Abstract General defocusing particle tracking (GDPT) is a single-camera, three-dimensional particle tracking method that determines the particle depth positions from the defocusing patterns of the corresponding particle images. GDPT relies on a reference set of experimental particle images which is used to predict the depth position of measured particle images of similar shape. While several implementations

Abstract In this paper, the melting process of a PCM inside an inclined compound enclosure partially filled with a porous medium is theoretically addressed using a novel deformed mesh method. The sub-domain area of the compound enclosure is made of a porous layer and clear region. The right wall of the enclosure is adjacent to the clear region and is subject to a constant temperature of Tc. The left

Although the effect of pressure on the characteristics of laminar diffusion flame has been extensively studied, there is need of simple similarity correlations for flame shape and radiation fraction, which can be useful for application to turbulent flows and fire safety. In this paper, similarity analysis for flow and soot models is developed, where non-dimensional parameters were defined for the flame

The density and viscosity of pure liquid 2, 4-dichlorofluorobenzene and 2, 6-dichlorofluorobenzene were measured in the temperature range of (318.15–348.15) K at the local atmospheric pressure of 99.8 kPa. The saturated vapor pressures of pure 2, 4-dichlorofluorobenzene and 2, 6-dichlorofluorobenzene and the isobaric vapor-liquid equilibria (VLE) data for the 2, 4-dichlorofluorobenzene + 2, 6-dichlorofluorobenzene

The oblique drop impact on the thin film is numerically investigated in this paper with special attention paid to its splashing dynamics at moderate impingement angles (45° ≤ α ≤ 75°). A three-dimensional multiphase lattice Boltzmann flux solver associated with the diffuse interface method is adopted after being validated against reference data. Efforts are made to recover the complex flow features

Inertial and kinetic-Alfv'en wave turbulences have a priori little in common: indeed, the first one concerns rotating hydrodynamics in the limit of a small Rossby number (with $\bol$ the rotating rate) while the second describes high frequency plasmas in the limit of a strong uniform magnetic field B0. In this paper we show analytically that in the limit of local interactions in the perpendicular direction

An emergent property of decaying two-dimensional turbulence is shown to be a weak but persistent statistical heating, or tendency towards clustering of like-signed vortices. The rate of this heating, which is driven by changes to the vortex population due to vortex mergers and straining events, provides a strong constraint on both vortex decay laws and kinetic theories of vortex interactions. A quasi-equilibrium

Instability and transition in an elementary porous medium are investigated via global linear stability analysis and numerical simulation. The porous medium is presented by a representative elementary volume (REV) which consists of a staggered array of square cylinders. The stability analysis indicates the first critical Reynolds number at Re cr 84. Two unstable modes are captured from the linear stability

The flow behavior of entangled polymer solutions in simple shear flow is often assumed to be uniform, both in terms of the velocity gradient and polymer concentration. However, there is growing evidence of non-uniform “banded” transient or steady state flows of entangled polymer solutions. The present work considers a distinct phenomenon, whereby transient banding is concomitant with the presence of

Non-linear small amplitude high frequency vibrations affect mechanical systems leading to such effects as the stabilization of an inverted pendulum on a vibrating foundation and size-separation of particles of a granular material. These effects can be studies using the mathematical technique called the method of separation of fast and slow motions. When applied to fluid mechanics applications, the

Direct numerical simulations two-way coupled with inertial particles are used to investigate the particle distribution and two-way coupling mechanisms in turbulent open channel flow. In particular, the relationship between low- and high-inertia particles and the distinct large-scale motions (LSMs) and very-large-scale motions (VLSMs) which are characteristic of high-Reynolds number, wall-bounded turbulence

A numerical and experimental study on the process of droplet formation in a T-junction microchannel with a shear-thinning continuous phase is presented. Simulations are performed using a three-dimensional lattice Boltzmann multicomponent model. The shear-thinning behaviour is modeled using the Carreau-Yasuda model and validated with our experiments involving both Newtonian and non-Newtonian continuous

Thermal fluctuations are not large enough to lead to state changes in granular materials. However, in many cases, such materials do achieve reproducible bulk properties, suggesting that they are controlled by an underlying statistical mechanics analogous to thermodynamics. While themodynamic descriptions of granular materials have been explored, they have not yet been concretely connected to their

Characterizing the structural complexity of networks is a major challenging work in network science. However, a valid measure to quantify network complexity remains unexplored. Although the entropy of various network descriptors and algorithmic complexity have been selected in the previous studies to do it, most of these methods only contain local information of the network, so they cannot accurately

Stochasticity is introduced to a well studied class of recursively grown graphs: (u,v)-flower nets, which have power-law degree distributions as well as small-world properties (when u=1). The stochastic variant interpolates between different (deterministic) flower graphs thus adding flexibility to the model. The random multiplicative growth process involved, however, leads to a spread ensemble of networks

We present the study of the landscape structure of hard and soft spheres as a function of the packing fraction and of the energy. We find that, on approaching the jamming transition, the number of different configurations available to the system has a steep increase and that a hierarchical organization of the landscape emerges. We use the knowledge of the structure of the landscape to predict the values

Preferential contact process limited by contact capacity remarkably affects the spreading dynamics on complex networks, but the influence of this preferential contact in social contagions has not been fully explored. To this end, we propose a behavior spreading model based on the mechanism of preferential contact. The probability in the model that an adopted individual contacts and tries to transmit

Active processes play a major role in the formation of membraneless cellular structures (biological condensates). Classical coarsening theory predicts that only a single droplet remains following Ostwald ripening. However, in both the cell nucleus and cytoplasm there coexist several membraneless organelles of the same basic composition, suggesting that there is some mechanism for suppressing Ostwald

The interaction between the oscillatory boundary-layer flow induced by Faraday waves and a sedimentary granular layer was studied in a Hele-Shaw cell vertically vibrated. The experimental parameters were the vibration frequency f and acceleration a, and the particle diameter dp. At a critical value for the depth of the supernatant fluid layer, Δhc, it was observed a transition between a flat motionless

Particle-resolved direct numerical simulations (PR-DNSs) are employed to simulate flows past various stationary clusters of spheres in low-particle-Reynolds-number regime. The results show that the drag force at the interface between the dilute and dense phases is significantly different from the prediction of the traditional homogeneous BVK law (AIChE Journal, 2007, 53(2):489-501). The drag force

A PIV-based system has been set-up for the simultaneous measurement of the local propagation velocity and the flame stretch of laminar jet premixed flames. The contributions of the flame front curvature and the strain rate of the fresh gas flow to the flame stretch are separately discussed. Laminar jet flames of methane-air lean mixtures have been studied with a secondary flame in a coflow configuration

Selective Catalytic Reduction is a key technology for reducing nitrogen oxide (NOx) emissions of diesel engines, which requires the injection of urea–water solution (UWS) into the hot exhaust gas. The main objective of this paper is the development of a methodology for predicting the evaporation of urea-water sprays. For this reason a generic experiment was conducted in order to provide validation

A synthetic jet actuator is a fluidic device that produces a jet flow by the periodic ingestion of fluid into and expulsion of fluid out of a cavity across an orifice. Since such a mechanism transfers linear momentum to the fluid without introducing a net mass into the system over an actuation cycle, the synthesized jet is also termed a zero-net-mass-flux jet. Over the last two decades, synthetic jets

The directional motion of a two-dimensional droplet on an obliquely vibrated substrate is studied numerically. The time dependent droplet profile is decomposed by using a proper orthogonal decomposition (POD) method. Two dominant POD modes of the capillary wave are identified. The first mode is quasi-harmonic, which leads to an apparent wetted area difference between uphill and downhill stages of the

The velocity and friction properties of laminar pipe flow of a viscoelastic solution are bounded by the corresponding values for two Newtonian fluids, namely, the solvent and a fluid with a viscosity identical to the total viscosity of the solution. The lower friction factor for the flow of the solution when compared to the latter is tracked to an increased strain rate needed to enhance viscous dissipation

Structures in polymer drag-reduced turbulence have been examined by using a direct numerical simulation of viscoelastic turbulent channel flow for a high drag reduction (HDR) rate of ∼60%. In drag-reduced flow, the length scale of turbulence structures significantly increases, especially in the streamwise direction. Moreover, the outer turbulence structures in the viscoelastic flow differ from those

This study examines the simplest relevant molecular model of a polymeric liquid in large-amplitude oscillatory shear (LAOS) flow: rigid dumbbells suspended in a Newtonian solvent. For such suspensions, the viscoelastic response of the polymeric liquid depends exclusively on the dynamics of dumbbell orientation. Previously, the explicit analytical expressions of the zeroth, second, and fourth harmonics

Wave propagation in microtubules plays an important role in cell function and engineering applications. Interfacial tension and hydrostatic pressure significantly affect such wave propagation in liquid-filled microtubules, but it remains elusive how they influence the dispersion relation. To address this, we develop a theoretical model based on Flügge’s theory, with interfacial tension and hydrostatic

Vertically clamped flexible flags in an oncoming Poiseuille flow were numerically modeled to investigate the hydrodynamic interaction and dynamics of the flexible flags using the immersed boundary method. The number of flags modeled was increased step by step: a single flag, double flags, triple flags, and a large array of multiple flags were modeled. The flexible flags displayed a flapping mode or

Blood plasma separation may be one of the most frequent operations in daily laboratory analysis so that a highly efficient separation could save time, cost, and labor for laboratory operators. A numerical technique is demonstrated in this work to design a highly efficient microfluidic chip that can separate 64% plasma from blood with 100% purity. Simulations are carried out for the blood flow by a

Hydrodynamics and nutrient transport in a hollow fiber membrane bioreactor is studied by developing a two-dimensional mathematical model in Cartesian coordinates. In a more realistic scenario, the scaffold is considered to be elastic and deformable, which undergoes deformation with the applied pore pressure. A mixture model is used to deal with the scaffold matrix, cells, and the fluid present in the

Liquid–liquid slug flow heat transfer in microchannels has been an interesting topic of research to many researchers. However, the heat transfer studies available in the existing literature deal with stationary walls of the microchannels. In the present work, a modulated motion is prescribed to the walls of the channel in the transverse direction during oil–water slug flow between micro-parallel plates

A microshaft may become rough due to corrosion, abrasion, and deposition when it has been operating in a viscous fluid. It is of importance to investigate the effects and to estimate the level of the shaft’s surface roughness. In this study, we consider a bumpy shaft with its shape modeled by the product of two cosinoidal functions; the roughness ε is defined to be the ratio of the amplitude of the

Transport of droplets on surfaces is important for a variety of applications such as micro liquid handling and biochemical assays. Here, we report evaporation-induced attraction, chasing, and repulsion between a target pure aqueous (water) droplet and a driver aqueous mixture droplet comprising water and a lower surface tension and lower vapor pressure liquid on a high energy surface. It is observed

In this paper, vortex-dynamical perspectives were adopted to interpret the recently reported observation that the total viscous dissipation of off-center droplet bouncing varies nonmonotonically with the impact parameter [C. He, X. Xia, and P. Zhang, “Non-monotonic viscous dissipation of bouncing droplets undergoing off-center collision,” Phys. Fluids 31, 052004 (2019)]. The particular interest of

We investigate the electroosmotic flow of a quasi-linear viscoelastic fluid over a surface having charge modulation in narrow confinements. We obtain analytical solutions using a combination of regular and matched asymptotic expansions in order to describe the viscoelastic flow field and apparent slip velocity besides pinpointing variations of the flow rate and ionic currents due to the surface charge

In this work, the early time dynamics of low-viscosity liquid drops spreading in their saturated vapor on partially wetting surfaces are investigated by lattice Boltzmann numerical simulations. Attention is paid to the effect of vapor transport through condensation on the spreading process. We observe that the condensation current resulting from the slight supersaturation of the liquid vapor near the

In this article, a fully compressible two-phase flow model combined with a multi-component real-fluid phase equilibrium solver is proposed for cavitation modeling. The model is able to simulate the dissolving process of non-condensable gas through resolving the real-fluid phase change equations. A three-dimensional cavitating nozzle test is considered to validate the suggested model. The achieved numerical

Droplet nucleation, condensation, and transport is a ubiquitous phenomenon observed in various industrial applications involving power generation and energy conversion to enhance heat transfer. Recent studies have shown that electrowetting (EW) has emerged as a new tool to enhance pool boiling heat transfer. In these applications involving heat transfer through pool boiling, the interplay between the

Liquid drop impact on dry, solid surfaces has been studied to elucidate the role of control parameters, such as drop size, impact velocity, liquid properties, surface roughness, and wettability, on the mechanism of splashing phenomenon. It has been shown more recently that ambient gas plays a pivotal role in initiating the disintegration mechanisms leading to the ejection of secondary droplets from

Surface tension forces enable a liquid to rise against gravity when wettable tubes or porous media are in contact with the pool of liquid. While the rise dynamics in the media of homogeneous porosity are well known, those in heterogeneous porous media still remain poorly understood. Here, we employ a vertical channel formed by two parallel plates decorated with micropillars, as a simple model of bidisperse

This paper describes the dynamic mechanisms of bubbles and droplets moving in quiescent flows. An improved diffuse interface method is adopted to capture the interfacial evolution of a two-phase flow, which can effectively suppress the phenomenon of interface dispersion. Preliminary simulations of a circular bubble/droplet moving from rest are first performed, and then, the interface shapes and vorticity

Hydrodynamic instabilities, including Rayleigh–Taylor, Richtmyer–Meshkov (RM), and Kelvin–Helmholtz, induced turbulent mixing broadly occur in both natural phenomena, such as supernova explosions, and high-energy-density applications, such as inertial confinement fusion. Reshocked RM mixing is the most fundamental physical process that is closely related to practical problems, as it involves three

For millimetre to micron sized bubbles, floating at the free surface of different low viscosity fluids with different surface tensions, and then collapsing, we study the ensuing expansion of the outer radius of the hole (ro) at the free surface, as well as its velocity of expansion (uo). Since the thin film cap of the bubble disintegrates before the hole in it reaches the static rim, the hole expansion

Empirically, we find that parametric plots of mechanical loss angle vs complex shear modulus may depend neither on temperature [M. van Gurp and J. Palmen, “Time-temperature superposition for polymeric blends,” Rheol. Bull. 67, 5–8 (1998)] nor on average molecular weight [S. Hatzikiriakos, “Long chain branching and polydispersity effects on the rheological properties of polyethylenes,” Polym. Eng. Sci

Hydrogels with or without chemical cross-linking have been studied and used for biomedical applications, such as tissue repair, surgical sealants, and three dimensional biofabrication. These materials often undergo a physical sol–gel or gel–sol transition between room and body temperatures and can also be chemically cross-linked at these temperatures to give dimensional stability. However, few studies

The effects of viscoelasticity, here caused by polymer additives, on Rayleigh Bénard convection flows are investigated via direct numerical simulations at a marginally turbulent Rayleigh number. Simulations with a range of polymer length and relaxation time scales show heat transfer enhancement (HTE) and reduction (HTR). The selection of HTE and HTR depends strongly on the maximum extensional viscosity

Towering in many gorges of reservoirs and coastal zones, pillar rock masses may collapse and fall due to foundation crushing, and the impact on water by debris leads to impulse waves. In this study, the process of impulse wave induction by the gravitational collapse of granular piles was investigated using particle image velocimetry. The experimental results showed that the collapse process of partially

A large spherical bubble rising in quiescent liquid generally leads to the formation of a toroidal bubble (central breakup). In this paper, we investigate the bubble dynamics during the central breakup process using the three dimensional Volume of Fluid method implemented in OpenFOAM. The potential energy of the large bubble is converted into the kinetic energy of the liquid jet, resulting in the formation

This study uses a two-way dynamic coupled numerical model and laboratory experiments to investigate the interaction of two free-falling spherical particles in water. Two spheres, with identical diameters D and densities, are released side-by-side simultaneously in a water tank. The Reynolds number, based on the terminal velocity and diameter of the sphere, is Re = 1.36 × 104. The experimental and numerical

Exploration of newer geometrical structures for microsinks stems from the desire to achieve better cooling at a lower pressure drop for more compact electronic devices. In this study, a three-dimensional conjugate heat transfer analysis is performed for a novel microchannel heat sink (MCHS) with disruptive structures in an otherwise rectangular channel. Each of these structural units has a pair of