Slippery surfaces have received great attention for more than a quarter-century. In particular, during the last decade, interest has increased exponentially, resulting in thousands of articles concerning three types of slippery surfaces: superhydrophobic, superoleophobic, and omniphobic. This review focuses on recent developments and significant findings in naturally inspired slippery surfaces. Superhydrophobicity

A levitated glycerol droplet supported by an acoustic standing wave, when subject to modulated field at frequency on the order of 150 Hz, behaves as a solid plate and exhibits flexural bending resonance rather than the conventional equatorial star-shape oscillations. Three oscillation modes are observed: seesaw, saddleback, and monkey saddle with the increasing energy levels. The finite element analysis

A viscosity overshoot of fibers filled in a polymer melt under a shear flow is much tougher to predict via the existing constitutive equations of suspension rheology in a viscous media, owing to the effect of fiber orientation on the viscoelastic behavior. The WMT-X (White–Metzner model eXtended by Tseng) viscoelastic fluid model coupled with the typical Dinh–Armstrong fiber suspension model, known

This Letter reports a validation of a lattice-Boltzmann approach following the Taylor–Green Vortex benchmark presented at the 19th International Congress on Numerical Combustion and recently reported by Abdelsamie et al. [“The Taylor–Green vortex as a benchmark for high-fidelity combustion simulations using low-Mach solvers,” Comput. Fluids 223, 104935 (2021)]. The lattice-Boltzmann approach, despite

We study the fully coupled dynamics between a fully developed turbulent flow and an ensemble of immersed flexible fibers. We vary the concentration of the suspension, the mechanical properties, and the length of the fibers in a vast parametric range. For all configurations, the fiber dynamics falls in only two possible dynamical states: (i) the fiber manifests its natural response to the flow forcing

An experiment is conducted in a small-scale air–water test loop to investigate the severe slug flow-induced vibration of a flexible catenary riser of aspect ratio (the riser length over its internal diameter) 200. The vibration displacement of the catenary riser as well as the internal flow features is simultaneously captured by high-speed cameras. Three stages are observed during a cycle of severe

An analytic model for steady state turbulence is employed to obtain the inertial range power spectrum of compressible turbulence. We assume that for homogeneous turbulence, the timescales controlling the energy injected at a given wavenumber from all smaller wavenumbers are equal for each spatial component. However, the longitudinal component energy is diverted into compression, so the rate controlling

Understanding the dynamics of micro-organisms will help in developing artificial swimmers for applications like drug delivery. In the present study, a two-dimensional one-hinge swimmer resembling a scallop in Newtonian fluid is explored. To model the one-hinge swimmer, we use bead-spring model and the fluid is simulated using multi-particle collision dynamics with Anderson thermostat. We consider a

By using an axisymmetric immersed-boundary model, fluid dynamics of a cephalopod-inspired propeller undergoing periodic inflation–deflation deformation in background flow is numerically studied in a low Reynolds number regime. A thrust-drag decoupling method based on physical analysis is proposed, in which the jet-related thrust is obtained as the summation of three parts: the jet momentum flux, the

The swimming ability of fish is greatly influenced by the hydrodynamics of their caudal fins. In this paper, the effects of flexibility and shape on the performance of a bioinspired panel are numerically studied. The flexibility is simplified as a torsional spring, and three typical shapes (i.e., square, convex, and concave shapes) are considered. The results are obtained based on three-dimensional

Bifurcating vessel is a characteristic feature of biological systems such as arteries in the cardiovascular system and pulmonary airways. In cardiovascular system, the bifurcations are often asymmetric, flow is pulsatile, and the fluid, blood, shows a complex rheology. In this work, we study computationally pulsatile flow in planar symmetric and asymmetric, three-dimensional bifurcating vessels. The

Near-wall blood flow and wall shear stress (WSS) regulate major forms of cardiovascular disease, yet they are challenging to quantify with high fidelity. Patient-specific computational and experimental measurement of WSS suffers from uncertainty, low resolution, and noise issues. Physics-informed neural networks (PINNs) provide a flexible deep learning framework to integrate mathematical equations

Laser-induced-forward-transfer (LIFT)-based laser assisted bioprinting (LAB) has great advantages over other three-dimensional (3D) bioprinting techniques, such as none-contact, free of clogging, high precision, and good compatibility. In a typical LIFT based LAB process, a jet flow transfers the bioink from the ribbon to the substrate due to bioink bubble generation and collapse, and the printing

The passive particle transport through narrow channels is well studied, while for an active particle system, it is not well understood. Here, we demonstrate the active control of the transport through a nanopore via mean-field analysis and molecular dynamics simulations. We prove that the active force enhances the transport efficiency with an effective diffusion coefficient D eff = D t ( 1 + P e 2

The rheological properties of cells and tissues are central to embryonic development and homeostasis in adult tissues and organs and are closely related to their physiological activities. This work presents our study of rheological experiments on cell monolayer under serum starvation compared to healthy cell monolayer with full serum. Serum starvation is one of the most widely used procedures in cell

This paper is on an implicit time integration scheme for simulation of red blood cell (RBC) flow in an ambient fluid. The intra- and extracellular plasmas are modeled as Stokes flows and represented by boundary integral equations (BIE) written in a weakly singular form. The cell membrane is modeled as a thin elastic shell. Expressed in this way, the RBC flow model constitutes an implicit ordinary differential

This paper addresses hydrodynamic performance of fins regarding their trailing edge convexity–concavity and flexibility distribution. The effects of trailing edge convexity–concavity on propulsive performance and vortex dynamics were investigated experimentally utilizing time-resolved particle image velocimetry and force sensors. It was found that the convex trailing edge shape always outperforms the

The gas–liquid interface (GLI) over superhydrophobic surfaces (SHSs), where the flow slips, is the key to reduce frictional drag in underwater applications. Many-body dissipative particle dynamics simulations are used to explore the slip behavior of a shear flow over a rectangular grooved SHS, and a flat GLI is obtained by tuning the contact angle of the GLI. Due to the slip, the normal profiles of

Nanoemulsions consist of small particle size, uniform dispersion, and long-term stability, making them suitable for use in enhanced oil recovery for low-permeability reservoirs. In this paper, an ultrastable oil-in-water nanoemulsion was prepared using the emulsification inverse phase method at a constant temperature. Rheology, multiple-light scattering, laser particle size analyzer, and optical microscope

This study proposes a scattering database method to model gas–solid interaction based on a database of distributions of scattering velocity obtained by a molecular dynamics simulation. The proposed method is used as the boundary condition in the direct simulation Monte Carlo method to simulate hypersonic flow over a rounded wedge at different Knudsen numbers (Kn). The effects of different wall models

In this paper, the lifetime of coronavirus infected droplets under a stick-slip evaporation mode has been investigated, which may play a pivotal role in reducing the spread of COVID-19 infection. It is showed that the survival time of the virus can be reduced by increasing the receding contact angle or by reducing the initial contact angle of a drop deposited on a solid surface. It has been found that

Capillary microflows of liquid crystal phases are central to material, biological and bio-inspired systems. Despite their fundamental and applied significance, a detailed understanding of the stationary behavior of nematic liquid crystals (NLC-s) in cylindrical capillaries is still lacking. Here, using numerical simulations based on the continuum theory of Leslie, Ericksen, and Parodi, we investigate

A lipid coated bubble (LCB) oscillator is a very interesting non-smooth oscillator with many important applications ranging from industry and chemistry to medicine. However, due to the complex behavior of the coating intermixed with the nonlinear behavior of the bubble itself, the dynamics of the LCB are not well understood. In this work, lipid coated Definity® microbubbles (MBs) were sonicated with

It is commonly accepted that shear waves do not propagate in a liquid medium. The shear wave energy is supposed to dissipate nearly instantaneously. This statement originates from the difficulty to access “static” shear stress in macroscopic liquids. In this paper, we take a different approach. We focus on the stability of the thermal equilibrium while the liquid (glycerol) is submitted to a sudden

This paper investigates the path selection of bubbles suspended in different power-law carrier liquids in microfluidic channel networks. A finite volume-based numerical method is used to analyze the two-dimensional incompressible fluid flow in microchannels, while the volume of fluid method is used to capture the gas–liquid interface. To instill the influences of shear thinning, Newtonian, and shear-thickening

Microfluidic systems are an interesting topic for investigation due to their wide-spreading applications. Nowadays, polymeric solutions are used mainly for the generation of microparticles in biomedical engineering, food, and pharmaceutical industries. Droplet-based microfluidic devices have proposed an extensive interest in many applications such as chemical/biological/nanomaterial preparation to

Using micro-particle image velocimetry (μPIV), the convective flow inside a silicone oil droplet was investigated in detail during its formation in coaxial capillaries under co-flow in a water/glycerol mixture continuous phase. The analysis of μPIV measured flow field revealed that two characteristic flow areas exist in the droplet in formation: an inflow zone and a circulation zone. The intensity

Sheltering vortices by shear flow is a common method in plasma and neutral fluids and has recently been successfully applied to control ionic fluids. This work proposes a new chemical sheltering vortex method for electroconvective instability (ECI) based on the Onsager chemical effect. We reveal unique ECI behaviors in a weak electrolyte with the Onsager effect, including the vortex height selection

Droplets and bubbles are thought to be two sides of the same coin; this work determines how true this is at the molecular scale. Stable cylindrical nanodroplets and nanobubbles are obtained in Molecular Dynamics (MD) simulations with three-phase contact lines pinned by alternate hydrophobic and hydrophilic patterns. The surface tension and Tolman length for both types of curved interfaces are obtained

In the present paper, the effect of double diffusion natural convection fluid flow inside the double wavy enclosure using the mesh-free method is investigated. The enclosure is filled with nanofluid whose base fluid is non-Newtonian. The results are obtained for the variation in Brownian motion parameter ( 0.2 – 0.8), buoyancy ratio parameter ( 0.2 – 1), power-law index ( 0.2 – 1), thermophoresis parameter

When the density of the fluid surrounding suspended Brownian particles is appreciable, in addition to the forces appearing in the traditional Ornstein and Uhlenbeck theory of Brownian motion, additional forces emerge as the displaced fluid in the vicinity of the randomly moving Brownian particle acts back on the particle giving rise to long-range force correlations which manifest as a “long-time tail”

We study the dynamics of Newtonian fluids subject to complex pressure gradients within bent oscillating nanotubes. Pressure gradients with four different purely oscillatory time profiles are explored by theoretical means, in order to unveil the mechanism of interaction between the characteristic time of tube vibration and the multiple characteristic times involved in the complex pressure signal. We

A conceptual and mathematical framework for the singularity-free modeling of non-equilibrium solidification/melting and non-isothermal dynamic wetting is developed where both processes are embedded into a broader class of physical phenomena as particular cases. This allows one to consider problems describing fluid flows with phase transitions and dynamic wetting occurring independently or interactively

Free-surface effects induced by internal solitary waves (ISWs) propagating through a background shear current are theoretically investigated in a shallow water framework. Following the Hamiltonian approach, we implement a mathematical formulation valid for a free surface, two-layer stratified system in the presence of mobile layers. Associated to the undisturbed condition characterized by the background

Droplet impact on a spinning surface has been observed in different industries and plays an important role in the performance of industrial systems. In the current study, the dynamics of water droplet impact on a hydrophilic spinning disk is investigated. An experimental setup is designed in a way that droplet diameter, impact velocity, disk rotational speed, and location of impact are precisely controlled

Thin films can become unstable when attractive van der Waals forces overcome the stabilizing effects of surface tension and viscous forces. In many applications, the effect of the surrounding bulk fluid cannot be neglected when considering a thin film subject to perturbations. In this work, we examine the two limits of potential flow and Stokes flow in the surrounding bulks to derive dispersion relations

In this paper, a hybrid lattice-Boltzmann finite-difference method is developed for the simulation of ternary fluids near immersed solid objects of general shapes. The flow equations are solved by the lattice-Boltzmann method and the coupled Cahn–Hilliard equations for interface evolutions are solved by the finite-difference method. A special implementation of the wetting boundary condition on a surface

The thermocapillary effect, arising flow due to a temperature gradient along a fluid interface, is the dominant effect in some industrial and microfluidic processes and must be studied in order to optimize them. In this work, we analyze how insoluble surfactants adsorbed at the interface can affect such a flow. In particular, we analyze the case where the thermocapillary flow is induced at the air–water

The highest standing surface wave at infinite depth is a classical hydrodynamic problem, illuminated by Taylor's excellent experiments [G. I. Taylor, “An experimental study of standing waves,” Proc. R. Soc. London, Ser. A 218, 44–59 (1953)]. Based on length scale arguments, we present a compact analytical approach to the highest standing wave. Our physical postulate is that the highest deep-water wave

In this work, the post-impact drop motions of the rebound regime on inclined hydrophobic surfaces are investigated using a numerical technique. The effects of impact velocity ( V i = 0.5–1.5 m/s), drop diameter ( D 0 = 1.0–2.5 mm), surface wettability ( θ e q = 120°–160°), and inclined angle ( α = 0°–80°) on the post-impact regimes, contact time ( t c) and spreading time ( t s), nondimensionalized

The extended thin-film region adjacent to the contact line is crucial in heat transfer because of its capability to enhance heat transfer and its critical role in wetting dynamics. The present investigation focused on the study of advancing contact line morphology induced by water vapor condensation. The condensation was at low rates with the advancing velocities <60 nm/s. Two modes of atomic force

We consider a numerical approach for a covariant generalized Navier–Stokes equation on general surfaces and study the influence of varying Gaussian curvature on anomalous vortex-network active turbulence. This regime is characterized by self-assembly of finite-size vortices into linked chains of anti-ferromagnet order, which percolate through the entire surface. The simulation results reveal an alignment

Bouncing drops on solid surfaces have gained increasing attention for various practical applications, such as self-cleaning and anti-icing strategies. Breaking the circular symmetry in bouncing dynamics on a ridge enables drop dynamics to be modified significantly and the residence time of drops on surfaces to be reduced. Here, we numerically investigate the asymmetric bouncing dynamics of oblate and

Jet formation and break-up in inkjet printing has been studied and understood mainly for pure liquids. Questions remain as to the role of surfactants on the inkjet printing process at the microsecond timescale. Here, numerical and experimental results demonstrating the effects of surfactants on jet break-up and drop formation at the scales relevant to drop-on-demand inkjet printing are presented. The

We report the dynamics of a viscoplastic (Bingham) torus suspended in an unbounded Newtonian medium. In this study, the immiscible ambient fluid is subjected to an axisymmetric compressional (biaxial-extensional) flow. Numerical simulations applying the boundary integral formulation to the Stokes flow are performed for the torus drop having initially a circular cross section. The quasi-stationary dynamic

The rheological behavior of an emulsion is determined by microstructural changes caused by external loads. Some of these changes are irreversible due to the occurrence of the destabilization processes. Therefore, a deeper understanding of the system may be acquired by linking rheological characterization results with microscopic events. It is important to understand the rheological consequences of

Bulk viscosity describes the irreversible resistance to the rate of volume change. Bulk viscosity, which is more than ten thousand times higher than shear viscosity, has been ignored in the field of polymer processing for the past decades. Bulk viscosity may play an important role for compressible polymer melts undergoing strong compression during processing, especially during the packing and holding

In the present paper, a numerical investigation was performed to assess the effect of the rheological behavior of non-Newtonian fluids on Rayleigh–Bénard thermosolutal convection instabilities within shallow and finite aspect ratio enclosures. Neumann and Dirichlet thermal and solutal boundary condition types were applied on the horizontal walls of the enclosure. Using the Boussinesq approximation

Professor R. Byron Bird used Oldroyd models of rheological behavior over a span of around 50 years. In this paper, it is suggested that a modified Oldroyd-B model can also be used to describe the rheology of non-colloidal suspensions that have a viscoelastic matrix.

We provide the first direct calculation of the Knudsen layer (KL) thickness in rarefied gas flows based on the ballistic molecular motions in the direct simulation Monte Carlo simulations. Calculations reproduce a linear relation between the KL thickness and the mean free path (MFP) of the gas, which agrees with the classical gas kinetic theory statement. The ratio of the KL thickness and MFP is only

Bubble trajectories in the presence of a decaying Lamb–Oseen vortex are calculated using a modified Maxey–Riley equation. Some bubbles are shown to get trapped within the vortex in quasi-equilibrium states. All the trapped bubbles exit the vortex at a time that is only a function of the Galilei number and the vortex Reynolds number. The set of initial bubble locations that lead to entrapment is numerically

We study numerically the dynamics of an air-in-liquid compound drop impacting onto a solid surface. We demonstrate that the addition of a bubble in the drop decreases its maximum spreading. This decrease is explained by the lower kinetic energy of the drop, but also amplified by the formation of a vertical jet emerging from its center, and a relative increase in the viscous dissipation. We propose

The vortex-induced vibration and solid-structure impact of a neutrally buoyant horizontal flexible pipe in the vicinity of a bottom wall boundary are experimentally investigated in a water flume. The pipe with an aspect ratio of 87 is arranged with an oblique angle of 30° and an initial gap-to-diameter ratio of 0.5. A non-intrusive measurement with two high-speed cameras is employed to simultaneously

This experimental study reveals a counterflow slip at the interface of two immiscible fluids filling a sealed vertical cylindrical container whose bottom disk rotates while other walls are stationary. An advanced particle image velocimetry helps us analyze and quantify streamline patterns and velocity profiles of the steady axisymmetric flows of both fluids. As the angular velocity of a disk increases

This is a companion paper to a previous study of hypersonic boundary layer transition over a concave wall [Huang et al., “Inner structures of Görtler streaks,” Phys. Fluids 33, 034116 (2021)]. Experiments are performed in a Mach 6.5 quiet wind tunnel using CO2-enhanced filtered Rayleigh scattering flow visualization, PCB fast-response pressure sensors, and a high-frequency Schlieren technique to investigate

A new physical effect, consisting in the crossover of values and inversion of the dynamic contact angles' hysteresis branches, when a glycerin drop and a water drop slide up a smooth inclined steel plane under the action of nanosecond spark discharges' periodic sequence, was experimentally recorded.

This study explores the nature of forces developed by a batoid-inspired undulating circular planform. The forces that arise from this type of fin-based propulsion have two components, one due to added mass effects and a second one due to circulation. The present work studies the impact of specific fin kinematic parameters on the individual contributions of these components. Numerical simulations are

A new approach to studying active suspensions is presented. They exhibit a specific behavior pattern, sometimes referred to as active turbulence. Starting from first principles, we establish a description for an active suspension, consisting of a Newtonian fluid and active Janus particles. The fluid phase is described by Navier–Stokes equations and the particles by Newton–Euler equations. A level set

The recent outbreak of the SARS CoV-2 virus has had a significant effect on human respiratory health around the world. The contagious disease infected a large proportion of the world population, resulting in long-term health issues and an excessive mortality rate. The SARS CoV-2 virus can spread as small aerosols and enters the respiratory systems through the oral (nose or mouth) airway. The SARS CoV-2

A novel muscle-driven method (MDM) with its corresponding Compute Unified Device Architecture parallel computational code is newly developed to mimic shortening and lengthening of muscles, in a fish-like swimming body, which causes the body flapping in the transversal direction and create a thrust force to propel the body to cruise in the longitudinal direction. In this method, the fish body is discretized