Metal particles in solid propellants enhance rocket engines performance. An interaction of particles with a high Reynolds number turbulent gas flow accelerating to a nozzle, has not been characterized thoroughly. We study the particle-turbulence interactions in a two-dimensional model of a rocket engine. Two-phase particle image/tracking velocimetry provides the flow velocity simultaneously with the

We analyse the controlled generation of bubbles of a given size at a determined bubbling rate in a co-flowing water stream forcing the gas flow. The temporal evolution of the bubble size, R(t), the air flow rate, Qa(t), and the pressure evolution inside the bubble, pb(t), during the bubbling process are reported. To that aim, the temporal evolution of the bubble shape and the pressure inside the air

In the suspension high velocity oxy fuel (SHVOF) thermal spray, a suspension is injected into the combustion chamber where the jet undergoes primary and secondary breakup. Current knowledge of the primary breakup within the combustion chamber is very limited as experimental investigations are impeded due to direct observational inaccessibility. Numerical methods are also limited due to the computational

The evolution of interfacial waves is investigated for a stratified laminar-laminar flow in a plane channel using numerical simulations based on the Volume of Fluid (VOF) method. Different nonlinear instability mechanisms that can promote saturation or rapid amplification of interfacial waves are investigated. Controlled disturbances are introduced at the interface between the two fluids, to assess

The experiments of co-current vertical upstream air-water two-phase flow in a 66 mm × 66 mm square channel were carried out. The superficial liquid velocity ranges from 0.765 m/s to 1.53 m/s and the superficial gas velocity ranges from 0.0215 m/s to 0.313 m/s, including bubbly flow and cap-bubbly flow. A dual wire-mesh sensors (WMSs) was used to measure the bubbles in the two-phase flow. The local

The efficacy of NOx reduction in diesel engines is mainly dependent on how uniformly urea-water solutions (UWS) are dispersed onto the catalyst surface of the Selective Catalytic Reduction (SCR) systems. The urea-based SCR systems also suffer drawbacks due to the formation of urea deposits onto the walls of after-treatment devices due to poor atomization characteristics of UWS. In this work, the impact

Three-dimensional Direct Numerical Simulations (DNS) data has been used to analyse the gaseous phase combustion behaviour in a V-shaped flame configuration where fuel is supplied in the form of droplets such that an overall (i.e. liquid+gaseous) equivalence ratio of unity is maintained in the unburned gas. The analysis has been carried out for different initially mono-sized droplet diameters. A gaseous

Multiple spatial scale is an important characteristic of two phase flow phenomena. The micro-scale and macro-scale flow structures are obviously different in flow state and have different effects on the mass, momentum and energy transfer between two phases. Different modeling approaches have been developed for each scale physical phenomenon in traditional numerical simulations. However, it is difficult

The paper considers the approaches frequently used to model pressure drop in a granular layer. These are a model of a hydraulic circuit element, a Lockcart-Martinelli model, and a generalization of the Darcy-Forchheimer model. A new model, representing a generalization of the gas dynamics equations to a two-phase flow, is proposed. The results of the considered models verification by two groups of

Previous works for a liquid suddenly contacting a gas at a supercritical pressure show the coexistence of both phases and the generation of diffusion layers on both sides of the liquid-gas interface due to local thermodynamic phase equilibrium. A related numerical study of a laminar mixing layer between the liquid and gas streams in the near field of the splitter plate suggests that mass, momentum

This work presents an experimental study focusing on the interactions between the dispersed and Taylor bubbles in a slug flow pattern. In order to better investigate these interactions, a quasi-real slug flow was studied, where a single Taylor bubble is injected in a bubbly flow background stream, under controlled and repeatable conditions, controlling the bubbly flow superficial gas and liquid velocity

Owing to the transient nature of microchannel flow-boiling, gaining an in-depth understanding of the associated trends in time-averaged heat transfer variables as well as mechanisms of heat transfer is quite challenging. This work studies sub-cooled flow-boiling of de-ionized water in a microchannel. The micro-channel heights studied are 0.14, 0.28 and 0.42 mm while the tested mass fluxes range from

The results of Direct Numerical Simulations of the oscillatory flow over a cohesionless bed of spherical particles, mimicking sediment grains, are described. The flow around the sediment particles is explicitly computed by using the immersed boundary method, which allows the force and torque acting on the particles to be evaluated along with their dynamics. Different values of the Reynolds number and

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

Propagation of one-dimensional planar flames laden with fuel droplets is theoretically investigated in this work. Localized homogeneous and heterogeneous flames are considered, characterized by different relative locations of dispersed droplets and propagating flame front. With the assumption of large activation energy for the chemical reaction, correlations describing flame propagation speed, flame

It is very meaningful to measure the oil fraction of oil-water dispersed flow in pipelines. Traditional single-frequency ultrasonic methods measure the oil fraction by treating the dispersed flow with an average droplet size, which ignores the influence of the droplet size distribution and limits the measurement accuracy. Therefore, a swept-frequency ultrasound attenuation method based on droplet size

Nanofluids have attracted interest for their high performance in enhancing heat transfer and improving combustion. However, few studies have investigated the influences of nanoparticles on spray processes. In this study, the surface waves, liquid column oscillation, and droplet size distribution of a nanofluid transverse jet were investigated at low gas Weber number. A new statistical image-processing

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

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

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

Numerical simulation of tip vortex cavitation (TVC) remains a challenging task in a variety of applications, such as axial turbines and pumps as well as marine propellers. Although it is well known that TVC is highly sensitive to gas content, be it dissolved or not, numerical models do not consider this aspect so far. As a result, numerical simulations usually underestimate the development or the intensity

COVID-19 pandemic has strikingly demonstrated how important it is to develop fundamental knowledge related to generation, transport and inhalation of pathogen-laden droplets and their subsequent possible fate as airborne particles, or aerosols, in the context of human to human transmission. It is also increasingly clear that airborne transmission is an important contributor to rapid spreading of the

Temporal and spatial-resolved data on the interfacial structure in upward vertical and inclined two-phase annular flows were accumulated using a novel non-intrusive multilayer conductance sensor. The sensor provides simultaneous measurement of the film thickness across the entire pipe circumference, enabling a three dimensional reconstruction of the wavy interface. Measurements were performed for two

The underwater noise radiated during the impact pile-driving of offshore foundations is a major threat to the habitat of several marine creatures. The bubble curtain is a widely used noise mitigation system. A major uncertainty in modeling the acoustic properties of a bubble curtain is the unknown local bubble size distribution. For an accurate estimation, a buoyant jet integral model of a bubble plume

The complex mechanism behind the laser-induced cavitation bubble has led to challenges in its modeling. Current models can only predict the radius of the single laser-induced cavitation bubble over one or two growth and collapse cycles. To fill the gap, we propose a new model that takes into account the liquid compressibility, heat transfer, and non-equilibrium evaporation and condensation. Specifically

We experimentally investigate the influence of alternating rough and smooth walls on bubbly drag reduction (DR). To this end, we apply rough sandpaper bands of width s between 48.4mm and 148.5mm, and roughness height k=695μm, around the smooth inner cylinder of the Twente Turbulent Taylor–Couette facility. Between two sandpaper bands, the inner cylinder is left uncovered over similar width s, resulting

The fluid dynamics in the far-field of liquid sprays involves a wide range of spatio-temporal scales; challenging experimental observation and numerical modeling alike. Here we show how a combination of multiple imaging approaches, targeted to different scales, can provide useful insight into this class of flows. We performed multi-scale imaging measurements in the far-field of an upward-facing liquid

Numerical modeling of secondary breakup in gas atomization of molten metals has been successfully performed by others to optimize the powder particle size distribution for various additive manufacturing techniques and metal alloys. The application of breakup analytical models has been tested and validated through experimental campaigns by several researchers. They have demonstrated the suitability

In this paper a generalized conservative phase field-lattice Boltzmann model is proposed for immiscible incompressible flows with any number of components. In this phase field model, the each phase field variable satisfies a generalized eikonal equation and the volume fraction constraint. By introducing a quadratic functional, the dynamics of phase field variables can be treated as a gradient flow

Heat and mass transfer in a bilayer system of viscous incompressible liquids with interfaces have been studied theoretically and experimentally. Thermocapillary convection and interface deformations have been induced by an intense thermal exposure on the free boundary due to the action of a laser beam. The evolution of the interfaces and liquid behavior have been experimentally investigated. The static

The purpose of the present study is to investigate the characteristics of interfacial waves on flooding phenomena in an inclined pipe. The effects of liquid velocity and contact angle on the waves at the onset of flooding are studied with a two-dimensional computational fluid dynamic model. Flooding in a 30° inclined pipe is observed by using the Volume of Fluid (VOF) method. It is found when the contact

The smallest hydrodynamic length scales in two-phase turbulence are located at the interface between phases, or fluids, as a result of two-way coupling phenomena. Typically, these interface-generated scales are several times smaller than the dissipative scales in the surrounding bulk flow identified by Kolmogorov’s 1941 theory. Consequently, to properly capture these interface-generated small scales

The process of a circular free falling jet entering an idle pool was studied with the objective of determining a relation between the naturally occurring disturbances on the jet surface and air entrainment. To this end the instabilities of the free falling jet were characterized and compared with the bubble count distribution and an estimated amount of entrained air in the plume. Different jet lengths

Erosion, entrainment and deposition are complex and dominant, but yet poorly understood, mechanical processes in geophysical mass flows. Here, we propose a novel and process-based two-phase erosion-deposition model capable of adequately describing these complex phenomena commonly observed in landslides, avalanches, debris flows and bedload transports. The model is based on the jump in the momentum

Numerical difficulties, notably the non-monotonic behavior of the Wood speed of sound and the volume fraction positivity, associated with the reduced five-equation two-phase flow model of Kapila et al. (2001) [A.K. Kapila, R. Menikoff, J.B. Bdzil, S.F. Son, D.S. Stewart, 2001. Two-phase modeling of deflagration-to-detonation transition in granular materials: reduced equations, Physics of Fluids 13(10)

The evolution of two-phase flow patterns is investigated experimentally in a 1500 mm long capillary tube of 3 mm inner diameter with different orientations with respect to gravity. The flow patterns are recorded with a fast camera (1000 fps) at two locations along the tube under the same operating conditions. The first is close to the inlet zone at L/D = 10 and the second is far downstream at L/D = 420

Inductively-heated solid particles dispersed within a decaying isotropic turbulent carrier gas are investigated via Direct Numerical Simulations (DNS). The multiphase simulations account for the compressibility and temperature-dependent viscosity effects of the carrier gas. We develop a semi-empirical model for solid particle heating through hysteresis and Joules mechanisms as these dispersed particles

The present study seeks to conduct numerical investigations of the cavitating flow characteristics around a sinusoidal wavy leading edge (WLE) 3-D hydrofoil underlying a NACA 634–021 profile with an aspect ratio of 4.3. Cavitational and non-cavitational characteristics of hydrofoils are numerically examined at a chord-based Reynolds number of 7.2 × 105. The sinusoidal leading edge geometries include

The liquid-film flow in a vertical, upward, two-phase annular flow of saturated R245fa is characterized experimentally under adiabatic conditions. The experiments are conducted inside a rectangular channel with a cross section of 11.6 × 36 mm2 for mass velocities ranging from 95 to 130 kg/m2s, vapor qualities from 0.63 to 0.9 and saturation temperature of 23 °C. Liquid-film thickness and disturbance-wave

A turbulent duct flow laden with small heavy inertial particles (Reτ ≈ 570, St+≈50, dp+≈0.3, St ≈ 12, and dp/η ≈ 0.17) is studied computationally and experimentally. We examine whether a long development section can be modeled using a short periodic domain. This simplification is not valid if the development section is too short (less than 25–50 duct-height in our case), the periodic simulation is

Pressure drops in horizontally aligned U-bends were measured for air-water bubbly, plug, slug and annular flows to examine the applicability of available correlations to the data. The bend disturbed the flow and induced large pressure drops not only within the bend but also in the downstream-side straight pipe. The bend pressure drop was therefore evaluated as the sum of the pressure drop caused within

In theoretical analyses of the moving contact line, an infinite force along the solid wall has been reported based off the non-integrable stress along a single interface. In this investigation we demonstrate that the stress singularity is integrable and results in a finite force at the moving contact line if the contact line is treated as a one-dimensional manifold and all three interfaces that make

The role of mean shear on the orientational behavior of aspherical particles is studied by Lagrangian tracking of inertial spheroids in a directly simulated turbulent Couette–Poiseuille flow. The effects of particle inertia and shape in the conventional wall-turbulence near the stationary wall closely resemble observations made earlier in turbulent channel flows. The particles’ orientational behavior

In this paper, we present a detailed example of numerical study of the film formation in the context of metal coating. Subsequently we simulate wiping of the film by a planar jet. The simulations have been performed using Basilisk, a grid-adapting, strongly optimized code. Mesh adaptation allows for arbitrary precision in relevant regions such as the contact line or the liquid-air impact zone, while

Complex bubble breakup in turbulence has been studied and modeled extensively by employing the population balance equation. This equation hinges on two quantities, i.e. daughter bubble size distribution and breakup frequency. Since there is no first-principle equation that can be solved to calculate these two quantities, many phenomenological models based on different physical mechanisms have been

The linear stability of stratified two-phase flows in rectangular ducts is studied numerically. The linear stability analysis takes into account all possible infinitesimal three-dimensional disturbances and is carried out by solution of the associated eigenproblem. The neutral stability boundary and the corresponding critical wave number are obtained for liquid – liquid and air – water systems. Depending

Liquid–liquid dispersion by head-on impingement in a cross-slot microfluidic device to form oil-in-water emulsion is experimentally investigated at broad range of flow rate conditions. Reynolds number based on the continuous aqueous phase flow is changed from 1000 to 7000 and the oil dispersed volume fraction varies between 3% and 30%. The flow patterns are observed in the vicinity of impinging region

The present paper applied experimental and numerical methods to investigate the cavitating flow structures and corresponding hydrodynamics for a transient pitching Clark-Y hydrofoil. The aims are to (1) improve the understanding of the interplay between the transient cavitating flow structures, motion of the hydrofoil, and hydrodynamic performance, (2) quantify the influence of cavitation on the hydrodynamic

Optical experiments were used to identify breakup regimes for a liquid jet injected into in a second immiscible liquid undergoing turbulent Taylor vortex flow. Four jetting breakup behaviors were observed and these were compared with analogous jetting regimes in quiescent liquid-liquid systems as well as liquid-gas systems with a gaseous crossflow. Several jet breakage regime maps for liquid–liquid