Models for prediction of drag forces within a particle cloud following shock-acceleration are evaluated with the aid of results from particle-resolved simulations in order to quantify how much the disturbances introduced by the proximity of nearby particles affect the drag forces. The drag models evaluated here consist of quasi-steady forces, undisturbed flow forces, inviscid unsteady forces, and viscous

The interfacial structure of annular flow in upward inclined pipes is examined experimentally by a non-intrusive multilayer conductance liquid film sensor (LFS). In horizontal and inclined pipes, cross-sectional distribution of gas and liquid phases is asymmetric even on average. Thus, the ratio between the characteristic film thickness and the mean dominant wave parameters may vary significantly as

The present work studies the dynamics of large and small bubbles in sudden expansions and contractions in vertical pipes. The experimental apparatus was designed to permit changes in flow patterns through singularities provoked by an expansion followed by a contraction. The data were obtained through particle image velocimetry and the shadow sizer technique. Size and velocity distributions for small

Secondary breakup is a common phenomenon in nature, as well as in industrial applications. The secondary breakup of Carboxymethyl cellulose (CMC) droplets in a continuous air jet flow is investigated experimentally by a high-speed digital camera. Through varying the Weber number and the Ohnesorge number in the experiment, the breakup morphology, deformation stage, and breakup regime map are discussed

We investigate the dynamics of a millimetre-sized air bubble rising in a liquid due to buoyancy under the influence of a magnetic field applied in a direction transverse to the bubble motion by conducting three-dimensional numerical simulations. The path and trajectory of the air bubble are examined by varying the strength of the transverse magnetic field. In the absence of a magnetic field, it is

This work focuses on boiling heat transfer studies during cooling liquids flow (FC-72, HFE-649, HFE-7000 or HFE-7100) along a single minichannel of 1.7 mm depth, vertically or horizontally oriented. The temperature of the outer smooth side of the plate was measured by infrared thermography. The observations of the flow structures were carried out on the enhanced side of the plate contacting fluid.

We present a simple and practical adaptive finite difference method for the conservative Allen–Cahn–Navier–Stokes system. For the conservative Allen–Cahn equation, we use a temporally adaptive narrow band domain embedded in the uniform discrete rectangular domain. The narrow band domain is defined as a neighboring region of the interface. The Navier–Stokes equation is solved in a fully discrete domain

We have performed spectral/spectral-element simulations of a single oblate spheroid with small geometrical aspect ratio settling in an unbounded ambient fluid, for a range of Galileo numbers covering the various regimes of motion (steady vertical, steady oblique, vertical periodic and chaotic). The high-fidelity data provided includes particle quantities (statistics in the chaotic case), as well as

Recent experimental results demonstrate that electric field can effectively decrease the melting time of dielectric Phase Change Materials (PCMs). In this study, a Finite-Volume Method (FVM) based numerical model for the solid-liquid phase change heat transfer of dielectric PCM under the influence of electric field is presented. Fully coupled governing equations of electric potential, charge transport

In this work the capabilities of Two Fluid Model simulations coupled with a Population Balance Model solved with the Quadrature Method of Moments in predicting the turbulent kinetic energy dissipation rate and the droplet size distribution in a dilute liquid-liquid stirred tank are investigated. For a strict evaluation of the numerical and modelling approximations, original two-phase flow fields and

Normal planar laser induced fluorescence (N-PLIF) method has been widely applied in liquid film imaging and thickness measurements in circular tubes with large curvatures, but meets great challenges in liquid film thickness measurements in circular tubes with small curvatures or at plates. An alternative method is to place both the incident laser sheet and the camera below the bottom interface of a

The inner velocity structure and particle concentration profile of opaque turbidity currents were measured simultaneously by ultrasound velocity profilers. Currents consisting of a quartz particle suspension were generated by using the lock-exchange method in a flume to experimentally reproduce the quasi-steady state of a turbidity current. A pair of ultrasound transducers captured the horizontal and

Post critical heat flux (post-CHF) heat transfer may occur during loss of coolant accidents (LOCAs) in water-cooled nuclear reactors when makeup water quenches the uncovered portion of fuel rods in the reactor cores. Post-CHF flow regimes include inverted annular film boiling (IAFB), dispersed flow film boiling (DFFB), and a transition regime between these two, i.e., inverted slug film boiling (ISFB)

The interaction of a shock wave and particles filling the inside of a straight tube was numerically investigated to understand the mitigation mechanism on a blast wave outside the tube. A shock wave propagating along the particle layer inside the straight tube induced differences in the velocity and temperature between the particle layer and shocked air, inducing energy transfer through a drag effect

In this paper we present a new multiphase computational model for polydisperse turbulent gas-liquid flows. In this model the gas phase is transported by a single convection equation and the effect of turbulent dispersion is addressed by including a diffusion term. In order to close the system of equations, the gas phase velocity is calculated by employing the slip velocity concept or by solving an

The dynamic interaction of a fluid particle with a continuous phase has been often a topic of study, for its broad range of applications in various industries. Better understanding of particle-fluid interface instability can assist to enhance the efficiency of different processes and possibly avoid unfavorable consequences. In the present work, a weakly nonlinear instability analysis is performed to

Air bubbles entrained in ocean breaking waves play various roles in air–sea gas transfer, wave energy dissipation, and surface layer mixing. While sub-mm bubbles dominate the distribution of sizes observed in bubble plumes created by breaking waves, the dynamics of such microbubbles in a swarm are poorly understood, and most previous experimental and computational studies have focused on the behavior

A parametric study on the stability and morphology of the liquid cone in a flow focusing process is carried out through experimental and numerical methods. For the numerical simulations, we solve the Navier-Stokes equations coupled with a diffuse interface method. A scaling analysis which considers the competition between the viscous shear stress and the interfacial tension force is proposed, showing

A two dimensional incompressible smoothed particle hydrodynamics scheme for long term sedimentation of rising or falling particulates (bubbles, drops or rigid particles) in Newtonian fluids is presented and validated by simulating the sedimentation of a single elliptic disc. The proposed method is then used to simulate the sedimentation of an elliptic disc subject to an external electric field parallel

In the present study, we assessed the capabilities of Eulerian-Eulerian CFD two-phase flow simulation with the homogeneous Multiple Size Group Model (MUSIG) and consideration of breakup and coalescence under three-dimensional flow conditions. We compared void fraction, bubble size and bubble velocity distributions against experimental data from vertical gas-disperse two-phase flow in a pipe with a

The particle-source-in-cell Euler-Lagrange (PSIC-EL) method is widely used to simulate flows laden with particles. Its accuracy, however, is known to deteriorate as the ratio between the particle diameter (dp) and the mesh spacing (h) increases, due to the impact of the momentum that is fed back to the flow by the Lagrangian particles. Although the community typically recommends particle diameters

Single CO2 bubbles rising in quiescent viscoelastic polyacrylamide (PAA) aqueous solutions of different weight percentages (wt. %) were studied to obtain insight into the impact of fluid elasticity on the rising dynamics of dissolving bubbles. A random abrupt fall and rise in velocity was observed as the bubble velocity gradually and progressively decreased throughout the journey. This is the first

A recently published pressure-based compressible multiphase flow model Labois and Narayanan (2017) is validated for applications relevant to safety of pressurized systems, such as flashing of high-pressure water through valves and nozzles. The pressure-based compressible multiphase flow solver is based on non-conservative discretization of the mixture continuity equation and has the advantage of being

The objective of this study is to understand the dynamics of freely evolving particle suspensions over a wide range of particle-to-fluid density ratios. The dynamics of particle suspensions are characterized by the average momentum equation, where the dominant contribution to the average momentum transfer between particles and fluid is the average drag force. In this study, the average drag force is

We experimentally investigated the kinematics and suspension of particles in the near-wall region of a horizontal turbulent channel flow of water. The particles were glass beads with a diameter of 0.014H, where H is the full channel height. The experiments involved dilute particle suspensions at bulk volumetric concentrations (ϕ) of 0.05, 0.12, and 0.27%, and at Reynolds numbers (Re) of 20,200, 40

An accurate shock- and interface-capturing method is introduced for simulations of compressible multiphase flows. First, an associated Godunov-type numerical scheme is established for a five-equation two-phase model obtained from a seven-equation model by assuming a single velocity and a single pressure between two phases. The computational finite-volume Riemann solver using the scheme and computing

Understanding the physics of primary liquid breakup process and its correlation with the evolution of spray characteristics in a rotary slinger atomizer is the goal of the present research. Experiments were conducted in a high-speed slinger test rig that houses a static liquid delivery manifold to uniformly supply the liquid to the rotating slinger disc that contains a single row of orifices carved

This experimental work deals with the motion behavior of adhering water droplets under the influence of gravity and harmonic surface vibration. Two different substrates with moderate static contact angles (74°-105°) are used and surface vibration is applied separately in vertical and horizontal directions. The experiments comprise different droplet volumes (3-20 µl) and various plate inclinations (0°-30°)

The shear layer on a supercavity wall is the gas entrainment channel to wake flow for ventilated supercavitating flows with various tail closure modes. To thoroughly understand the gas loss mechanism and the relationship between the gas loss mechanism and dynamic stability of the flows, the flow structures and associated characteristics in the shear layer must be studied. The multi-fluid model used

Continuum methods are efficient in modeling multi-phase flow at large time and length scales, however, their applicability to nanoscale systems and processes is questionable. When mean free path and average time between atomic collisions are comparable to the characteristic length and time scales of interest, the continuum hypothesis approaches its spatial and temporal limit. Here we discuss the implications

The present study conducts an experiment on water lubricated oil-water flow inside a horizontal pipe designed with a 90° elbow, in which the selected test fluids are mineral oil and tap water with a viscosity ratio of approximately 1000 and density ratio of 0.9. Measurements are recorded for the flow rates of oil and water from 10.60 to 28.26 L/min and 3.83 to 14.13 L/min, respectively, with the water

When a gas phase is injected into a liquid phase, it gives rise to a rich, fascinating and mysterious fluid dynamic phenomenology. The lack of knowledge regarding this phenomenology, a shortcoming in the design and operation of multi-phase reactors, is related to the absence of an unique definition of the flow regimes. To date, different studies gave different definitions of the flow patterns and,

Fundamental study on breakup of the supercooled large droplet is important for understanding the microphysical phenomenon in aircraft icing. The deformation and breakup processes of water droplets with diameters in the range of 700 to 1000 microns injected into continuous air jet flow are investigated experimentally. Evolutions of the bag, the bag and stamen and the dual breakup morphology are recorded

Compressible multiphase numerical simulations of gas-focused micro-jets are compared with the experimental data obtained with the dual pulse imaging laser-induced fluorescence drop velocimetry. Such jets, originating from a 3D printed gas dynamic virtual nozzle into a low-vacuum (150 Pa) environment, are increasingly being used for sample delivery in serial femtosecond crystallography. The distance

The requirement of high-fidelity experimental data of microscopic properties of sprays motivates the continuous development of optical tools, since they are determinant in the understanding of atomization and evaporation process in a variety of multiphase flows.This work compares two optical techniques and an interferometry method for the measurement of the droplet size and velocity of a spray produced

Two-phase flow boiling is susceptible to the Ledinegg instability, which can result in non-uniform flow distribution between parallel channels and thereby adversely impact the heat transfer performance. This study experimentally assesses the effect of thermal coupling between the parallel channels on flow maldistribution caused by the Ledinegg instability and compares the results to our prior theoretical

A technique for Lagrangian tracking of bubbles and detecting their time-evolution behaviors is presented. Five possible behaviors are considered: formation, extinction, continuity, binary fragmentation, and binary coalescence. The technique is based on establishing a network of mappings between bubbles identified at adjacent time instants. The mappings are determined by selecting the minimum from a

Long time simulations of the dispersion of prolate spheroids in a turbulent channel are performed to study the effect of the averaging procedure on particle statistics. The turbulent flow at Reτ=180 is directly simulated (DNS) and 300000 ellipsoids, modelled as point-particles are tracked to produce statistics. After a long time, an initially uniform particle distribution reaches a steady state in

Multiphase flow models involve more variables than available equations, thus constitutive equations are required to solve the system's governing equations. In the Drift Flux Model, mean drift velocity of the gas phase is estimated by using a Dispersed-Phase Distribution Coefficient and Gas Drift Velocity closure relationships. This study investigates the hydrodynamic of the slug flow regime with high-viscous

In this paper, the unsteady cavitating flow around a symmetrical twisted hydrofoil is investigated numerically. Cavitating flow characteristics are analyzed in terms of dynamical behaviors and temporal/spatial fluctuations of the cavities along the hydrofoil. At the midsection of the foil, sheet cavity firstly grows with nearly constant speed until the occurrence of the reverse flow at the closure

Capturing the dynamics of the triple contact line at the base of a vapor bubble is crucial to the development and validation of boiling heat transfer and boiling crisis models. To this end, laser-based techniques are the state-of-the-art. However, they have technical limitations, e.g., due to the presence of parasite interference patterns or laser speckle, and are often complicated to implement and

Experiments are performed in low-inclination (≤ 5°) upward stratified oil (Exxsol D140) and water flows. The flows are investigated using a novel two-line laser-based diagnostic measurement technique that combines planar laser-induced fluorescence and particle image/tracking velocimetry to obtain two-dimensional (2-D) space- and time-resolved phase and velocity information. The technique enables direct

The collision of two fluid particles with similar sizes approaching each other with time dependent velocities is studied in this work via a film drainage model that can render both coalescence and rebound. The model equations are simplified following the lubrication theory and the interfaces are treated as deformable ones. The particle velocities are governed by a force balance that includes the added

The distribution of particles in a jet with an initial bias is assessed using planar nephelometry, which is a planar imaging technique using Mie-scattering. Initial biases in particle distributions can have large and significant effects, particularly in solid fuel combustion systems, where inhomogeneities will affect the local and global performance of a flame. In this study, a two-phase jet flow with

We use direct numerical simulations (DNS) to investigate the turbulent modulation due to the presence of bubbles in vertical channels flowing downward. The Reynolds number for single-phase flow based on half channel height h* and friction velocity is Reτ= 180. A density and viscosity ratio of ρd*/ρc*=0.01 and μd*/μc*=0.018 is chosen for two void fractions of ϵ=1.2% and ϵ=2.4%. For each void fraction

We use direct numerical simulation based on the level contour reconstruction method to investigate head-on droplet collisions with dry, stationary, spherical particles. Three important impact parameters are varied over broad ranges: Weber number (4 ≤ We ≤ 150), surface wettability (20° ≤ θeqi ≤ 160°), and droplet-to-particle-size ratio (1/3 ≤ Ω ≤ 2), leading to a total of 225 collision scenarios being

The stability of a falling liquid film flowing down an inclined channel is revisited. The classical Kapitza criterion for the onset of long wave instability ignored the presence of the adjacent gas phase and provided the critical liquid Reynolds number, Recr=5/6cot(β) for the flow destabilization. In the current study, the impact of the adjacent gas on Recr is studied via solution of the Orr-Sommerfeld

Multiphase flow phenomena have been widely observed in the industrial applications, yet it remains a challenging unsolved problem. Three-dimensional computational fluid dynamics (CFD) approaches resolve of the flow fields on finer spatial and temporal scales, which can complement dedicated experimental study. However, closures must be introduced to reflect the underlying physics in multiphase flow

This study experimentally investigated the wetting process of an oil droplet impacting on the dry surface with different surface roughness (0.3 μm, 1.6μm, 2.9μm, 5.2 μm) from the front view. Experiments were conducted under three impacting Weber ranges with the inclined angles of 37.0°, 63.0°, and 75.5°. The droplet spread as a ‘pancake’ on the surface when the inclination angle was 37.0°, while the

Dual-tip phase-detection intrusive probes are the most widely used experimental technique for measuring interfacial velocities in highly aerated flows. Recently, we have introduced an adaptive window cross-correlation (AWCC) technique, which allows for the estimation of pseudo-instantaneous velocities and associated velocity statistics. Several potential limitations of this technique were suggested

Accurate characterization of surface roughness and understanding its influence on multiphase flow behavior are important for industrial and environmental applications such as enhanced oil recovery, CO2 geological sequestration, and remediation of contaminated aquifers. Although some experimental and simulation studies have been conducted for investigating surface roughness in regular geometry structures

Direct numerical simulation (DNS) has been widely employed to study the dynamics of turbulent bubbly flows; however, it is used in a limited setting, namely, turbulent bubbly channel flows with low density ratio and low Reynolds number. The present study aims to overcome these limitations and simulate turbulent bubbly pipe flow of a water-air system, a common experimental setting, with high density

This paper concerns modeling of the evolution of the intermittency region between two weakly miscible phases due to temporal and spatial variations of its characteristic length scale. First, the need for a more general description allowing for the evolution of the intermittency region is rationalized. Afterwards, results of the previous work (Wacławczyk T., 2017, On a relation between the volume of

Slug flow is an intermittent and complex gas-liquid flow pattern, that can cause severe problems in industrial operations and lead to large uncertainties in multiphase flow metering. These problems are primarily caused by the liquid slugs of the flow. In this context, different cases of slug flow in horizontal pipes are investigated to find a statistical characterization of the slugs in time and space

In the present paper, an enhanced Volume of Fluid model is applied for the conduction of parametric numerical simulations, to investigate break-up phenomena of accelerating, elongated, vapour bubbles, within circular mini-channels. The effect of fundamental controlling parameters in the resulting break-up characteristics is investigated. Four different series of parametric numerical simulations of

The vaporization rate of reacting aluminum droplets in high-speed flows plays a crucial role in determining the energy released during the combustion of aluminized solid propellants and explosives. This work develops a model for the vaporization rate of burning aluminum droplets in shocked flows using data from high-resolution simulations. A levelset-based sharp-interface method is used to resolve