Engineering › Computational Mechanics

Fluid Dynamics and Heat Transfer

Works Count: 32068

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Description

This cluster of papers focuses on the dynamics of drop impact on surfaces, including phenomena such as drop splashing, spreading, and coalescence. It explores topics related to surface tension, multiphase flow, level set methods, spray cooling, and the Leidenfrost phenomenon.

Keywords

Drop Impact; Surface Tension; Fluid Dynamics; Multiphase Flow; Level Set Method; Spray Cooling; Interface Reconstruction; Liquid Jet Instability; Coalescence of Drops; Leidenfrost Phenomenon

A Spray/Wall Interaction Submodel for the KIVA-3 Wall Film Model

2000-03-06

P.J. O’Rourke , A.A. Amsden

Controlling droplet deposition with polymer additives

2000-06-01

Vance Bergeron , Daniel Bonn , Jean Yves Martin +1 more

Drop Splashing on a Dry Smooth Surface

2005-05-11

Lei Xu , Wendy W. Zhang , Sidney R. Nagel

The corona splash due to the impact of a liquid drop on a smooth dry substrate is investigated with high-speed photography. A striking phenomenon is observed: splashing can be completely … The corona splash due to the impact of a liquid drop on a smooth dry substrate is investigated with high-speed photography. A striking phenomenon is observed: splashing can be completely suppressed by decreasing the pressure of the surrounding gas. The threshold pressure where a splash first occurs is measured as a function of the impact velocity and found to scale with the molecular weight of the gas and the viscosity of the liquid. Both experimental scaling relations support a model in which compressible effects in the gas are responsible for splashing in liquid solid impacts.

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The aerodynamic instability and disintegration of viscous liquid sheets

1963-03-01

N. Dombrowski , William Johns

Evaluating the performance of the two-phase flow solver interFoam

2012-11-09

Suraj Deshpande , Lakshman Anumolu , Mario F. Trujillo

The performance of the open source multiphase flow solver, interFoam, is evaluated in this work. The solver is based on a modified volume of fluid (VoF) approach, which incorporates an … The performance of the open source multiphase flow solver, interFoam, is evaluated in this work. The solver is based on a modified volume of fluid (VoF) approach, which incorporates an interfacial compression flux term to mitigate the effects of numerical smearing of the interface. It forms a part of the C + + libraries and utilities of OpenFOAM and is gaining popularity in the multiphase flow research community. However, to the best of our knowledge, the evaluation of this solver is confined to the validation tests of specific interest to the users of the code and the extent of its applicability to a wide range of multiphase flow situations remains to be explored. In this work, we have performed a thorough investigation of the solver performance using a variety of verification and validation test cases, which include (i) verification tests for pure advection (kinematics), (ii) dynamics in the high Weber number limit and (iii) dynamics of surface tension-dominated flows. With respect to (i), the kinematics tests show that the performance of interFoam is generally comparable with the recent algebraic VoF algorithms; however, it is noticeably worse than the geometric reconstruction schemes. For (ii), the simulations of inertia-dominated flows with large density ratios yielded excellent agreement with analytical and experimental results. In regime (iii), where surface tension is important, consistency of pressure–surface tension formulation and accuracy of curvature are important, as established by Francois et al (2006 J. Comput. Phys. 213 141–73). Several verification tests were performed along these lines and the main findings are: (a) the algorithm of interFoam ensures a consistent formulation of pressure and surface tension; (b) the curvatures computed by the solver converge to a value slightly (10%) different from the analytical value and a scope for improvement exists in this respect. To reduce the disruptive effects of spurious currents, we followed the analysis of Galusinski and Vigneaux (2008 J. Comput. Phys. 227 6140–64) and arrived at the following criterion for stable capillary simulations for interFoam: where . Finally, some capillary flows relevant to atomization were simulated, resulting in good agreement with the results from the literature.

Droplet-wall collisions: Experimental studies of the deformation and breakup process

1995-04-01

Chr. Mundo , Martin Sommerfeld , Cameron Tropea

Mechanism of atomization of a liquid jet

1982-10-01

Rolf D. Reitz , F. V. Bracco

In the atomization regime of a round liquid jet, a diverging spray is observed immediately at the nozzle exit. The mechanism that controls atomization has not yet been determined even … In the atomization regime of a round liquid jet, a diverging spray is observed immediately at the nozzle exit. The mechanism that controls atomization has not yet been determined even though several have been proposed. Experiments are reported with constant liquid pressures from 500 psia (33 atm) to 2500 psia (166 atm) with five different mixtures of water and glycerol into nitrogen, helium, and xenon with gas pressures up to 600 psia (40 atm) at room temperature. Fourteen nozzles were used with length-to-diameter ratios ranging from 85 to 0.5 with sharp and rounded inlets, each with an exit diameter of about 340 μm. An evaluation of proposed jet atomization theories shows that aerodynamic effects, liquid turbulence, jet velocity profile rearrangement effects, and liquid supply pressure oscillations each cannot alone explain the experimental results. However, a mechanism that combines liquid–gas aerodynamic interaction with nozzle geometry effects would be compatible with our measurements but the specific process by which the nozzle geometry influences atomization remains to be identified.

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Time evolution of liquid drop impact onto solid, dry surfaces

2002-07-01

Romain Rioboo , Marco Marengo , Cameron Tropea

An Adaptive Level Set Approach for Incompressible Two-Phase Flows

1999-01-01

Mark Sussman , Ann Almgren , John B. Bell +3 more

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Volume-of-Fluid Interface Tracking with Smoothed Surface Stress Methods for Three-Dimensional Flows

1999-07-01

Denis Gueyffier , Jie Li , Ali Nadim +2 more

A front-tracking method for viscous, incompressible, multi-fluid flows

1992-05-01

Salih Özen Ünverdi , Grétar Tryggvason

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The Particle-Source-In Cell (PSI-CELL) Model for Gas-Droplet Flows

1977-06-01

C. T. Crowe , M. P. Sharma , David E. Stock

The analysis of gas-droplet flows is complicated by the need to account for the mass, momentum, and energy coupling between phases. The concept of regarding the droplet phase as a … The analysis of gas-droplet flows is complicated by the need to account for the mass, momentum, and energy coupling between phases. The concept of regarding the droplet phase as a source of mass, momentum, and energy to the gaseous phase is described and incorporated into a computational model. A steady two-dimensional spray-cooling problem is analyzed to illustrate the applicability of the model. The predicted temperature and velocity flow field for the gas and droplet phase aptly illustrate the capability of the model to treat the complex phenomena associated with multiphase flows.

Coalescence and separation in binary collisions of liquid drops

1990-12-01

Nasser Ashgriz , J. Y. Poo

An extensive experimental investigation of the binary collision dynamics of water drops for size ratios of 1. 0.75, and 0.5, for the Weber-number range of 1 to 100, and for … An extensive experimental investigation of the binary collision dynamics of water drops for size ratios of 1. 0.75, and 0.5, for the Weber-number range of 1 to 100, and for all impact parameters is reported. Two different types of separating collisions, namely reflexive and stretching separations, are identified. Reflexive separation is found to occur for near head-on collisions, while stretching separation occurs for large-impact-parameter collisions. The boundaries between both of the separating collisions and coalescence collision are found experimentally. Theoretical models for predictions of the reflexive and stretching separation are also given.

A Theoretical Study of the Liquid Bridge Forces between Two Rigid Spherical Bodies

1993-11-01

Guoping Lian , Colin Thornton , M.J. Adams

Capillary effects during droplet impact on a solid surface

1996-03-01

Mohammad Passandideh‐Fard , Yuhui Qiao , S. Chandra +1 more

Impact of water droplets on a flat, solid surface was studied using both experiments and numerical simulation. Liquid–solid contact angle was varied in experiments by adding traces of a surfactant … Impact of water droplets on a flat, solid surface was studied using both experiments and numerical simulation. Liquid–solid contact angle was varied in experiments by adding traces of a surfactant to water. Impacting droplets were photographed and liquid–solid contact diameters and contact angles were measured from photographs. A numerical solution of the Navier–Stokes equation using a modified SOLA-VOF method was used to model droplet deformation. Measured values of dynamic contact angles were used as a boundary condition for the numerical model. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces, after which they recoiled off the surface. Adding a surfactant did not affect droplet shape during the initial stages of impact, but did increase maximum spread diameter and reduce recoil height. Comparison of computer generated images of impacting droplets with photographs showed that the numerical model modeled droplet shape evolution correctly. Accurate predictions were obtained for droplet contact diameter during spreading and at equilibrium. The model overpredicted droplet contact diameters during recoil. Assuming that dynamic surface tension of surfactant solutions is constant, equaling that of pure water, gave predicted droplet shapes that best agreed with experimental observations. When the contact angle was assumed constant in the model, equal to the measured equilibrium value, predictions were less accurate. A simple analytical model was developed to predict maximum droplet diameter after impact. Model predictions agreed well with experimental measurements reported in the literature. Capillary effects were shown to be negligible during droplet impact when We≫Re1/2.

Volume of fluid (VOF) method for the dynamics of free boundaries

1981-01-01

C.W. Hirt , B.D. Nichols

A balanced-force algorithm for continuous and sharp interfacial surface tension models within a volume tracking framework

2005-09-20

Marianne Francois , Sharen J. Cummins , E. D. Dendy +3 more

An improved level set method for incompressible two-phase flows

1998-06-01

Mark Sussman , Emad Fatemi , Peter Smereka +1 more

A Coupled Level Set and Volume-of-Fluid Method for Computing 3D and Axisymmetric Incompressible Two-Phase Flows

2000-08-01

Mark Sussman , Elbridge Gerry Puckett

The impact of a single drop on a wetted solid surface

1997-04-01

Gianpietro Cossali , A. Coghe , Marco Marengo

Physics of liquid jets

2008-02-21

Jens Eggers , Emmanuel Villermaux

Jets, i.e. collimated streams of matter, occur from the microscale up to the large-scale structure of the universe. Our focus will be mostly on surface tension effects, which result from … Jets, i.e. collimated streams of matter, occur from the microscale up to the large-scale structure of the universe. Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids. Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology. Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup. In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology. They also arise from the last but one topology change of liquid masses bursting into sprays. Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium. The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects.

A Method for Capturing Sharp Fluid Interfaces on Arbitrary Meshes

1999-07-01

Onno Ubbink , R. I. Issa

A Level Set Approach for Computing Solutions to Incompressible Two-Phase Flow

1994-09-01

Mark Sussman , Peter Smereka , Stanley Osher

Second-order accurate volume-of-fluid algorithms for tracking material interfaces

2004-07-22

James Edward Pilliod , Elbridge Gerry Puckett

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An accurate adaptive solver for surface-tension-driven interfacial flows

2009-05-11

Stéphane Popinet

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Direct numerical simulations of gas/liquid multiphase flows

2006-06-07

Grétar Tryggvason , Asghar Esmaeeli , Jiacai Lu +1 more

Direct numerical simulations of bubbly flows are reviewed and recent progress is discussed. Simulations, of homogeneous bubble distribution in fully periodic domains at relatively low Reynolds numbers have already yielded … Direct numerical simulations of bubbly flows are reviewed and recent progress is discussed. Simulations, of homogeneous bubble distribution in fully periodic domains at relatively low Reynolds numbers have already yielded considerable insight into the dynamics of such flows. Many aspects of the evolution converge rapidly with the size of the systems and results for the rise velocity, the velocity fluctuations, as well as the average relative orientation of bubble pairs have been obtained. The challenge now is to examine bubbles at higher Reynolds numbers, bubbles in channels and confined geometry, and bubble interactions with turbulent flows. We briefly review numerical methods used for direct numerical simulations of multiphase flows, with a particular emphasis on methods that use the so-called "one-field" formulation of the governing equations, and then discuss studies of bubbles in periodic domains, along with recent work on wobbly bubbles, bubbles in laminar and turbulent channel flows, and bubble formation in boiling.

Drop impact onto a liquid layer of finite thickness: Dynamics of the cavity evolution

2009-03-18

Edin Berberović , Nils Paul van Hinsberg , Suad Jakirlić +2 more

In the present work experimental, numerical, and theoretical investigations of a normal drop impact onto a liquid film of finite thickness are presented. The dynamics of drop impact on liquid … In the present work experimental, numerical, and theoretical investigations of a normal drop impact onto a liquid film of finite thickness are presented. The dynamics of drop impact on liquid surfaces, the shape of the cavity, the formation and propagation of a capillary wave in the crater, and the residual film thickness on the rigid wall are determined and analyzed. The shape of the crater within the film and the uprising liquid sheet formed upon the impact are observed using a high-speed video system. The effects of various influencing parameters such as drop impact velocity, liquid film thickness and physical properties of the liquids, including viscosity and surface tension, on the time evolution of the crater formation are investigated. Complementary to experiments the direct numerical simulations of the phenomena are performed using an advanced free-surface capturing model based on a two-fluid formulation of the classical volume-of-fluid (VOF) model in the framework of the finite volume numerical method. In this model an additional convective term is introduced into the transport equation for phase fraction, contributing decisively to a sharper interface resolution. Furthermore, an analytical model for the penetration depth of the crater is developed accounting for the liquid inertia, viscosity, gravity, and surface tension. The model agrees well with the experiments at the early times of penetration far from the wall if the impact velocity is high. Finally, a scaling analysis of the residual film thickness on the wall is conducted demonstrating a good agreement with the numerical predictions.

A Hybrid Particle Level Set Method for Improved Interface Capturing

2002-11-01

Douglas Enright , Ronald Fedkiw , Joel H. Ferziger +1 more

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Phenomena of liquid drop impact on solid and liquid surfaces

1993-08-01

Martin Rein

The fluid dynamic phenomena of liquid drop impact are described and reviewed. These phenomena include bouncing, spreading and splashing on solid surfaces, and bouncing, coalescence and splashing on liquid surfaces. … The fluid dynamic phenomena of liquid drop impact are described and reviewed. These phenomena include bouncing, spreading and splashing on solid surfaces, and bouncing, coalescence and splashing on liquid surfaces. Further, cavitation and the entrainment of gas into an impacted liquid may be observed. In order to distinguish properly between the results of different experiments different impact scenarios are discussed. The specific conditions under which the above phenomena did occur in experiments are analyzed and the characteristics of drop impact phenomena are described in detail.

Maximal deformation of an impacting drop

2004-09-25

Christophe Clanet , Cédric Béguin , Denis Richard +1 more

We first study the impact of a liquid drop of low viscosity on a super-hydrophobic surface. Denoting the drop size and speed as are the liquid density and surface tension). … We first study the impact of a liquid drop of low viscosity on a super-hydrophobic surface. Denoting the drop size and speed as are the liquid density and surface tension). This law is also observed to hold on partially wettable surfaces, provided that liquids of low viscosity (such as water) are used. The law is interpreted as resulting from the effective acceleration experienced by the drop during its impact. Viscous drops are also analysed, allowing us to propose a criterion for predicting if the spreading is limited by capillarity, or by viscosity.

Numerical Calculation of the Fluid Dynamics of Drop-on-Demand Jets

1984-05-01

Jacob E. Fromm

A numerical method that makes use of the complete incompressible flow equations with a free surface is discussed and used to study an impulsively driven laminar jet. Flow behavior dependence … A numerical method that makes use of the complete incompressible flow equations with a free surface is discussed and used to study an impulsively driven laminar jet. Flow behavior dependence upon fluid properties (characterized by a Reynolds number over Weber number nondimensionalization) is compared for drop integrity purposes. Several variations of square wave pressure history applied at a nozzle inlet are discussed in relation to drop velocities produced and structure of ejected drops. Timewise development of flow both interior and exterior to the nozzle is illustrated through computed contour sequences.

Regimes of coalescence and separation in droplet collision

1997-01-25

J. Qian , Chung K. Law

An experimental investigation of the binary droplet collision dynamics was conducted, with emphasis on the transition between different collision outcomes. A series of time-resolved photographic images which map all the … An experimental investigation of the binary droplet collision dynamics was conducted, with emphasis on the transition between different collision outcomes. A series of time-resolved photographic images which map all the collision regimes in terms of the collision Weber number and the impact parameter were used to identify the controlling factors for different outcomes. The effects of liquid and gas properties were studied by conducting experiments with both water and hydrocarbon droplets in environments of different gases (air, nitrogen, helium and ethylene) and pressures, the latter ranging from 0.6 to 12 atm. It is shown that, by varying the density of the gas through its pressure and molecular weight, water and hydrocarbon droplets both exhibit five distinct regimes of collision outcomes, namely (I) coalescence after minor deformation, (II) bouncing, (III) coalescence after substantial deformation, (IV) coalescence followed by separation for near head-on collisions, and (V) coalescence followed by separation for off-centre collisions. The present result therefore extends and unifies previous experimental observations, obtained at one atmosphere air, that regimes II and II do not exist for water droplets. Furthermore, it was found that coalescence of the hydrocarbon droplets is promoted in the presence of gaseous hydrocarbons in the environment, suggesting that coalescence is facilitated when the environment contains vapour of the liquid mass. Collision at high-impact inertia was also studied, and the mechanisms for separation of the coalescence are discussed based on time-resolved collision images. A coalescence/separation criterion defining the transition between regimes III and IV for the head-on collisions was derived and found to agree well with the experimental data.

Modelling Merging and Fragmentation in Multiphase Flows with SURFER

1994-07-01

Bruno Lafaurie , Carlo Nardone , Ruben Scardovelli +2 more

A Front-Tracking Method for the Computations of Multiphase Flow

2001-05-01

Grétar Tryggvason , Bernard Bunner , Asghar Esmaeeli +6 more

Spread and rebound of liquid droplets upon impact on flat surfaces

1997-09-01

Ted Mao , D. Kuhn , Honghi Tran

Abstract The spread and rebound of droplets upon impact on flat surfaces at room temperature were studied over a wide range of impact velocities (0.5–6 m/s), viscosities (1–100 mPa.s), static … Abstract The spread and rebound of droplets upon impact on flat surfaces at room temperature were studied over a wide range of impact velocities (0.5–6 m/s), viscosities (1–100 mPa.s), static contact angles (30–120°), droplet sizes (1.5–3.5 mm), and surface roughnesses using a fast‐shutter‐speed CCD camera. The maximum spread of a droplet upon impact depended strongly on the liquid viscosity and the impact velocity. The tendency of a droplet to deposit or to rebound is determined primarily by the liquid viscosity and the liquid/substrate static contact angle. A model more broadly applicable than existing models was developed to predict maximum spread as a function of the Reynolds number, the Weber number, and the static contact angle. Based on the conservation of energy, a rebound model is proposed that predicts the tendency to rebound as a function of maximum spread and static contact angle. The maximum‐spread model prediction agrees to within 10% with more than 90% of the experimental data from different sources. In the current study, the rebound model successfully predicts the tendency of a droplet to rebound.

A conservative level set method for two phase flow

2005-06-22

Elin Olsson , Gunilla Kreiss

On the collision of a droplet with a solid surface

1991-01-08

S. Chandra , C. Thomas Avedisian

The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure … The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The primary parameter was the surface temperature, which ranged from 24°C to above the Leidenfrost temperature of the liquid. Experiments were also performed on a droplet impacting a surface on which there existed a liquid film created by deposition of a prior droplet. The evolution of wetted area and spreading rate, both of a droplet on a stainless steel surface and of a droplet spreading over a thin liquid film, were found to be independent of surface temperature during the early period of impact. This result was attributed to negligible surface tension and viscous effects, and in consequence the measurements made during the early period of the impact process were in good agreement with previously published analyses which neglected these effects. A single bubble was observed to form within the droplet during impact at low temperatures. As surface temperature was increased the population of bubbles within the droplet also increased because of progressive activation of nucleation sites on the stainless steel surface. At surface temperatures near to the boiling point of heptane, a spoke-like cellular structure in the liquid was created during the spreading process by coalescence of a ring of bubbles that had formed within the droplet. At higher temperatures, but below the Leidenfrost point, numerous bubbles appeared within the droplet, yet the overall droplet shape, particularly in the early stages of impact (< 0.8 ms), was unaffected by the presence of these bubbles. The maximum value of the diameter of liquid which spreads on the surface is shown to agree with predictions from a simplified model.

DROP IMPACT DYNAMICS: Splashing, Spreading, Receding, Bouncing…

2005-12-17

Alexander L. Yarin

The review deals with drop impacts on thin liquid layers and dry surfaces. The impacts resulting in crown formation are referred to as splashing. Crowns and their propagation are discussed … The review deals with drop impacts on thin liquid layers and dry surfaces. The impacts resulting in crown formation are referred to as splashing. Crowns and their propagation are discussed in detail, as well as some additional kindred, albeit nonsplashing, phenomena like drop spreading and deposition, receding (recoil), jetting, fingering, and rebound. The review begins with an explanation of various practical motivations feeding the interest in the fascinating phenomena of drop impact, and the above-mentioned topics are then considered in their experimental, theoretical, and computational aspects.

Nonlinear dynamics and breakup of free-surface flows

1997-07-01

Jens Eggers

Surface-tension-driven flows and, in particular, their tendency to decay spontaneously into drops have long fascinated naturalists, the earliest systematic experiments dating back to the beginning of the 19th century. Linear … Surface-tension-driven flows and, in particular, their tendency to decay spontaneously into drops have long fascinated naturalists, the earliest systematic experiments dating back to the beginning of the 19th century. Linear stability theory governs the onset of breakup and was developed by Rayleigh, Plateau, and Maxwell. However, only recently has attention turned to the nonlinear behavior in the vicinity of the singular point where a drop separates. The increased attention is due to a number of recent and increasingly refined experiments, as well as to a host of technological applications, ranging from printing to mixing and fiber spinning. The description of drop separation becomes possible because jet motion turns out to be effectively governed by one-dimensional equations, which still contain most of the richness of the original dynamics. In addition, an attraction for physicists lies in the fact that the separation singularity is governed by universal scaling laws, which constitute an asymptotic solution of the Navier-Stokes equation before and after breakup. The Navier-Stokes equation is thus continued uniquely through the singularity. At high viscosities, a series of noise-driven instabilities has been observed, which are a nested superposition of singularities of the same universal form. At low viscosities, there is rich scaling behavior in addition to aesthetically pleasing breakup patterns driven by capillary waves. The author reviews the theoretical development of this field alongside recent experimental work, and outlines unsolved problems.

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DIFFUSE-INTERFACE METHODS IN FLUID MECHANICS

1998-01-01

Daniel Anderson , G. B. McFadden , A. A. Wheeler

▪ Abstract We review the development of diffuse-interface models of hydrodynamics and their application to a wide variety of interfacial phenomena. These models have been applied successfully to situations in … ▪ Abstract We review the development of diffuse-interface models of hydrodynamics and their application to a wide variety of interfacial phenomena. These models have been applied successfully to situations in which the physical phenomena of interest have a length scale commensurate with the thickness of the interfacial region (e.g. near-critical interfacial phenomena or small-scale flows such as those occurring near contact lines) and fluid flows involving large interface deformations and/or topological changes (e.g. breakup and coalescence events associated with fluid jets, droplets, and large-deformation waves). We discuss the issues involved in formulating diffuse-interface models for single-component and binary fluids. Recent applications and computations using these models are discussed in each case. Further, we address issues including sharp-interface analyses that relate these models to the classical free-boundary problem, computational approaches to describe interfacial phenomena, and models of fully miscible fluids.

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Coalescence of liquid drops

1999-12-25

Jens Eggers , John R. Lister , Howard A. Stone

When two drops of radius R touch, surface tension drives an initially singular motion which joins them into a bigger drop with smaller surface area. This motion is always viscously … When two drops of radius R touch, surface tension drives an initially singular motion which joins them into a bigger drop with smaller surface area. This motion is always viscously dominated at early times. We focus on the early-time behaviour of the radius r m of the small bridge between the two drops. The flow is driven by a highly curved meniscus of length 2π r m and width Δ [Lt ] r m around the bridge, from which we conclude that the leading-order problem is asymptotically equivalent to its two-dimensional counterpart. For the case of inviscid surroundings, an exact two-dimensional solution (Hopper 1990) shows that Δ ∝ r 3 m and r m ∼( t γ/πη) ln [ t γ(η R )]; and thus the same is true in three dimensions. We also study the case of coalescence with an external viscous fluid analytically and, for the case of equal viscosities, in detail numerically. A significantly different structure is found in which the outer-fluid forms a toroidal bubble of radius Δ ∝ r 3/2 m at the meniscus and r m ∼( t γ/4πη) ln [ t γ/(η R )]. This basic difference is due to the presence of the outer-fluid viscosity, however small. With lengths scaled by R a full description of the asymptotic flow for r m ( t )[Lt ]1 involves matching of lengthscales of order r 2 m , r 3/2 m , r m , 1 and probably r 7/4 m .

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Impact of drops on solid surfaces: self-similar capillary waves, and splashing as a new type of kinematic discontinuity

1995-01-25

Alexander L. Yarin , Daniel A. Weiss

The impact of drops impinging one by one on a solid surface is studied experimentally and theoretically. The impact process is observed by means of a charge-coupled-device camera, its pictures … The impact of drops impinging one by one on a solid surface is studied experimentally and theoretically. The impact process is observed by means of a charge-coupled-device camera, its pictures processed by computer. Low-velocity impact results in spreading and in propagation of capillary waves, whereas at higher velocities splashing (i.e. the emergence of a cloud of small secondary droplets, absent in the former case) sets in. Capillary waves are studied in some detail in separate experiments. The dynamics of the extension of liquid lamellae produced by an impact in the case of splashing is recorded. The secondary-droplet size distributions and the total volume of these droplets are measured, and the splashing threshold is found as a function of the impact parameters. The pattern of the capillary waves is predicted to be self-similar. The calculated wave profile agrees well with the experimental data. It is shown theoretically that the splashing threshold corresponds to the onset of a velocity discontinuity propagating over the liquid layer on the wall. This discontinuity shows several aspects of a shock. In an incompressible liquid such a discontinuity can only exist in the presence of a sink at its front. The latter results in the emergence of a circular crown-like sheet virtually normal to the wall and propagating with the discontinuity. It is predicted theoretically and recorded in the experiment. The crown is unstable owing to the formation of cusps at the free rim at its top edge, which results in the splashing effect. The onset velocity of splashing and the rate of propagation of the kinematic discontinuity are calculated and the theoretical results agree fairly well with the experimental data. The structure of the discontinuity is shown to match the outer solution.

DIRECT NUMERICAL SIMULATION OF FREE-SURFACE AND INTERFACIAL FLOW

1999-01-01

Ruben Scardovelli , Stéphane Zaleski

The Deformation of Small Viscous Drops and Bubbles in Shear Flows

1984-01-01

J.M. Rallison

DROP AND SPRAY FORMATION FROM A LIQUID JET

1998-01-01

S. P. Lin , Rolf D. Reitz

▪ Abstract A liquid jet emanating from a nozzle into an ambient gas is inherently unstable. It may break up into drops of diameters comparable to the jet diameter or … ▪ Abstract A liquid jet emanating from a nozzle into an ambient gas is inherently unstable. It may break up into drops of diameters comparable to the jet diameter or into droplets of diameters several orders of magnitude smaller. The sizes of the drops formed from a liquid jet without external control are in general not uniform. The sizes as well as the size distribution depend on the range of flow parameters in which the jet is produced. The jet breakup exhibits different characteristics in different regimes of the relevant flow parameters because of the different physical mechanisms involved. Some recent works based on linear stability theories aimed at the delineation of the different regimes and elucidation of the associated physical mechanisms are reviewed, with the intention of presenting current scientific knowledge on the subject. The unresolved scientific issues are pointed out.

Drop Impact on a Solid Surface

2015-09-22

Christophe Josserand , S. T. Thoroddsen

A drop hitting a solid surface can deposit, bounce, or splash. Splashing arises from the breakup of a fine liquid sheet that is ejected radially along the substrate. Bouncing and … A drop hitting a solid surface can deposit, bounce, or splash. Splashing arises from the breakup of a fine liquid sheet that is ejected radially along the substrate. Bouncing and deposition depend crucially on the wetting properties of the substrate. In this review, we focus on recent experimental and theoretical studies, which aim at unraveling the underlying physics, characterized by the delicate interplay of not only liquid inertia, viscosity, and surface tension, but also the surrounding gas. The gas cushions the initial contact; it is entrapped in a central microbubble on the substrate; and it promotes the so-called corona splash, by lifting the lamella away from the solid. Particular attention is paid to the influence of surface roughness, natural or engineered to enhance repellency, relevant in many applications.

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On spray formation

2004-01-10

Philippe Marmottant , Emmanuel Villermaux

We depict and analyse the successive steps of atomization of a liquid jet when a fast gas stream blows parallel to its surface. Experiments performed with various liquids in a … We depict and analyse the successive steps of atomization of a liquid jet when a fast gas stream blows parallel to its surface. Experiments performed with various liquids in a fast air flow show that the liquid destabilization proceeds from a two-stage mechanism: a shear instability first forms waves on the liquid. The transient acceleration experienced by the liquid suggests that a Rayleigh–Taylor type of instability is triggered at the wave crests, producing liquid ligaments which further stretch in the air stream and break into droplets. The primary wavelength . This distribution bears an exponential tail characteristic of the broad size statistics in airblast sprays.

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OUTCOMES FROM A DROP IMPACT ON SOLID SURFACES

2001-01-01

Romain Rioboo , Cameron Tropea , Marco Marengo

A qualitative analysis of the various outcomes of a drop impact on solid surfaces with different roughness and wettability is carried out. Water, ethanol, different mixtures of glycerin and water, … A qualitative analysis of the various outcomes of a drop impact on solid surfaces with different roughness and wettability is carried out. Water, ethanol, different mixtures of glycerin and water, liquid alloys, and silicone oil were used to provide a wide range of material properties such as surface tension, viscosity, and density. The impact velocity was varied by moving the drop generator vertically with respect to tie plate. Also two drop diameter classes were considered. A variation of roughness amplitude and wavelength was achieved using a laser ablation process on polyvinyl chloride and glass substrates, creating a deterministic microstructure. A highly nonwettable rough surface was prepared with alkylketene dimer (AKD) [1]. A first classification of the different outcomes, in terms of splash, rebound, partial rebound, deposition, and other features, is presented.

A numerical method for solving incompressible viscous flow problems

1967-08-01

Alexandre J. Chorin

Study of grid convergence of a numerical model of dynamics of a polydispersonic coagulating gas suspension

2025-06-23

Д. А. Тукмаков | Modeling of systems and processes

In this paper, the grid convergence of a numerical model of the dynamics of a polydisperse coagulating gas suspension is investigated. The processes of coagulating gas suspension dynamics are found … In this paper, the grid convergence of a numerical model of the dynamics of a polydisperse coagulating gas suspension is investigated. The processes of coagulating gas suspension dynamics are found in liquid purification devices for dusty media. The process of particle coagulation was simulated when droplet fractions were injected into a stream of dusty medium. The carrier medium is described as a viscous compressible heat-conducting gas. The dispersed phase of the gas suspension was described taking into account the particle dispersion - the density and particle dispersion were set separately for each fraction. The presented mathematical model belongs to the type of continuous mathematical models of dynamics of inhomogeneous media, which involves the integration of a system of equations of motion of a continuous medium for each component of the mixture. The dynamics of dispersed inclusions is described taking into account the changing values of the volume content of each fraction. The process of particle coagulation was described by the mathematical model of collisional coagulation. One of the varieties of the finite difference method was used for the numerical solution. When implementing the finite difference method, a nonlinear correction scheme for a discrete function was used. As a result of calculations based on a sequence of grid partitions of a physical domain, the grid convergence of the numerical model was revealed. The influence of the grid parameters on the calculation results of the particle coagulation process in an inhomogeneous flow was also investigated.

Mixing performance test and uniformity analysis of a two-stage injection jet on-line mixer

2025-06-23

Ping Jiang , Siliang Xiang , Wenwu Hu +4 more | PLoS ONE

With the mixing of water and pesticides being a critical step, which is often performed using mixers. Traditional mixers, however, frequently exhibit issues such as uneven mixing and limited ratios. … With the mixing of water and pesticides being a critical step, which is often performed using mixers. Traditional mixers, however, frequently exhibit issues such as uneven mixing and limited ratios. A dual-stage injection jet online mixer was designed to enhance the uniformity of pesticide and water mixing. This paper presents performance tests and uniformity analysis of this mixer, aiming to assess its effectiveness post-installation and to determine if it meets the required mixing performance and uniformity standards. Image analysis was utilized for qualitative assessment, revealing that the mixer's two-dimensional curves in both axial and radial directions matched the pattern of pure pesticides. The root mean square error (RMSE) decreased with increasing mixing ratios, ranging from a minimum of 8.57% at a 300:1 ratio to a maximum of 9.94% at 2000:1. These variations were minimal, indicating good homogeneity across different ratios. Quantitative analysis using UV spectrophotometry showed that the actual mass concentration of the mixture deviated by less than 0.1% from the expected values at different sampling times, confirming superior temporal distribution uniformity. The variation in mixture mass concentration was insignificant across different locations, and the error variation at the same mixing ratio was less than 0.03%, indicating an excellent spatial distribution uniformity of the mixer. These findings demonstrate that the two-stage injection jet online mixer is effective over a wide range of mixing ratios, providing theoretical and technical support for accurate online variable spraying. This advancement is crucial for enhancing pesticide mixing efficiency and promoting sustainable agricultural development.

Lateral migration and bouncing of a deformable bubble rising near a vertical wall. Part 2. Highly inertial regimes

2025-06-18

Pengyu Shi , Jie Zhang , Jacques Magnaudet | Journal of Fluid Mechanics

The fate of deformable buoyancy-driven bubbles rising near a vertical wall under highly inertial conditions is investigated numerically. In the absence of path instability, simulations reveal that, when the Galilei … The fate of deformable buoyancy-driven bubbles rising near a vertical wall under highly inertial conditions is investigated numerically. In the absence of path instability, simulations reveal that, when the Galilei number, $Ga$ , which represents the buoyancy-to-viscous force ratio, exceeds a critical value, bubbles escape from the near-wall region after one to two bounces, while at smaller $Ga$ they perform periodic bounces without escaping. The escape mechanism is rooted in the vigorous rotational flow that forms around a bubble during its bounce at high enough $Ga$ , resulting in a Magnus-like repulsive force capable of driving it away from the wall. Path instability takes place with bubbles whose Bond number, the buoyancy-to-capillary force ratio, exceeds a critical $Ga$ -dependent value. Such bubbles may or may not escape from the wall region, depending on the competition between the classical repulsive wake–wall interaction mechanism and a specific wall-ward trapping mechanism. The latter results from the reduction of the bubble oblateness caused by the abrupt drop of the rise speed when the bubble–wall gap becomes very thin. Owing to this transient shape variation, bubbles exhibiting zigzagging motions with a large enough amplitude experience larger transverse drag and virtual mass forces when departing from the wall than when returning to it. With moderately oblate bubbles, i.e. in an intermediate Bond number range, this effect is large enough to counteract the repulsive interaction force, forcing such bubbles to perform a periodic zigzagging-like motion at a constant distance from the wall.

Experimental investigation on the behavior and heat transfer of droplet impacting on heated surface

2025-06-18

Weishi Peng , LUO Hanwen , Rongxuan Zhang +1 more | Experimental Thermal and Fluid Science

Numerical simulation of dynamic wetting in ternary fluids flows on curved substrates

2025-06-18

Chunyu Zhang , Jian-Yu Lin , Haoran Liu | Computers & Fluids

Full-process aerosol jet printing modelling: achieving high-fidelity simulation via coupling jetting and deposition

2025-06-18

Yufeng Jin , Hao Yi , Huajun Cao +1 more | Virtual and Physical Prototyping

Particle–bubble dynamics blocking sediment diffusion in the core region of bubble plumes

2025-06-18

Yuzhu Wang , Jing Zou , Bo Shui +2 more | Particulate Science And Technology

An efficient naturally sharpened stabilized multiphase flow formulation for modeling underwater explosions

2025-06-18

Hoang T. Nguyen , Shaunak Shende , Yuri Bazilevs | Computational Mechanics

Euler—Euler simulation of multi-regime two-phase flows with thin liquid films

2025-06-17

Paul Porombka , Jan Schlottke | Experimental and Computational Multiphase Flow

Influence of Fuel Surface Tension and Viscosity on Internal Flow Bubble Formation and Atomization in Flash Boiling Sprays

2025-06-16

Yijia Zhang , Yilong Li , Shangning Wang +4 more | SAE technical papers on CD-ROM/SAE technical paper series

<div class="section abstract"><div class="htmlview paragraph">Flash boiling atomization is considered a promising atomization technique for combustion applications in automotive powertrains. It can potentially address the deteriorated atomization issue for alternative fuels … <div class="section abstract"><div class="htmlview paragraph">Flash boiling atomization is considered a promising atomization technique for combustion applications in automotive powertrains. It can potentially address the deteriorated atomization issue for alternative fuels (such as methanol) in internal combustion engines. However, it has been observed that flash boiling spray atomization for methanol fuels is not as effective as that for traditional alkane-based fuels. This work aims to explain such phenomena using transparent nozzles to reveal the impact of internal vaporization on external spray breakups. Three different working fluids, including methanol, ethanol, and pentane, are tested with elevated temperatures. The flow patterns and external liquid breakup are shown with the high-speed imaging technique. It is found that the internal phase change of the base working fluid is suppressed when ethanol or methanol is used instead of pentane. Consequently, the external liquid breakup is also hindered due to insufficient vapor phase inside the nozzle. It is held that increased surface tension and viscosity have made the nucleation process more challenging compared with typical gasoline fuels.</div></div>

Droplet Impact-Based Microliter Viscometry

2025-06-16

Shuxian Tang , Xiang Li , Wanying Wang +7 more | Analytical Chemistry

Characterizing liquid viscosity and rheological properties with small sample volumes is crucial in fields where liquid samples are often limited, such as biological fluids for biomedical diagnostics and trace chemical … Characterizing liquid viscosity and rheological properties with small sample volumes is crucial in fields where liquid samples are often limited, such as biological fluids for biomedical diagnostics and trace chemical products. However, traditional viscometers often require large sample volumes, and many existing small-volume viscometry techniques fall short in analyzing non-Newtonian fluids due to their limited shear rate range. While microfluidics-based viscometers offer flexibility in shear rate control, they are generally associated with intricate fabrication processes and high costs. Here, we introduce a droplet impact-based microliter viscometry (DI-μV), building on a quantitative relationship between viscosity and the maximum spreading factor of droplets impacting super-repellent surfaces. Leveraging the sufficient viscous effect during droplet impact, DI-μV can measure effective viscosity across varying effective shear rates and probe the rheological properties of liquids, using only μL-scale volumes. As a tool for viscosity measurement, DI-μV exhibits minimal sample consumption, adjustable effective shear rate, self-cleaning capabilities, operational simplicity, and cost-effectiveness, thereby offering relevant practical implications.

Monitoring the Soft Sludge and Water Content of Hydraulic Oil Samples Using Drop Analysis

2025-06-16

Alena Breznická , Pavol Mikuš , Ľudmila Timárová +1 more | Key engineering materials

Water or moisture contained in any form in hydraulic oil is not desirable in a hydraulic system. It can cause emulsification of the oil, which results in deterioration or rupture … Water or moisture contained in any form in hydraulic oil is not desirable in a hydraulic system. It can cause emulsification of the oil, which results in deterioration or rupture of the lubricating film, as well as corrosion of metal parts in this system. This corrosion can cause damage to metal parts and impair their functionality. Regular control of the amount of water in hydraulic oil is therefore a very important part of hydraulic oil diagnostics. The article presents a case study of monitoring the condition of hydraulic oil for water content values, which were determined according to the Karl Fischer method. The analysis of hydraulic oil in the article was also an experimental drop analysis for monitoring water in hydraulic oil, which we classify as a quick and simple chemical method aimed at indicatively demonstrating the presence of water in oil and the degree of oil contamination. This analysis belongs to non-dismantling technical diagnostics. Its greatest advantage is that with its help, oil analysis is faster and cheaper compared to analyses performed in laboratories.

Discrete motion modes of eccentric droplet impact on sessile droplet at low Ohnesorge and Weber numbers

2025-06-15

MIIN-JENG YAN , Zhenyu Ouyang , Chen Liu +3 more | Experiments in Fluids

Measurement of Lamella Thickness Evolution during Droplet Spreading on a Dry Surface and Insights into Energy Distribution during the Process

2025-06-15

Surendran Mikhil , Koushik Biswas , Shamit Bakshi | Langmuir

The present study deals with the evolution of a liquid film formed by droplet impact onto a dry flat surface at high Weber and Reynolds numbers. A Chromatic Confocal Sensor … The present study deals with the evolution of a liquid film formed by droplet impact onto a dry flat surface at high Weber and Reynolds numbers. A Chromatic Confocal Sensor is employed to measure the temporal evolution of the lamella thickness of the impacting droplet, and droplet spread factors are measured using shadow imaging. These measurements were then used to identify appropriate theoretical representations for different phases of the evolving droplet height/lamella thickness. The evolution of the lamella thickness is a critical input for estimating the energy dissipation in the boundary layer during lamella spread. Existing energy budgeting approaches consider a constant boundary layer thickness to estimate the boundary layer dissipation and predict the maximum spread of the droplet. The present study instead proposes the use of a transient boundary layer thickness along with a suitable velocity scale. Furthermore, the significance of considering early-stage energy dissipation in energy budgeting is demonstrated, and an approach for integrating both early-stage and wall boundary layer dissipations into an energy-based model is presented. A differential form of the energy balance equation is proposed for high Weber and Reynolds number impacts and is used to capture the time variation of the spreading diameter. The temporal evolution of the droplet spread factors obtained using this model is in good agreement with our measurements.

Numerical study of the atomization performance of coaxial and porous injectors in rocket engine applications

2025-06-14

Pradeep Raj , P.R. Parthasarathy , Ganesh Paramasivan | International Journal of Engine Research

The numerical study involved in comparing the atomization performance of coaxial and porous injectors using the coupled volume of fluid and discrete phase CFD model (coupled VOF-DPM). The study focuses … The numerical study involved in comparing the atomization performance of coaxial and porous injectors using the coupled volume of fluid and discrete phase CFD model (coupled VOF-DPM). The study focuses on the primary atomization region of the injection. The investigation is done to study the effect of water-air mass flow ratios on droplet parameters such as droplet size (SMD), axial and radial velocity, and the number of droplets at different injection times. Pore-level simulations are performed to study the performance of the porous injectors. It is observed that increasing the water-air mass flow ratio in both types of injectors leads to an increase in droplet size. The results showed that the droplet size produced by the coaxial injector is larger than that of the porous injector. Moreover, the number of droplets produced by the coaxial injector is lower than that produced by the porous injector. The smaller droplet size and larger number of droplets indicate better atomization in the porous injector.

Light-Induced Polymer Drop Splashing

2025-06-13

Marufa Akter Upoma , Huy Tran , C. Rose +3 more | Langmuir

This study seeks to understand the role of photodegradation of aqueous polymers in drop splashing. Polymer drop impact commonly occurs in various industrial applications, such as inkjet printing, spray coating, … This study seeks to understand the role of photodegradation of aqueous polymers in drop splashing. Polymer drop impact commonly occurs in various industrial applications, such as inkjet printing, spray coating, and agrochemical sprays. In agrochemicals, the various constituent components (e.g., adjuvants) impart multiple changes to the fluid dynamics and the wetting behaviors of the drops, as well as interact with the environmental conditions. The environmental conditions (e.g., thermal degradation, photodegradation, and oxidation) of the chemicals affect the shelf stability of the intended physicochemical properties of the chemicals, which are added to stabilize drift from the spray nozzles and minimize drop bouncing from leaves. The aging effects of the adjuvants in tandem with the already low pesticide delivery efficiency have an unknown effect on the agrochemical delivery efficiency and the related environmental burden from the increased runoff. Herein, we systematically photodegraded poly(ethylene oxide) (PEO) to probe the drop splashing behavior as a result of the simulated aging conditions. Dye was added to accelerate the degradation of the polymers and caused drops to splash at Weber numbers, where the pure PEO case did not, confirming the need to consider environmental factors which contribute to adjuvant aging in agrochemical applications. We have also conducted experiments with various concentrations of PEO to probe the changes in the splash dynamics as well as include surfactants, which played a marginal role in altering the splash dynamics under our parameter space. The significance of the study is that the degradation of the polymers influences the splashing and increases the amount of splashed droplets, indicating the importance of controlling the environmental conditions under which polymer solutions are stored.

3D numerical investigation of fragmentation of wood’s metal in water and estimation of particle size distribution

2025-06-12

M. Chandra Kumar , A. Jasmin Sudha | Nuclear Engineering and Design

Understanding the Role of Superhydrophobicity on Heat Transfer Enhancement During Dropwise Condensation in Humid Air Flow

2025-06-11

Antonio Abbatecola , Marco Tancon , Elena Colusso +4 more | Advanced Materials Interfaces

Abstract Superhydrophobic surfaces have been extensively studied to enhance heat transfer during moisture condensation. However, the existing literature presents conflicting results, with some studies reporting enhanced performance while others observe … Abstract Superhydrophobic surfaces have been extensively studied to enhance heat transfer during moisture condensation. However, the existing literature presents conflicting results, with some studies reporting enhanced performance while others observe a decline compared to hydrophilic surfaces. Furthermore, the effect of air velocity has been marginally addressed. In this work, superhydrophobic aluminum surfaces (advancing contact angle of 160°, contact angle hysteresis <1°) are fabricated by chemical etching followed by fluorosilane coating. Condensation tests are performed at constant air temperature (28 °C), while varying relative humidity (70%, 90%), dew‐to‐wall temperature difference (7–13 K) and air velocity (0.4–6 m s −1 ). It is found that, compared to the hydrophilic untreated surface, superhydrophobic surfaces do not offer any advantage at low air velocities (0.4 and 1 m s −1 ), while a condensation heat transfer coefficient increased by 30%–40% is achieved at high air velocities (4 and 6 m s −1 ). The performance is attributed to a more efficient droplet removal mechanism and enhanced vapor mass transfer through the non‐condensable gas layer, which is also associated with droplet‐induced vorticity, as confirmed by video analysis. The results clarify the operating conditions under which superhydrophobic surfaces are advantageous for applications of condensation from humid air, including dehumidification.

Universality of satellites in the breakup of a stretched fluid bridge

2025-06-09

Anna Frishman , Daniel Lecoanet | Physical Review Fluids

A modelling framework for jet penetration into soft gels – ERRATUM

2025-06-09

| Journal of Fluid Mechanics

A Comparison of Characteristics of Two-Liquid Droplets Fragmentation with a Variable Volatile Component

2025-06-05

Д.В. Антонов , Dmitrii I. Volokitin , O. V. Vysokomornaya +1 more | Industrial & Engineering Chemistry Research

Instability of a viscoelastic cylindrical liquid jet under the coupling effect of parametric resonance and Kelvin-Helmholtz instability

2025-06-01

Bo-qi Jia , Ziheng Yu , Jiawei Wang +4 more | Aerospace Science and Technology

Numerical investigation of force variations in successive high-speed liquid droplet impacts and data-driven modeling

2025-06-01

K. Fujisawa | Physics of Fluids

High-speed liquid droplet impacts were numerically investigated using compressible multicomponent Euler simulations to characterize the time-varying force exerted on each droplet. Successive impacts were examined at three impact Mach numbers … High-speed liquid droplet impacts were numerically investigated using compressible multicomponent Euler simulations to characterize the time-varying force exerted on each droplet. Successive impacts were examined at three impact Mach numbers in the range of 0.051 &lt; Ma &lt; 0.077. The trailing droplet was consistently experiencing a lower force than the leading droplet. Furthermore, a data-driven framework employing a physics-informed neural network was developed to analyze the influence of droplet spacing on successive high-speed droplet impacts.

Droplet dynamics in capillary parallel plate channel

2025-06-01

Damien Thomas , Stéphanie Lacour , Stéphane Zaleski | Computers & Fluids

Development of a Weakly Compressible Solver for Incompressible Two-Phase Flows

2025-06-01

Ashley Melvin , J.C. Mandal | Journal of Computational Physics

Energy conversion analysis for behavior transition in binary droplet collision at high Weber number

2025-06-01

Yuchen Wu , Yaning Wang , Y. Cai +2 more | Physics of Fluids

Studying energy conversion provides critical insights into the abnormal behavior transition from separation to coalescence following fingering (CFF) in binary droplet collisions at high Weber numbers (We). This study investigates … Studying energy conversion provides critical insights into the abnormal behavior transition from separation to coalescence following fingering (CFF) in binary droplet collisions at high Weber numbers (We). This study investigates the energy conversion dynamics of binary droplet collisions with an Ohnesorge number (Oh) of approximately 0.001 and We=30–650 through three-dimensional phase-field lattice Boltzmann simulation. Key findings reveal that the classical spreading theory [Jiang et al., “An experimental investigation on the collision behaviour of hydrocarbon droplets,” J. Fluid Mech. 234, 171–190 (1992)] leads to a significant overestimation of viscous dissipation by approximately 25% at high We, primarily due to the neglect of kinetic energy of internal flow at the spreading end point. A crucial finding reveals that the ratio of viscous dissipation rate to surface energy release rate during most of the merging stage is maintained at one-third, contrasting with the established value of one-half observed in soap film rupture studies. Based on this finding, a quantitative analysis for CFF further found that the additional dissipation caused by fingering needs to reach about onefold of the initial surface energy to cause the reflexive separation behavior to transform into coalescence behavior. Furthermore, this study attributes the low onset We of CFF in the gallium–indium–tin (GaInSn) droplets–gas system to its properties of significantly high density ratio and oscillation-induced surface tension reduction, challenging prior explanations based solely on low Oh.