watanabe, and Hiroshi Noguchi
With molecular dynamics simulations (MDS) we explore the effects of the liquid-to-vapor transition on sound waves including observation of bubble dynamics due to Bjerknes forces on a molecular scale. The usefulness of MDS for the phase transition, bubble growth, and bubble-sound interaction is demonstrated without the use of any phenomenological models.
[Phys. Rev. Fluids 7, 064302] Published Mon Jun 06, 2022
Author(s): Joel W. Newbolt, Jun Zhang, and Leif Ristroph
A swimming fish leaves behind an orderly pattern of vortices, but schools of fish are not ordered into lattice arrangements. Our experiments on robotic hydrofoils show how flapping swimmers can benefit from hydrodynamic interactions and stay in a school even without specific positioning relative to neighbors.
[Phys. Rev. Fluids 7, L061101] Published Mon Jun 06, 2022
Author(s): R. H. Allaire, L. J. Cummings, and L. Kondic
We use an asymptotic model to study instabilities of free surface films of nanometric thickness on thermally conductive substrates in two and three spatial dimensions. The film evolution is simulated using efficient GPU-based simulations which, when combined with the developed asymptotic model, allow for fully nonlinear time-dependent simulations in large three-dimensional computational domains. We find that the properties of the thermally conductive substrate - in particular its thickness and rate of heat loss - play a critical role in controlling the film temperature and dynamics. The graphic shows the influence of substrate thickness (Hs) on film temperature and breakup.
[Phys. Rev. Fluids 7, 064001] Published Thu Jun 02, 2022
Author(s): Sooyoung Chang, Kaare H. Jensen, and Wonjung Kim
Capillary flow through hydrogel-coated capillary tubes was investigated experimentally and theoretically. The results show how the absorption and swelling of hydrogel regulate capillary flow. Water imbibition through porous hydrogel materials can be understood as analogous to flow through a channel that deforms with water absorption. Therefore, this study provides a better understanding of water absorption through porous hydrogel materials, which are widely used for agricultural substrates, hygienic products, and microfluidic devices.
[Phys. Rev. Fluids 7, 064301] Published Wed Jun 01, 2022
Author(s): Lin Feng, Xin-Yao He, Ji-Long Zhu, and Wan-Yuan Shi
Magnetic manipulation of a deionized (DI) water droplet on a slippery liquid-infused porous surface (SLIPS) is realized by a single magnet. The ultra-low friction nature of SLIPS enables a small magnetic reprelling force to actuate the droplet forward successfully at a velocity of 1 mm/s. In addition, this method exhibits great potential for transporting low-surface-tension fluids such as sodium dodecyl sulfate (SDS) droplets, bubbles, and magnetic nanofluids, which offer potential benefits for the design and applications of magnetically actuated droplets in droplet microfluidics.
[Phys. Rev. Fluids 7, 053602] Published Tue May 31, 2022
Effect of streak employing control of oblique-breakdown in a supersonic boundary layer with weak wall heating/cooling
Author(s): M. Celep, A. Hadjadj, M. S. Shadloo, S. Sharma, M. Yildiz, and M. J. Kloker
High skin friction and thermal loads are inevitable consequences of turbulent flows in supersonic flights. Here, the use of boundary-layer streaks is studied by direct numerical simulations in order to prevent/delay turbulence from occuring at M_∞=2.0. The stabilizing/destabilizing effects (y/δ_in=0.517 in the image) of the streaks under the influence of various thermal boundary conditions are examined and the effective amplitude range in delaying transition is revealed.
[Phys. Rev. Fluids 7, 053904] Published Tue May 31, 2022
Author(s): Yanchen Wu, Fei Wang, Weidong Huang, Michael Selzer, and Britta Nestler
The capability of droplet absorption into a funnel-like capillary tube is enormously affected by the combined influence of the droplet size, the opening angle, and the intrinsic wettability. Through a quantitative investigation of the penetration criteria, we demonstrate that a finite-volume droplet can be totally absorbed by a hydrophobic funnel-like structure depending on the opening angle. This result is sharply contrary to the previous conclusion for infinite-volume droplets in straight capillary tubes and our predictions extend the limit of the maximum contact angle for the complete penetration of droplets into capillary tubes in the literature.
[Phys. Rev. Fluids 7, 054004] Published Tue May 31, 2022
Author(s): Daniel T. Paterson, Tom S. Eaves, Duncan R. Hewitt, Neil J. Balmforth, and D. Mark Martinez
We explore a model for compaction of a two-phase medium in which the solid is allowed to deform elasto-viscoplastically. Previous models for compression of colloidal and cellulose fiber suspensions often prescribe the solid stress as a material function of the local solid concentration. Our current model distinguishes between purely elastic or plastic deformation and allows a solid viscous response. This is crucial for model comparison to experiment where a dramatic improvement over inelastic constitutive models is demonstrated.
[Phys. Rev. Fluids 7, 054303] Published Tue May 31, 2022
Author(s): Joshua Strader, Neil Causley, Joshua A. Dijksman, and Abram H. Clark
Intrusion into fluid-grain mixtures can lead to very large stresses and surprising solid-like behavior. One important mechanism, captured by Darcy-Reynolds theory, involves a feedback effect between the expansion of the granular material (Reynolds dilation) and the flow of fluid through the pores between grains (Darcy flow). We build on prior work to demonstrate the effectiveness of Darcy-Reynolds theory in capturing the forces over a wide range of physical parameters. We also demonstrate a breakdown of the theoretical predictions for very large viscosity fluids, and we suggest a hypothesis for this deviation.
[Phys. Rev. Fluids 7, 054304] Published Tue May 31, 2022
Hierarchical clustering method of volumetric vortical regions with application to the late stage of laminar-turbulent transition
Author(s): Kazuo Matsuura and Yasuhide Fukumoto
This paper proposes a hierarchical clustering method which can analyze the behavior of vortices in detail by dividing volumetric vortical regions obtained by a direct numerical simulation into individual groups of vortical points and automatically tracking them. In addition to visualizing and tracking the instantaneous spatial distribution and temporal motion of each point set of vortices linked by a data hierarchy (inclusivity), which is called “p-clusters” in a unified manner, it is now possible to mechanically search for common local dynamics among many different vortical structures found in transitional and turbulent flows.
[Phys. Rev. Fluids 7, 054703] Published Tue May 31, 2022
Author(s): Alexander Petroff, Alejandra Rosselli-Calderon, Ben Roque, and Pradeep Kumar
Multicellular magnetotactic bacteria (MMB) – the only known obligately multicellular species of bacteria – use the geomagnetic field to navigate the pore space of water-saturated sediment. To investigate how MMB navigate around obstructions, we orient a magnetic field to direct thousands of MMB toward the hard surface of a microfluidic chamber. MMB in a sub-millitesla field distribute exponentially about the surface as an active gas with a penetration length λ proportional to the distance a colony swims before aligning with the applied field. At a critical magnetic field λ shrinks to the size of a single MMB colony and the active gas condenses into an active two-dimensional fluid.
[Phys. Rev. Fluids 7, 053102] Published Fri May 27, 2022
Effect of interface dynamic deformations on instabilities of buoyancy-thermocapillary convection in a two-fluid two-layer system
Author(s): Alexander Gelfgat
The effect of interfacial disturbances on instabilities of buoyant/thermocapillary convective flows in rectangular cavities is studied in a series of numerical experiments. The relation between interface deformations and the Boussinesq approximation is discussed. It is shown that including interface disturbances in the model can alter the critical temperature difference by approximately 10%, producing either a destabilizing, or a stabilizing effect.
[Phys. Rev. Fluids 7, 053503] Published Fri May 27, 2022
Author(s): Zhaohe Dai and Dominic Vella
Lubricated surfaces are formed by coating surfaces with a thin layer of oil lubricant. We consider a model problem to understand how lubricated surfaces respond to the deposition of a droplet, which induces forces on the lubricant via its Laplace pressure and the triple line (the Neumann balance). This forcing leads to the formation of a meniscus around the droplet, or ‘skirt’. We show that the properties of the skirt depends on the amount of lubricant available in the lubricant reservoir and also that the the evolution towards the equilibrium is extremely slow.
[Phys. Rev. Fluids 7, 054003] Published Fri May 27, 2022
Author(s): Abhinendra Singh, Grayson L. Jackson, Michael van der Naald, Juan J. de Pablo, and Heinrich M. Jaeger
Simulations link nanoscale particle properties to bulk rheology via microscopic stress-activated constraints. The framework shows quantitative agreement with experimental rheology data.
[Phys. Rev. Fluids 7, 054302] Published Fri May 27, 2022