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

Two-phase water-steam flow conditions are frequently encountered in many engineering applications, including geothermal reservoirs. Although routine calculations are based on the multiphase Darcy’s law, the role of the topology of the flowing phases at the pore-scale is usually neglected in the estimation of relative permeabilities. Instead, the latter are frequently computed using empirical models

The phenomenon of cavitation is widely used in the chemical engineering and mineral processing industries to increase the efficiency of flotation processes. This work is devoted to numerical studies of cavitation phenomena in a flow past a solid particle under laminar and turbulent flow conditions. The particle size is varied between 10 microns and 100 microns. A CFD-based mixture model combined with

A numerical investigation of the binary collision of two off-centre unequal sized liquid droplets in the gaseous environment has been performed. The complete process of collision of droplets is dynamically simulated by solving the incompressible Navier-Stokes equations. Simulations are performed using three-dimensional, multiphase finite volume based solver in OpenFOAM platform. The gas-liquid interface

We study in extensive detail the flow of dry and wet gas-liquid foams through a narrow two-dimensional channel comprising a complex constriction. The effects of constriction profile and size of aperture, foam flowrate, liquid holdup and liquid viscosity are experimentally investigated and a sophisticated image analysis procedure is developed to extract local fields of foam flow and deformation. Foam

Flash boiling spray has been extensively investigated because it has the potential in improving spray atomization. However, some phenomena, such as flow rate reduction, exit velocity choke and drastic bubble generation near the exit, etc., cannot be explained by existing theory of subcooled liquid jet and spray atomization. The phase change process occurring inside the nozzle still needs further exploration

Optical photography and image analysis technology provide a non-intrusive and efficient research tool for the experimental research of multiphase bubbly flow. This paper presented a multi-frame image processing algorithm for measuring size and velocity of bubbles more accurately with bubble shadow images, especially in bubbly plume with serious overlapping in the bubble image. The raw images are the

Highly viscous flow in a large-scale pressure-swirl atomizer is studied by 1) 3d scale-resolving large-eddy simulations and volume-of-fluid method, and 2) experiments based on laser-Doppler anemometry, imaging techniques and pressure measurements. Here, a low Reynolds number regime (600 ≤ Re ≤ 910) is investigated by varying the mass flow rate of the water-glycerol mixture. The aim of the study is

Engine fuel spray modeling still remains a challenge, especially in the dense near-nozzle region. This region is difficult to experimentally access and also to model due to the complex and rapid liquid and gas interaction. Modeling approaches based on Lagrangian particle tracking have failed in this area, while Eulerian modeling has proven to be particularly useful. Interface resolved methods are still

With an interest on atomization in turbulent flows, and modeling alternatives to classic atomization models and Direct Numerical Simulations (DNS), the present work derives and tests two droplet-size distributions parametrized by local information about the flow. One distribution is heuristic and another one is based on the linear-eddy model. Predictions from these distributions are tested with numerical

Effects of the presence of solid particles on the terminal velocities, VB, of single bubbles in a narrow channel were investigated. The gap thickness of the narrow channel was 3 mm. The bubble diameter, dB, was varied from 7 to 20 mm. Air, purified water and fine silica particles of 4.1 μm diameter were used for the gas, liquid and solid phases, respectively. The volume concentration of the particles

We study low Reynolds number locomotion of a spherical viscous droplet, in an unbounded arbitrary Stokes flow, under the combined influence of an inhomogeneous surfactant (diffusiophoresis) and non-isothermal temperature (Marangoni effect) fields. The self-generated gradient of the surfactant concentration and the influence of the external temperature field are respectively mapped as a slip velocity

The work is devoted to experimental and computational studies of the behavior of water drop in a flow behind incident shock wave and verification of calculations on this basis. High-Speed visualization of the water drop interaction with the flow behind incident shock wave was obtained in the experiments at shock wave Mach numbers Ms=1.109-1.34 and Weber numbers We = 208 - 2260. Conditions consistent

The high-energy phenomenon of particle acceleration driven by cavitation bubble collapses has garnered research interests over the past few decades. Potential applications range from cavitation-induced drug delivery, chemical synthesis, sonochemistry to micro-machining operations. However, the acceleration mechanisms and the velocities attained by particles remain in huge contention. A novel particle

Modern internal combustion engines rely on a high pressure fuel injection system to deliver the fuel inside the engine. This high pressure fuel injection also results in additional complexities, one of which is the cavitation occurring due to large pressure drops inside the injector. The generation of cavitation pockets inside the injector is known to increase the turbulence locally, affecting the

Hydrodynamics of rod-like particles, found extensively in the chemical and process industry, is investigated here, using direct numerical simulations. A recently developed formulation of the smoothed profile method for rigid bodies is first validated for rod-like particles (rods) and then used to characterize the concentration effects on the static and dynamic properties of rods in the Stokes regime

In this work, a new model is introduced to determine the crossflow velocity required to dislodge permeating oil droplets at the surface of a membrane. Oil droplets at the surface of a membrane face either of four fates; namely, pinning, permeation, rejection, or breakup. The conditions at which the first three fates are realized have been, to a large extent, satisfactorily explored. The conditions

Studied in the present paper is the phenomenon of interaction of suspended particles with the fluid over a stretchable rotating disk. The physical insights into the resulting flow behavior and heat transfer rate of two phase equilibrium are the main targets. How the stretching contributes to the dusty flow character will be clarified. Governing equations of motion and energy are first transformed into

Phase-averaged dilute bubbly flow models require high-order statistical moments of the bubble population. The method of classes, which directly evolve bins of bubbles in the probability space, are accurate but computationally expensive. Moment-based methods based upon a Gaussian closure present an opportunity to accelerate this approach, particularly when the bubble size distributions are broad (polydisperse)

In this paper, the color-gradient lattice Boltzmann model (Saito et al., Phys. Re. E 98, 013305, 2018) is used to study 3D hydrodynamic corium jet breakup and fragmentation in sodium. Firstly, an in-house GPU-accelerated color-gradient lattice Boltzmann solver is introduced in detail. Then, the solver is validated by comparing the simulation results with two demo Wood's metal jet experiments. Finally

In this paper, the dynamics and dominant parameters of the bubble shape deformation and the drag coefficient during bubble rising were theoretically analyzed based on fundamental insight into the bubble motion. Modified models for the aspect ratio and drag coefficient applying to a wide range including saturate vapor-water conditions under high pressure (6.9 – 15.5 MPa) were finally proposed based

In this paper a numerical solver is developed in the OpenFOAM to capture the interface effects and dynamic characteristics of two-phase viscoelastic-Newtonian fluid flow for single and multi-mode viscoelastic models in linear and non-linear regimes. The code is based on finite volume method and the PIMPLE algorithm is used to couple the velocity and pressure terms. The dynamic mesh technique is used

The local slip behavior and flow fields near the gas-liquid interface (GLI) of a Newtonian liquid flowing past a superhydrophobic surface with periodic rectangular grooves are investigated using molecular dynamics (MD) simulations. The saturated vapor of the liquid fills the groove to form the GLI. A flat GLI is introduced by carefully adjusting the channel height to make the liquid bulk pressure equal

This paper analyses the local and time-dependent behavior of large-scale structures responsible for liquid circulation in gas-water flow of a 3-D cylindrical bubble column of high aspect ratio with a multiple orifice for uniform aeration. The large-scale flow structures play an important role in the mixing and the mass transfer while coherent structures dominate hydrodynamic characteristics of the

Brewing coffee is primarily considered an art rather than a business. Drinking coffee is a practice spread worldwide irrespective of race, age, and social extraction, making coffee the leading commodity in the fair trade movement. Its daily consumption has scientifically proven health benefits. Thus, such interesting features of coffee have stimulated a wide coffee-oriented scientific research addressing

The effects of soluble surfactant on the lateral migration of a bubble in a pressure-driven channel flow are examined by interface-resolved numerical simulations. The interfacial and bulk surfactant concentration evolution equations are solved fully coupled with the incompressible Navier-Stokes equations. A non-linear equation of state is used to relate interfacial surface tension to surfactant concentration

In the present study, a large eddy simulation was conducted to simulate the three-dimensional cavitation turbulence flow inside a Helmholtz oscillator under a high Reynolds number. Numerical results show reasonable agreement with available experimental observations and data. Under the validated solution strategy, the cavitation flow is visualized in a straightforward manner and indicates the primary

In the present study, an experimental study was conducted to characterize the effects of initial ice roughness on the transient behaviors of surface water/ice run-back over a NACA 23012 airfoil model under a glaze icing condition. The experimental study was conducted in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT). A digital image projection (DIP) technique was applied to provide

In the present work, different closure relations in the one-dimensional Two-Fluid Model were investigated in order to assess the effect on the numerical simulation of vertical annular flows, including the formation and propagation of waves at the gas-liquid interface. Different interfacial friction formulations, momentum flux parameters and dynamic pressure terms were employed. The conservation equations

The behavior of low-speed liquid jets emerging from rectangular orifices into a quiescent air is studied numerically. After ejection, the rectangular cross-section transforms into an elliptical form along the jet and while axis-switching includes elliptical cross-sections only, the rectangular shape never establishes again. The optimum wavenumber, corresponding to the most dominant wave, is found to

Direct numerical simulations of fully developed turbulent channel downflow at bulk Re equal to 6300, loaded with monodisperse bubbles at gas volume fractions α=0.5%, α=2.5% and α=10% have been carried out. Bubble deformability, surface tension, as well as discontinuity in the material properties across the bubble interfaces are explicitly accounted for. A full-scale channel of size 4πH × 2H × 4πH/3

The atomization and combustion characteristics of fuels injected in aviation gas turbine engines are very important in the research and development of gas turbine combustors and have a significant impact on engine efficiency and pollutant emissions. In this study, spray atomization characteristics of pre-filming airblast nozzles developed for use in aviation gas turbine combustors were experimentally

Neutrally buoyant colloids with small Reynolds numbers pose interesting challenges particularly when they undergo shear thinning and Brownian diffusion. Two basic flows including Poiseuille and Couette flows accompanying shear-induced particle migration are investigated in this study using direct numerical simulations (DNSs). A scaled viscosity model of colloidal suspensions considering both the shear

The process of water entry is a complex and attractive field of research, since from more than a century ago there are wide applications in industry, nature science, bionics, and naval technology. The objective of this work is to investigate the cavity dynamics during water entry of a spinning sphere by numerical simulations. The algorithm of these simulations uses the Boundary Data Immersion Method

In this study, the deposition of fibrous particles in a realistic 3D model of the right nasal cavity of a 24-years-old woman was simulated using the non-creeping formulations for hydrodynamic forces and torques. The Lagrangian trajectory analysis approach within the Ansys-Fluent software was used for these simulations. Several user-defined functions (UDFs) for solving the coupled translational and

We present an anisotropic, dynamic multi-phase turbulence model for moderately dense gas-particle flows by spatially averaging the kinetic-theory based two-fluid model (Schneiderbauer, AIChE J., 2017; 63(8): 3544 – 3562). The filtered gas-particle drag force can be approximated by the resolved drag force corrected by the drift velocity (Parmentier et al., AIChE J., 2012; 58(4): 1084 – 1098). The drift

We perform an experimental analysis of stratified, co-current gas-liquid flow in a straight pipe, with the aim of investigating secondary flow structures in the gas-phase. Planar PIV (particle image velocimetry) of the pipe centerline as well as stereoscopic PIV of the pipe cross section is performed, considering cases where the interface is either rough (wavy) or flat. Results demonstrate that the

We present an experimental study to investigate the impact of bubble size on behavior of bubble plumes from the integral point of view. Two distinct types of bubble plume were generated under the same volumetric gas flow rate: many small bubbles using an air-stone diffuser and a few large bubbles using a single-orifice diffuser. Using Particle Image Velocimetry, we measured the velocity field in the

The influence of the ambient pressure on the breakup process is investigated by means of PIV and shadowgraphy in the configuration of a planar prefilming airblast atomizer. The ambient pressure is varied from 1 to 8 bar. Other investigated parameters are the gas velocity and the film loading. From single-phase PIV measurements, it is found that the gas velocity in the vicinity of the prefilmer partly

Dual-tip phase-detection probes can be used to measure flow properties in gas-liquid flows. Traditionally, time-averaged interfacial velocities have been obtained through cross-correlation analysis of long time-series of phase fraction signals. Using small groups of detected particles, a recently developed adaptive window cross-correlation (AWCC) technique enables the computation of pseudo-instantaneous

The modulation of turbulence by sub-Kolmogorov particles has been thoroughly characterized in the literature, showing either enhancement or reduction of kinetic energy at small or large scale depending on the Stokes number and the mass loading. However, the impact of a third parameter, the number density of particles, has not been independently investigated. In the present work, we perform direct numerical

Starting from the full continuum mechanical description of free surface flows, a model for the rise of a liquid in a capillary is derived. The derivation improves on several aspects: Firstly, the influence of a slip boundary condition on the capillary wall is added to the model. Secondly, the stationary rise height is corrected. Thirdly, a regularization is suggested that uses the mass in interface

The present paper is Part Ⅱ of an investigation into void fraction measurement and modeling in a triangular-array rod bundle geometry under high-pressure conditions (P =5–9 MPa and G =100–350 kg•m−2•s−1). In Part I of the study, the experimental facility and measurement techniques were described, and the measured local, chordal, and area-averaged void fractions were presented and analyzed. In this

The outwardly propagating spherical flames in premixed gas containing water droplets are theoretically studied in this work. The correlations between the flame propagation speed, droplet distribution and flame radius are derived, based on the large activation energy and quasi-planar flame assumptions. With this, flame bifurcation and multiplicity are analysed, focusing on the effects of initial droplet

Evaporation rates of low-density water aerosols in a cylindrical acoustic resonator were investigated experimentally, motivated by the potential use of water droplet aerosols in two-phase thermoacoustic devices. Measurements of water aerosol evaporation rates were conducted using a novel direct visualization method combining mass balance quantification based on the light scattering from water droplets

Understanding the near-field region of a spray is integral to optimization and control efforts because this region is where liquid break-up and spray formation occurs, setting the conditions under which the spray dynamics evolve under the gas turbulence and droplet inertia. However, the high optical density of this region complicates measurements; thus, it is not yet well characterized. This paper

Three-dimensional direct numerical simulations of dense suspensions of monodisperse spherical particles in simple shear flow have been performed at particle Reynolds numbers between 0.1 and 0.6. The particles translate and rotate under the influence of the applied shear. The lattice Boltzmann method was used to solve the flow of the interstitial Newtonian liquid, and an immersed boundary method was

We present a particle method for estimating the curvature of interfaces in volume-of-fluid simulations of multiphase flows. The method is well suited for under-resolved interfaces, and is shown to be more accurate than the parabolic fitting that is employed in such cases. The curvature is computed from the equilibrium positions of particles constrained to circular arcs and attracted to the interface

The interaction and drag coefficient of three horizontal bubbles with a large bubble (BL) and two side symmetrical small bubbles (BS) in the shear-thinning fluids were simulated numerically using the three-dimensional volume of fluid (3D-VOF) method. The effects of the initial diameter of BL, initial bubble interval and liquid property on the rising velocity and drag coefficient of bubbles were studied

Spray reactive flow finds application in various technical devices, and due to the complex nature, their optimization is very challenging, requiring proper modeling of turbulence/chemistry interactions as well as of the contribution from spray evaporation. This work presents a study of sub-grid scale combustion models, where relevant assumptions on multiphase coupling and their effects are analyzed

The present work aims for the isolated investigation of the influence of system pressure on spray quality of twin-fluid atomizers. An approach of pressure adapted nozzles was applied, allowing for constant mass flows, gas-to-liquid ratio as well as fluid velocities at the nozzle orifice independent of system pressure. Two Newtonian liquids featuring viscosities of 1 and 100mPa · s were used, varying

Electric field has been proven to be an effective active technique in microfluidic devices for precise manipulating of the microdroplet. In this article, we investigate the Water in Oil droplet formation in a flow-focusing microchannel under AC electric field experimentally and numerically. A three-dimensional numerical model is built combining the Volume of Fraction (VOF) method and the leaky dielectric

Effects of the computational domain size on inertial particle one-point statistics are presented for direct numerical simulations of turbulent open channel flow at a moderate Reynolds number, which are seeded with two-way coupled particles at low volume concentration (less than 1.5×10−3, for such particle load the one-way coupled particles scheme is also valid). Particle one-point statistics across

Laboratory experiments were conducted to study the dynamics of particle clouds released vertically downward into stagnant water. The importance of nozzle diameter, sand particle mass, and particle size were studied in the form of an aspect ratio and Stokes number. The axial and radial profiles of sand concentration and velocity of particle clouds were measured by an accurate and robust optical probe

The boundary element method is adopted to study the ventilating axisymmetric bubble growth from a circumferential slit in a submerged cylindrical wall under vertical flow conditions in this paper. During the bubble growth, mesh subdivision and smoothing techniques are adopted in order to optimize mesh topology. In this study, the effects of inflow velocity, surface tension coefficient, ventilation