Fluid dynamics

  • Article
    | Open Access

    Microswimmers can navigate porous environments, however the impact of their directed motility on their movement in fluid flow remains an open issue. The authors show that the motility of magnetotactic bacteria in flow through a porous constriction gives rise to nonlinear flow conductivity similar to electrical diodes.

    • Nicolas Waisbord
    • , Amin Dehkharghani
    •  & Jeffrey S. Guasto
  • Article
    | Open Access

    In classical wetting, the spreading of a drop on a surface is preceded by a bridge directly connecting the drop and the surface, yet it ignores the solubility of the drop phase in the medium. Here, the authors show that dissolved drop fluid from the parent drop can nucleate on the surface as islands, one of which coalesces with the parent drop to effect wetting.

    • Suraj Borkar
    •  & Arun Ramachandran
  • Article
    | Open Access

    Whereas transitions from solid- to fluid-like states in systems of active particles have received much attention, the characterization of phase transitions in active fluids with self-organized vortices so far has remained elusive. James et al. take us on a numerical tour de force from active turbulence to active vortex crystals.

    • Martin James
    • , Dominik Anton Suchla
    •  & Michael Wilczek
  • Article
    | Open Access

    Balances for nanoparticles such as resonating fluid-filled cantilevers usually probe only mass through changes in oscillation frequency. Katsikis and Collis et al. tap information from previously ignored rotational motion to simultaneously measure particle mass and volume.

    • Georgios Katsikis
    • , Jesse F. Collis
    •  & Scott R. Manalis
  • Article
    | Open Access

    Spontaneous symmetry breaking can induce instabilities in natural and engineered systems. Nicolaou et al. show that such instabilities can be prevented by introducing suitable system asymmetry in the form of spatial heterogeneity, relevant for the development of novel control and design techniques.

    • Zachary G. Nicolaou
    • , Daniel J. Case
    •  & Adilson E. Motter
  • Article
    | Open Access

    Estimating velocities in gas liquid flows is of importance in many engineering applications. Hohermuth et al. show that previous bubble velocities obtained from intrusive probes have been underestimated and provide a correction scheme for more accurate velocity measurements.

    • B. Hohermuth
    • , M. Kramer
    •  & D. Valero
  • Article
    | Open Access

    Reactions at the interface between mineral surfaces and flowing liquids are ubiquitous in nature. Here the authors explore, using surface-specific sum frequency generation spectroscopy and numeric calculations, how the liquid flow affects the charging and dissolution rates leading to flow-dependent charge gradients along the surface.

    • Patrick Ober
    • , Willem Q. Boon
    •  & Mischa Bonn
  • Article
    | Open Access

    Reinbold et al. propose a physics-informed data-driven approach that successfully discovers a dynamical model using high-dimensional, noisy and incomplete experimental data describing a weakly turbulent fluid flow. This approach is relevant to other non-equilibrium spatially-extended systems.

    • Patrick A. K. Reinbold
    • , Logan M. Kageorge
    •  & Roman O. Grigoriev
  • Article
    | Open Access

    The dynamics of droplet impact and splash is important in many applications, yet its analysis involves difficult intertwined aspects. Here Liu et al. make shape parametrically accessible to experiment, with ferrofluidic drops passing a magnetic field in a defined way.

    • Qingzhe Liu
    • , Jack Hau Yung Lo
    •  & Lei Xu
  • Article
    | Open Access

    Nguyen et al. take a fresh look at Tesla’s concept of an asymmetric fluidic conduit. They show that for alternating flow at high frequencies the device can almost be operated as a diode, enabled by a transition to turbulent-like flow at rather low Reynolds numbers.

    • Quynh M. Nguyen
    • , Joanna Abouezzi
    •  & Leif Ristroph
  • Article
    | Open Access

    Turbulence effects explored use macroscale systems in general. Here the authors generate a turbulent plasma using laser irradiation of a solid target and study the dynamics of the plasma flow at the micron-scale by using scattering of an XFEL beam.

    • G. Rigon
    • , B. Albertazzi
    •  & M. Koenig
  • Article
    | Open Access

    A novel model for submarine tephra dispersal by hydrothermal megaplumes is proposed. The energy flux inferred from our model aligns with megaplume observations, and suggests that the catastrophic release of hot crustal fluids, as opposed to lava heating, is responsible for megaplume generation.

    • Samuel S. Pegler
    •  & David J. Ferguson
  • Article
    | Open Access

    The authors describe a dynamic surface instability between impacting materials, showing that a region of mixing grows between two media. The study implies that this can explain mixed compositions and textures in certain meteorites.

    • Avi Ravid
    • , Robert I. Citron
    •  & Raymond Jeanloz
  • Article
    | Open Access

    Methane is abundant in the Universe, is an important energy carrier and a model system for fundamental studies. Here, the authors measure the self-diffusion coefficient of supercritical methane at ambient temperature up to the freezing pressure, and find a different behavior than expected based on previous models.

    • Umbertoluca Ranieri
    • , Stefan Klotz
    •  & Livia E. Bove
  • Article
    | Open Access

    Fick’s laws describe the essential physics of diffusion, but it is challenging to extend them to systems out of equilibrium. The authors derive the diffusivity of particles near active carpets - a surface covered with hydrodynamic actuators, which provides a framework for transport in living matter.

    • Francisca Guzmán-Lastra
    • , Hartmut Löwen
    •  & Arnold J. T. M. Mathijssen
  • Article
    | Open Access

    Gymnosperm sapwood is an abundantly available material to construct water filters but the material’s behaviour as a filter is poorly understood and challenges such as short shelf live have not been addressed. Here, the authors develop guidelines for the design and fabrication of xylem filters and demonstrate gravity-operated filters with a shelf life of more than two years for the removal of contaminants from spring, tap and ground water.

    • Krithika Ramchander
    • , Megha Hegde
    •  & Rohit Karnik
  • Article
    | Open Access

    The classic Leidenfrost phenomenon is familiar, yet its physics is rather complex. Graeber et al. observe the unexpected development of repeated hopping of a droplet trampolining on its own vapor cushion on a hot plate and show under which conditions this self-initiated motion occurs.

    • Gustav Graeber
    • , Kartik Regulagadda
    •  & Dimos Poulikakos
  • Article
    | Open Access

    This study investigates the underlying physical mechanisms of turbidity currents travelling thousands of miles in confined submarine settings, rather than diffusing after short distance. Using high resolution simulations with up to a billion grid points helps to understand the evolving layered structure of a current.

    • Jorge S. Salinas
    • , S. Balachandar
    •  & M. I. Cantero
  • Article
    | Open Access

    Nanofluidic channels offer the possibility to process small molecules or colloids, but transport control meets serious challenges. Seo et al. use evaporation-driven advective flow to establish a versatile manipulation scheme of the fluid carrier, disposing of external connectors.

    • Sangjin Seo
    • , Dogyeong Ha
    •  & Taesung Kim
  • Article
    | Open Access

    Sniff frequency naturally varies with animal type due to allometric scaling. Using data from live animals and a machine olfactory system, Spencer et al. reveal a deeper reason for sniffing with implications for designing gas detectors: the sniff is adapted to efficient odor detection.

    • Thomas L. Spencer
    • , Adams Clark
    •  & David L. Hu
  • Article
    | Open Access

    There is a renewed interest in Faraday waves patterns in the field of nonlinear metamaterials due to their tunable templating capacity. Kharbedia et al. show that free-standing water surfaces with ordered patterns can be generated and controlled by the Faraday waves with help of stiffening surfactants.

    • Mikheil Kharbedia
    • , Niccolò Caselli
    •  & Francisco Monroy
  • Article
    | Open Access

    A self-propelling agent at small Reynolds numbers usually requires a fore-aft asymmetry in order to circumvent the scallop theorem. Here Rogowski et al. show that this need not be true for motion in non-linear viscoelastic fluids, where an initial symmetry may be broken spontaneously.

    • Louis William Rogowski
    • , Jamel Ali
    •  & Min Jun Kim
  • Article
    | Open Access

    Melting and crystallization of ice close to the triple point is mediated by a thin liquid layer of water. Within an extended theoretical-numerical model, Sibley et al. capture both equilibrium properties and kinetic aspects of the film evolution to arrive at a broader perspective of how ice grows.

    • David N. Sibley
    • , Pablo Llombart
    •  & Luis G. MacDowell
  • Article
    | Open Access

    Solid-state nanopores can serve as single molecule sensors for DNA sequencing, but the current designs suffer from fast DNA translocation so low detectivity. Wang et al. slow down and control the translocation speed by 5 orders of magnitude using a leakage field generated at the nanopore tip.

    • Ceming Wang
    • , Sebastian Sensale
    •  & Hsueh-Chia Chang
  • Article
    | Open Access

    Multi-emulsion droplets may lead to improved designs of soft materials or drug formulations. Tiribocchi et al. show that in typical situations expected during microfluidic post-processing, the dynamical distribution of emulsified droplets is dictated by the internal vortices of the host droplet.

    • A. Tiribocchi
    • , A. Montessori
    •  & D. A. Weitz
  • Article
    | Open Access

    Whether a turbulent flow would inevitably develop singular behavior at the smallest length scales is an ongoing intriguing debate. Using large-scale numerical simulations, Buaria et al. find an unexpected non-linear mechanism which counteracts local vorticity growth instead of enabling it.

    • Dhawal Buaria
    • , Alain Pumir
    •  & Eberhard Bodenschatz
  • Article
    | Open Access

    The robust production of droplets by microfluidic T-junctions is a well-established technique. Um et al. demonstrate how the mutual interaction between droplets can be used to achieve additional control including the simultaneous release of droplets caused by synchronization phenomena.

    • Eujin Um
    • , Minjun Kim
    •  & Joonwoo Jeong
  • Article
    | Open Access

    In some materials electrons can behave hydrodynamically, exhibiting phenomena associated with classical viscous fluids. In this theory work, the authors show that the symmetries of the crystal lattices in which the electrons reside can lead to additional unique hydrodynamic effects.

    • Georgios Varnavides
    • , Adam S. Jermyn
    •  & Prineha Narang
  • Article
    | Open Access

    Extreme events high up in the winter stratosphere are known to influence our weather and their predictability has potential to improve seasonal weather forecasts. Here, the authors examine factors that influence their generation and highlight a previously unrecognised sensitivity to the upper equatorial stratosphere.

    • L. J. Gray
    • , M. J. Brown
    •  & J. Anstey
  • Article
    | Open Access

    The authors introduce a dynamic spatial ultrasound modulator, based on digitally generated patterns of microbubbles controlled by a complementary metal–oxide–semiconductor (CMOS) chip. They achieve reshaping of incident plane waves into complex acoustic images and demonstrate dynamic parallel assembly of microparticles.

    • Zhichao Ma
    • , Kai Melde
    •  & Peer Fischer
  • Article
    | Open Access

    Electric field induced convective instabilities in liquid crystal slabs can assume a localized shape. The authors show how to generate, manipulate and shepard these dissipative solitary excitations that do not require topological constraints for stabilization.

    • Satoshi Aya
    •  & Fumito Araoka
  • Article
    | Open Access

    In spin hydrodynamic generation originating from the coupling of mechanical rotation in a fluid and electron spin, fluid vorticity can be converted into an electric voltage via a spin current. Here, the authors demonstrate experimentally that the energy conversion in a laminar flow regime is strongly enhanced over the turbulent regime.

    • R. Takahashi
    • , H. Chudo
    •  & E. Saitoh
  • Article
    | Open Access

    Synthetic hair-like structures (cilia) controlled by an external field have been developed, especially for microfluidic applications. Here, Gu et al. make soft artificial cilia carpets with programmable magnetization patterns and utilize them to achieve pumping and locomotion in a soft robotic model.

    • Hongri Gu
    • , Quentin Boehler
    •  & Bradley J. Nelson
  • Article
    | Open Access

    Every year, hundreds of people die at sea because of vessel accidents, and a key challenge in reducing these fatalities is to make Search and Rescue (SAR) planning more efficient. Here, the authors uncover hidden flow features that attract floating objects, providing specific information for optimal SAR planning.

    • Mattia Serra
    • , Pratik Sathe
    •  & George Haller
  • Article
    | Open Access

    Current theories predict that a plate-like particle rotates continuously in a shear flow. Kamal et al. instead show that even nanometric hydrodynamic slip may induce a thin plate-like particle to adopt a stable orientation, and discuss implications of this effect for flow processing of 2D nanomaterials.

    • Catherine Kamal
    • , Simon Gravelle
    •  & Lorenzo Botto
  • Article
    | Open Access

    Most biological and artificial self-propelled particles tend to be attracted by solid walls on their swimming pathways. Vizsnyiczai et al. show that, unexpectedly, confining E. coli cells inside a channel triggers stable locomotion along the channel axis once the channel is narrower than a critical value.

    • Gaszton Vizsnyiczai
    • , Giacomo Frangipane
    •  & Roberto Di Leonardo
  • Article
    | Open Access

    High-throughput rheological measurements of cells and cell clusters by microfluidics is limited by fixed channel dimensions. Here the authors create virtual fluidic channels inside the cuvette of commercial flow cytometers to dynamically tune channel cross section to enable rheological measurements from cells and cell clusters.

    • Muzaffar H. Panhwar
    • , Fabian Czerwinski
    •  & Oliver Otto
  • Article
    | Open Access

    Dimensions and the surface properties of the nanochannels are vital to the functions and applications of nano-fluidic devices. Here Ma et al. studied the film thickness of a Bretherton bubble in a microcapillary and demonstrate the liquid film can be used for label-free biosensing.

    • Yu Ma
    • , Miao Sun
    •  & Yanbo Xie
  • Article
    | Open Access

    Here, the authors observe that laser illumination allows to displace a vial of nanoparticle solution over centimetre-scale distances. In order to explain this, they describe a novel mechanism for laser propulsion of a macroscopic object, based on light-induced thermophoresis.

    • Nikita Kavokine
    • , Shuangyang Zou
    •  & Lydéric Bocquet
  • Article
    | Open Access

    It is interesting phenomenon that chiral order can emerge in intrinsically achiral liquid crystals. Here Čopar et al. demonstrate achiral-to-chiral transition of the nematic liquid crystals flow in microfluidic channels and their behaviour, stability, and dependence on geometric and material parameters.

    • Simon Čopar
    • , Žiga Kos
    •  & Uroš Tkalec
  • Article
    | Open Access

    Aggregation of matter, common in stratified fluid systems, is essential to the carbon cycle and ocean ecology. Although the current understanding of aggregation involves only collision and adhesion, here Camassa et al. reveal a self-assembly phenomenon arising solely from diffusion-induced flows.

    • Roberto Camassa
    • , Daniel M. Harris
    •  & Richard M. McLaughlin
  • Article
    | Open Access

    It remains peculiar how to generate macroscopic work by harnessing the microscopic activity of living or synthetic agents like bacteria or micro-robots. Vincenti et al. show a biological rotary motor by self-assembling magnetotactic bacteria inside a droplet, producing a net torque on the droplet surface.

    • Benoit Vincenti
    • , Gabriel Ramos
    •  & Eric Clement
  • Article
    | Open Access

    It has been shown previously that substrate viscoelasticity affects surface wettability. Here the authors observe a wetting transition during drying of droplets on such substrates and elucidate it with high resolution force field measurements thereby determining its dependence on substrate properties.

    • Julia Gerber
    • , Tobias Lendenmann
    •  & Dimos Poulikakos