Droplet Weber Number Research Articles

Investigation in the bag breakup of water droplet in airflow with different temperatures and densities

This paper tries to clarify the respective significance of thermal effects and airflow density on the influence of bag breakup of water droplets in hot airflow. The bag breakup processes of water droplets in the airflow temperature range of 293 K (ρg=1.205 kg/m3) to 493 K (ρg=0.716 kg/m3) were investigated. Meanwhile, room-temperature gas mixtures with corresponding densities were prepared using room-temperature helium blended with room-temperature air to explore the bag breakup processes of water droplets. The results show that although the critical conventional Weber number (Wecon) of spherical droplets for bag breakup varies significantly in both streams, the critical initiation Weber number (Weini) of disk-shaped droplets for bag breakup remains almost consistent. Different deformation processes from Wecon to Weini result in different Wecon. In the gas mixtures with room temperature, the critical Wecon for bag breakup increases from 9.47 to 12.12 as the stream density decreases from 1.205 to 0.716 kg/m3. However, the critical Wecon for bag breakup decreases from 9.47 to 7.80 in the hot airflow at identical airflow density variations.

Impact regimes of a single water droplet impacting a hot immiscible liquid surface

This paper studied the dynamic interaction process of a single water droplet impinging onto an immiscible target liquid, which was a follow-up study on a single water droplet impacting a miscible target liquid i.e. ethanol. Heptane was chosen as the impacted liquid, and the water droplet with a fixed diameter of 1.98 mm was used in the experiments. The droplet Weber number ranged from 30 to 762 by changing the height between the droplet and the impacted liquid surface. A high-speed digital camera at a speed of 2000 fps was used to capture the dynamic process. A comprehensive map We∼θ of typical impact phenomena including penetration, splashing, and bubble was plotted, considering both the cases of immiscible and miscible liquids. The critical Weber numbers of forming the typical phenomena were deduced. The critical Weber numbers for the transition from penetration to splashing and the transition from splashing to bubble could be approximately predicted by We=824.3−140.9e1.5θ and We=62.1+61.5θ, respectively. To clarify the formation mechanisms of typical phenomena, the energy conversions during the dynamic process were analyzed. The influences of pool temperature on energy conversion rates of the crater and jet formation could be predicted by χ=0.437θ+0.156 and φ=0.245θ+0.072, respectively.

Prince Rupert's Drop bouncing on high-speed moving superhydrophobic surfaces

Superhydrophobic surfaces have shown huge potential in diverse fields. However, the hydrodynamics of droplet impacting on moving superhydrophobic surfaces are largely unexplored, especially for surfaces with a high moving velocity. The knowledge gap in liquid-solid interaction between impacting droplets and high-speed moving superhydrophobic surfaces should be filled to better guide practical engineering applications. Here, a superhydrophobic surface is fabricated as the experimental surface by a chemical deposition-etching method and droplet impacting experiments on horizontally moving superhydrophobic surfaces (realized by impacting the edge of a rotating surface) are systematically conducted. The moving velocity of superhydrophobic surfaces reaches nearly 10.0 m/s, which is approximately three times the velocity in previous relevant studies. The results show that the droplet spreading is greatly enhanced when the surface velocity exceeds a critical value, and it is independent of the droplet Weber number (We). The droplet detaches from the surface in the shape of “Prince Rupert's Drop”, reducing the contact time by over 40%. The critical surface velocity is characterized by We/Wes = 0.17, where Wes is the Weber number of the moving surface. To reveal the dynamics of Prince Rupert's Drop bouncing, scaling laws of the maximum spreading coefficient and the contact time are developed, which agree well with experimental results.

Impingement of a water droplet onto a water film on the surface with micro-structures

In the present study, we carried out an experimental investigation of the impacting process of a water droplet onto a water film on the surface with micro-structures. A parameter study of the droplet Weber number, the dimensionless water film thickness, and the dimensionless distance between two micro-protrusions was carefully performed. In addition, the impacting process of a water droplet onto a water film on the flat surface was also measured for comparisons. The results showed that, within the scope of this study, the increase of the dimensionless distance between two protrusions had a minor effect on the crown top diameter evolution and the crown lifetime. In addition, the number of secondary droplets was not monotonously affected by the increase of the dimensionless distance between two protrusions. Under the same droplet Weber number condition, when the water film was relatively thin, the dimensionless distance between two protrusions was found to have apparent influence on the evolution of crown base diameter. Besides, considering the effect of the dimensionless distance between two protrusions, we proposed a modified energy loss factor as well as two correlations for the maximum dimensionless crown height and the time to reach the maximum height.

Experimental study on the droplet dynamics after impacting an inclined superhydrophobic surface

Super-hydrophobic surface has been widely studied, related to surface self-cleaning and liquid transport. In this study, effects of the inclined angle and impact velocity on the dynamic characteristics of droplet impact are experimentally investigated, using high-speed photography. When the spreading break-up does not occur, the effect of the inclined angle on the maximum spreading diameter is mainly determined by the competition between the decrease in the inertial force component normal to the surface and the increase in the gravity and inertial force component parallel to the surface. A formula has been developed to predict the maximum spreading factor under different inclined angles. The increasing inclined angle promotes the complete rebound. When the impact velocity is constant, there exists a critical inclined angle, at which the rebounding time is minimum. Furthermore, the critical inclined angle increases with the impact velocity. The increasing inclined angle can affect droplet ejection and potentially hinder its occurrence. Droplet ejection is classified into five stages based on the change in the ratio of the ejected to initial droplet diameter versus Weber number normal to the surface. For stage 5, an empirical formula that predicts the diameter of ejected droplets under different inclined angles is given out. This study can provide a novel idea for the generation and transport of microdroplets of directed size, as well as the recycling of the remaining liquid film after droplet ejection.

Experimental investigation of oil film flow and droplets behavior in the annular channel of a cyclone separator

The separation of the gas and liquid in the gas-liquid cyclone separator is achieved through the swirling flow. The liquid film flow characteristics and the dynamics of droplets impacting the liquid film are very important for the separation performance, but these phenomena have not been well understood in the swirling flow. In this work, an experiment was conducted to investigate the liquid film flow and droplet impingement in the annular channel of the gas-liquid cyclone separator. Three regions of the annular channel could be divided based on the film flow patterns, which were the inlet region, the annular region, and the outlet region; and four typical droplet impact outcomes could be observed, which were splashing, coalescence, bouncing, and jet breakup. According to the characteristics of the liquid film and the outcome of droplet liquid film impingement, if the droplet splashing in the inlet region could be weakened and the length of the annular region was lengthened, it would be beneficial for gas-liquid separation. The impact outcomes were shown to undergo a transition from bouncing to coalescence as the droplet Weber number increased. Droplet coalescence was affected by the disturbance of gas flow and the evenness of the liquid film, so when the superficial velocity of the gas flow was fixed, the transition boundary was constant whatever the liquid volume fraction in the channel, and when the Reynolds number of the gas flow increased, the transition boundary of droplet Weber number increased first and then decreased. This work may provide a basis for a comprehensive understanding of the liquid film flow pattern and droplet behavior in the cyclone separator, and the results have the potential to be applied in other multiphase studies.

Time-resolved low-pressure air-assisted spray performance and unsteadiness evaluation

The main advantages of air-assisted spray are its high-quality atomization at low injection pressures and insensitivity to the viscosity of atomized liquid. In this study, the droplet size and velocity of a low-pressure intermittent air-assisted spray were studied by using phase Doppler anemometry, and the effects of liquid fuel injection duration on time-resolved spray microscopic characteristics and spray unsteadiness were analyzed. Droplet size-velocity joint probability density functions were employed to characterize the droplet diameter-velocity distribution as well as the probability range. A comparison of the droplet Weber number with an empirical critical value indicates that atomized droplets hardly undergo secondary shear breakup. Based on the ideal spray theory of Edwards and Marx, an improved algorithm is proposed with the concept of iterative rejection of inter-particle arrival times to quantify the unsteadiness of air-assisted sprays by eliminating the dependence of the calculation results on droplet sampling data. The results show that intermittent air-assisted spray is an inherently unsteady process that can be influenced by fuel injection duration and spatial location, while independent of the droplet size. In addition, the spray unsteadiness exhibits noteworthy variations at different spray stages segmented by droplet velocity vs time. The relation between the potential internal gas–liquid two-phase status determined by fuel injection duration and the spray performance is elaborated.

Experimental and Numerical Study of Droplet Impact on Radially Flowing Liquid Film

In this paper, a single droplet impact onto a radially flowing liquid film is investigated both experimentally and numerically. The interfacial evolution and dynamic features are studied in detail with regard to various droplet impact velocities and film flow rates. Also, the corresponding mechanisms are analyzed with the aid of numerical results using the coupled level set and volume of fluid method. Results show that the droplet impact on the radial film produces a larger crown radius in the direction perpendicular to the film flow compared with the unidirectional film. Increasing the impact velocity leads to increases in crown height and upstream radius, but it has a weak effect on the downstream radius. As for the effect of the film flow rate, its increase causes a rise in the secondary droplet number in the upstream but makes the finger jets associated with the crown splashing less developed. Besides, increasing the flow rate of the liquid film results in increases in the upstream crown height and downstream radius but decreases in the downstream crown height and upstream radius. Finally, a formula for predicting the threshold of splashing is built up based on the film flow Reynolds number and the droplet Weber number.

Analysis of the breaking process and the components of the crown structure after a single droplet hits thin liquid film

• Three types of crown breakup: splash breaking, hole breaking, and mixed breaking. • Fluid film viscosity and droplet Weber number affect the crown breakup. • Empirical correlations to classify three types of crown breakup was proposed. The breaking process and the components of the crown formed when the single droplet impact on different liquid films were investigated experimentally and simulatly. Laser-induced fluorescence (LIF) methods were used to study the breakup process of the crown structure. The composition of the incident droplets in this test is ethanol, and the glycerol aqueous solution was used as the liquid film. Results show that at different droplet Weber numbers, liquid film thickness, and liquid film viscosity, it is reasonable to classify the breakup of crown structure into the following three regimes: splash breaking, hole breaking, and mixed breaking. The characteristics of each breaking regime, such as the breaking mechanism, diameter of crown structure and spatial distribution of the secondary droplets formed after breakup, have been qualitatively analyzed. The viscosity of the liquid film and the Weber number of incident droplets have significant influence on the breakup of the crown structure. With decreasing viscosity and increasing Weber number, the crown structure breaking process transits from unbroken to splash breaking, hole breaking, and finally mixed breaking. According to the experimental results, a fitting formula for describing critical parameters of the different breaking regimes of crown structure is established. To further quantify the material components of the crown structure and the mixing of the incident droplets with the liquid film, Volume of Fluid (VOF) model and species transport model were used to establish a model for simulation calculations, and the effects of droplet Weber number, liquid film thickness and liquid film viscosity were clarified.

Spray characterization in a multi-jet airblast injector with swirling air crossflow

Experimental spray characterization in a multi-jet airblast injector with swirling crossflow of air is the goal of the present work. The current injector allows radial injection of six liquid jets from a central hub into swirling and crossflowing air into the annular region around the hub. In the present study, three different aspects related to jet-in-crossflow are concurrently addressed viz. air flow confinement, air swirl and simultaneous atomization of multiple liquid jets. Such key features have been rarely reported in the past in spite of their relevance to practical injectors such as in Lean Premixed Prevaporized (LPP) gas turbine combustors. The spray structure and spatial distribution of droplets are visualized at different cross-sectional planes in the spray by application of the Laser Sheet Imaging (LSI) technique. The Droplet size, three components of droplet velocities and local liquid mass flux are measured at different axial and radial locations using the Phase Doppler Particle Analyzer (PDPA) technique. The injector is operated over a wide range of aerodynamic Weber number (Weg) of the liquid jets (Weg = 57 – 430). The physics behind the spatial evolution of characteristic droplet size is analyzed by estimating the droplet Weber number and the probability of droplet coalescence. The plume-to-plume interaction, subsequent to droplet generation from the primary atomization of adjacent liquid jets, is found to contribute to the variation of droplet size in the current injector. The influence of Weg on the evolution of spray characteristics is investigated in detail.

Primary atomization of liquid jets: Identification and investigation of droplets at the instant of their formation using direct numerical simulation

A detailed investigation of droplet characteristics for the primary atomization of a round liquid jet injected into stagnant gas is performed using direct numerical simulation. The material properties correspond to a Diesel injection, and the numerical framework is based on the volume-of-fluid method. The study is carried out in the statistically steady state, which allows to collect time-averaged droplet formation statistics. A novel algorithm continuously detects droplets at the instant they detach from the liquid core jet, which are referred to as primary droplets. The main droplet characteristics, such as volume, velocity and sphericity, are captured for newly formed primary droplets as well as all other droplets in the domain. This allows a detailed comparison between droplet characteristics during and after their formation. In addition, the droplet Weber, Reynolds and Stokes numbers are computed. These dimensionless numbers govern important physical processes occurring subsequent to the droplet formation, such as potential secondary breakup and droplet motion. One central goal is to provide information relevant for large eddy simulation of sprays in the Eulerian–Lagrangian framework, where the formation of small droplets from the liquid core jet cannot be resolved, and therefore potentially needs to be modeled. Moreover, the relative importance of primary and secondary atomization is estimated for this specific setup. It is found that the distribution of the droplet sizes is very similar for primary droplets and the entire droplet collective. Furthermore, the droplet Weber numbers are significantly below the critical Weber number required for secondary droplet breakup. Together, these two observations indicate that, for the investigated configuration, primary atomization is the dominating process, while secondary atomization only plays a minor role. Moreover, the high droplet volume fraction observed shows that droplet–droplet collisions and coalescence can be expected to influence the spray behavior. To put the obtained results into perspective, empirical correlations for the Sauter Mean Diameter are used to discuss potential trends for higher Reynolds and Weber numbers.

Physical mechanisms for droplet size and effective viscosity asymmetries in turbulent emulsions

By varying the oil volume fraction, the microscopic droplet size and the macroscopic rheology of emulsions are investigated in a Taylor–Couette turbulent shear flow. Although here oil and water in the emulsions have almost the same physical properties (density and viscosity), unexpectedly, we find that oil-in-water (O/W) and water-in-oil (W/O) emulsions have very distinct hydrodynamic behaviours, i.e. the system is clearly asymmetric. By looking at the micro-scales, the average droplet diameter hardly changes with the oil volume fraction for O/W or for W/O. However, for W/O it is about $50\,\%$ larger than that of O/W. At the macro-scales, the effective viscosity of O/W is higher when compared to that of W/O. These asymmetric behaviours are expected to be caused by the presence of surface-active contaminants from the walls of the system. By introducing an oil-soluble surfactant at high concentration, remarkably, we recover the symmetry (droplet size and effective viscosity) between O/W and W/O emulsions. Based on this, we suggest a possible mechanism responsible for the initial asymmetry and reach conclusions on emulsions where interfaces are fully covered by the surfactant. Next, we discuss what sets the droplet size in turbulent emulsions. We uncover a $-6/5$ scaling dependence of the droplet size on the Reynolds number of the flow. Combining the scaling dependence and the droplet Weber number, we conclude that the droplet fragmentation, which determines the droplet size, occurs within the boundary layer and is controlled by the dynamic pressure caused by the gradient of the mean flow, as proposed by Levich (Physicochemical Hydrodynamics, Prentice-Hall, 1962), instead of the dynamic pressure due to turbulent fluctuations, as proposed by Kolmogorov (Dokl. Akad. Nauk. SSSR, vol. 66, 1949, pp. 825–828). The present findings provide an understanding of both the microscopic droplet formation and the macroscopic rheological behaviours in dynamic emulsification, and connects them.

Wettability and water‐droplet contact electrification of nanostructural polypropylene (PP) by plasma modification

AbstractThe superhydrophobic surfaces with three kinds of nanopillars on polypropylene (PP) substrates are fabricated by a plasma nanotexturing technique comprising oxygen‐plasma treatment (OPT) followed by fluorocarbon polymer deposition (FPD). The diameters of nanopillars and spacing distances between nanopillars are tuned under the different OPT and FPD duration times. The wettability and contact electrification on the surfaces are analyzed under the water droplet impact by changing the impacting droplet number, Weber number, and salt concentration. The dense or wide nanopillars favor high contact charge on the surfaces with nanopillars, arousing the damage of the superhydrophobicity with low adhesion. The low contact charge impacting the droplets with high salt concentration has a weakened effect on the superhydrophobicity of the surfaces with nanopillars.

Speed of fragments ejected by an expanding liquid tin sheet

We experimentally investigate the speed of fragments produced by ligament breakup in laser-induced deformation of tin microdroplets into axisymmetric sheets. A double-frame backlit camera is used to obtain the speed of the fragments and the time of their detachment. We show that by normalizing these speeds to the initial expansion speed of the sheet, all data collapse onto a single universal curve that is a function of the dimensionless time ${t}_{d}/{\ensuremath{\tau}}_{c}$ only, where ${\ensuremath{\tau}}_{c}$ is the capillary time. We further find that this universal curve is explicitly independent of the droplet's Weber number.

Transient boiling heat transfer mechanism of droplet impacting heated cylinder

The spray on the heated cylindrical surface for boiling widely exists in the industrial application. In order to discover the transient boiling heat transfer mechanism, the cases of droplet impacting on the cylindrical surface were experimentally carried out. In this experiment, the droplet hydrodynamics were captured by high-speed camera. The effects of impact velocity and wall temperature on the hydrodynamics and boiling heat transfer performance were studied in detail. The results show that, for the droplet impacting on the heated cylindrical surface, four types of phase change heat transfer regimes, i.e., film evaporation regime, nucleate boiling regime, transition boiling regime and film boiling regime are found. From the built map of relationship between wall temperature and Weber number, it is demonstrated that when the wall superheat is low, increasing the droplet impact velocity enlarges the solid-liquid contact area, boosting the heat transfer performance in the film evaporation and nucleate boiling regimes. However, when the wall superheat is high, increasing the droplet impact velocity or Weber number makes the Leidenfrost point be lower and is unfavorable for heat transfer due to the easy generation of vapor layer, which strongly differs from the conclusion of droplet impacting on the heated flat surface according to others’ investigations. The underlying mechanism can be revealed from two aspects, i.e., the formation mechanism of Leidenfrost state and the effect of surface geometry. Finally, the quantitative relationship between Leidenfrost point and Weber number is given.

Experimental study on spreading and splashing behavior of continuous droplets impacting on heated wall

Continuous droplets impingement on the wall is common in industry and widely adopted in the fields of power machinery, materials science, agriculture, chemical industry and so on. In this work, the spreading and splashing behavior of continuous droplets impinging on the heated wall at Jacob numbers (Ja) and with different droplet Weber numbers (Wed) (Ja = -0.054 to 0.270, Wed = 30–1000) are studied experimentally. By means of the high-speed photography, the continuous droplets impacting on the heated wall produced by the ceramic piezoelectric droplet generator was observed. Next, the behaviors of the droplet impact on the wall under different conditions are divided into spreading, bouncing, coronal spatter and complete spatter, and the phase diagrams of droplet spreading are presented. In addition, the spreading and splashing factors are determined according to the experimental image of the droplet spreading. The analysis and mathematical fittings are carried out for the variation of spreading parameters of droplet with different Wed number and Ja number. Additionally, secondary droplets produced by the droplet splashing under different experimental conditions were observed, and the relationship between droplet splashing parameters, Wed number and Ja number were analyzed and modeled.

Non-simultaneous droplet impingement cooling of a solid heated surface

High generation of heat in the electronics industry presents a roadblock for further innovations in higher processing power due to complications associated with overheating. Commonly used air-based systems cannot cool high-performance electronics, mainly due to the relatively poor thermo-physical properties of air. Spray cooling is a technique capable of cooling or quenching objects at very high temperatures and heat fluxes. While there has been considerable research on single droplet impact to study the fundamentals of spray cooling, multiple droplet impingement offers more realistic realisations of the dynamics of spray phenomena. In this paper, we examined the fluid dynamics and heat transfer of multiple droplet impingement using high-speed imaging and fast heat flux measurements to capture droplet-droplet and droplet-surface interactions at constant droplet Weber number. We investigated an individual droplet and two non-simultaneous droplets of water at a constant horizontal droplet spacing and different time separations to analyse the heat transfer at different initial surface temperatures. Although not affected significantly by the surface temperature, the maximum diameter of the combined droplets decreased for increasing time separation due to the kinematic discontinuity from the interaction between droplets moving in opposite direction. For small time separation, the spreading droplet contact line of the first droplet collided with the moving contact line of the second droplet. The receding and the quasi-static contact lines of the first droplet was strongly and mildly impacted by the second spreading droplet diameter, respectively. However, all quasi-static droplet diameters increased for non-simultaneous droplet scenario, following by a small reduction in the droplet diameter when the surface temperature increased due to evaporation. Depending on the surface temperature and time separation between droplets, it was found that the peak heat transfer rates for non-simultaneous droplet impingement scenarios can be increased by 68% to 100% when compared to a single droplet case due to higher combined droplet diameter and fluid volume in contact with the heated solid surface. However, the overall droplet cooling efficiency was higher for the single droplet case, showing that the droplet-droplet interaction can decrease the potential cooling performance of droplets. The present study provides knowledge combining droplet-droplet interaction and heat transfer performance for future spray cooling system design and optimisation.

On the Vaporization Rate and Flame Shape of Nonspherical Droplets

Abstract Motivated by the study of spray combustion, this work addresses the combustion of nonspherical droplets. The combustion of spray is usually understood through the theory of droplet combustion, and improving this latter theory is the narrow aim of this work. This work uses perturbation theory to derive a novel model for the vaporization of nonspherical droplets. Compared to previous efforts in this area, the work uses a physics-based approach by incorporating ideas from the asymptotic analysis of Taylor and Acrivos (1964, “On the Deformation and Drag of a Falling Viscous Drop at Low Reynolds Number,” J. Fluid Mech. 18(3), pp. 466–476). The perturbation strategy expands the droplet shape using spherical harmonics, and the theory characterizes the shape of the droplet via the Weber number. The introduction of this parameter is key as it is a parameter that can be easily measured in experiments, and thus it can be used to connect the theoretical results with application. The perturbation analysis is performed based around the classical solution of spherical droplet combustion in quiescent flow. The theory indicates that the effect of droplet deformation can be accounted for by a correction to the droplet combustion rate that is a simple polynomial function of the droplet Weber number. Results are compared to existing literature, and it confirms the established trend that deformed droplets vaporize faster than spherical droplets. Analysis of the flame shape reveals that the flame remains nearly spherical; however, the mean flame standoff changes with droplet shape. The extension of the theory to high Reynolds number conditions is briefly discussed.

Liquid Droplet Impact Over Hydrophobic Mesh Surfaces and Assessment of Weber Number Dependent Characteristics

Abstract Impacting droplets and droplet ejection from hydrophobic mesh surfaces have interest in biomedicine, heat transfer engineering, and self-cleaning of surfaces. The rate and the size of newborn droplets can vary depending on the droplet fluid properties, Weber number, mesh geometry, and surface wetting states. In this study, impacting water droplets onto hydrophobic mesh surface is investigated and impact properties including, spreading, rebounding, and droplet fluid penetration and ejection rates are examined. Droplet behavior is assessed using high recording facilities and predicted in line with the experiments. The findings reveal that the critical Weber number for droplet fluid penetrating/ejecting from mesh screen mainly depends on the droplet fluid capillary length, and hydrophobic mesh size. The contact time of impacting droplet over mesh surface reduces with increasing droplet Weber number, which opposes the case observed for impacting droplets over flat hydrophobic surfaces. The restitution coefficient attains lower values for impacting droplets over mesh surfaces than that of flat surfaces. The rate and diameter of the ejected droplet from the mesh increases as droplet Weber increases. At the onset of impact, streamline curvature is formed inside droplet fluid, which creates a stagnation zone with radially varying pressure at the droplet fluid mesh interface. This reduces the ejected droplet diameter from mesh cells as mesh cells are located away from the impacting vertical axis.

Modeling partition coefficient of liquid droplets impacting on particles by direct numerical simulation

Liquid partition coefficient, defined as the proportion of the liquid volume covered on particle surface to that in bulk phase, is a key parameter in the simulation of liquid-injected fluidized beds. To develop the sub-grid model for liquid partition coefficient as a function of local hydrodynamics, a two-dimensional Volume-of-Fluid (VOF) simulation was conducted to directly resolve droplets impinging, wetting and spreading on particles in a box. The model was first validated by the experiments in literature on the spreading diameter of a droplet impinging on a single particle. Then for a system of multiple droplets-particles impinging, we investigated the effects of Weber number, droplet-to-particle (DTP) ratio and particle volume fraction on several characteristic parameters, e.g., ratio of liquid area adhered to particles to the total liquid area, liquid film thickness, the percentage of wetted particle surface area and liquid holdup. All these parameters decrease with increasing Weber number when We = 10 ∼ 370, and then gradually stabilize. Higher particle volume fraction increases the collisional frequency of droplets and particles, and therefore the ratio of liquid area adhered to particles to the total liquid area. By contrast, DTP is not the dominant factor in liquid partition. Finally a correlation for liquid partition coefficient is proposed as a function of droplet Weber number and particle volume fraction. It may serve as a sub-grid model for CFD-DEM or multifluid models in simulation of large-scale liquid-injected fluidized beds.