Breakup Process Research Articles

The Origin of Non-thermal Fluctuations in Multiphase Flow in Porous Media

Core flooding experiments to determine multiphase flow in properties of rock such as relative permeability can show significant fluctuations in terms of pressure, saturation, and electrical conductivity. That is typically not considered in the Darcy scale interpretation but treated as noise. However, in recent years, flow regimes that exhibit spatio-temporal variations in pore scale occupancy related to fluid phase pressure changes have been identified. They are associated with topological changes in the fluid configurations caused by pore-scale instabilities such as snap-off. The common understanding of Darcy-scale flow regimes is that pore-scale phenomena and their signature should have averaged out at the scale of representative elementary volumes (REV) and above. In this work, it is demonstrated that pressure fluctuations observed in centimeter-scale experiments commonly considered Darcy-scale at fractional flow conditions, where wetting and non-wetting phases are co-injected into porous rock at small (<10−6) capillary numbers are ultimately caused by pore-scale processes, but there is also a Darcy-scale fractional flow theory aspect. We compare fluctuations in fractional flow experiments conducted on samples of few centimeters size with respective experiments andin-situmicro-CT imaging at pore-scale resolution using synchrotron-based X-ray computed micro-tomography. On that basis we can establish a systematic causality from pore to Darcy scale. At the pore scale, dynamic imaging allows to directly observe the associated breakup and coalescence processes of non-wetting phase clusters, which follow “trajectories” in a “phase diagram” defined by fractional flow and capillary number and can be used to categorize flow regimes. Connected pathway flow would be represented by a fixed point, whereas processes such as ganglion dynamics follow trajectories but are still overall capillary-dominated. That suggests that the origin of the pressure fluctuations observed in centimeter-sized fractional flow experiments are capillary effects. The energy scale of the pressure fluctuations corresponds to 105-106times the thermal energy scale. This means the fluctuations are non-thermal. At the centimeter scale, there are non-monotonic and even oscillatory solutions permissible by the fractional flow theory, which allow the fluctuations to be visible and—depending on exact conditions—significant at centimeter scale, within the viscous limit of classical (Darcy scale) fractional flow theory. That also means that the phenomenon involves both capillary aspects from the pore or cluster scale and viscous aspects of fractional flow and occurs right at the transition, where the physical description concept changes from pore to Darcy scale.

Vertical Characteristics of Raindrops Size Distribution over Sumatra Region from Global Precipitation Measurement Observation

The climatology of the vertical profile of raindrops size distribution (DSD) over Sumatra Region (10° S – 10° N, 90° E – 110° E) has been investigated using Global Precipitation Measurement (GPM) level 2 data from January 2015 to June 2018. DSD's vertical profile was observed through a vertical profile of corrected radar reflectivity (Ze) and two parameters of normalized gamma DSD, i.e., mass-weight mean diameter (Dm) and total drops concentration (Nw). Land-ocean contrast and rain type dependence of DSD over Sumatra were clearly observed. The values of Dm and Nw were larger in the land than in the ocean. Negative and positive gradients of Dm toward the surface were dominant during stratiform and convective rains, respectively, consistent with the Z gradient. Moreover, the negative gradient of stratiform rain in the ocean is larger than in land. Thus, the depletion of large drops is dominant over the ocean, which is due to the break-up process that can be observed from the increase of Nw. Raindrop growth of convective rains is more robust over the ocean than land that can be seen from a larger value of Dmgradient. The BB strength is slightly larger over land and coastal region than over the ocean, indicating that the riming process is more dominant over land and coastal regions than the ocean. Doi: 10.28991/esj-2021-01274 Full Text: PDF

Meso-Neoproterozoic proto-basins and oil–gas resources in China: Preface

The recent discovery of Meso-Neoproterozoic primary oil and gas reservoirs within ancient cratonic basins of the world has promoted studies on the mechanism and exploration of these primary reservoirs. The formation and distribution of oil and gas resources are controlled by the tectonic setting, paleogeography, paleo-environment and biological evolutionary history related to supercontinents. The nature and distribution of proto-type basins are a key to oil and gas exploration and evaluation for the Meso-Neoproterozoic basins. This special issue is focused on the theme of “Supercontinental breakup process, basin formation, late deformation, and oil and gas accumulation”. It aims to provide a cross section of the interdisciplinary methods adopted to study Meso-Neoproterozoic basin-forming tectonic settings and evolutionary processes in the three cratons of China, to unravel the tectonic reworking and formation of proto-basins, to reconstruct the tectonic paleogeography and prototype basin, and to identify the effect of the late superimposed geological events for the proto-type basins and their oil and gas petroleum systems.

Breakup regime and heat transfer of a vapor bubble within T-shaped branching microchannel

Understanding the transport characteristics and underlying mechanisms in microscale geometries is essential for microfluidic applications. While most fundamental studies in literatures focused on straight microchannels, the phase change process is still not fully understood for branching microchannels. In this study, a physically based high-fidelity numerical model is developed to investigate the breakup regime and phase change heat transfer of an isolated bubble within a T-shaped branching microchannel. The numerical model is first validated against both experimental data and numerical simulation in literatures, and a mesh independence study is performed to ensure the precision of the following simulations. Then, the influences of wall heat flux (50 W/m2 < q < 800 W/m2) and initial bubble size (0.64 < D* < 0.96) are investigated. Four distinct bubble breakup regimes can be recognized, namely non-breakup (NB) regime, “tunnel” breakup type one (TBⅠ) regime, “tunnel” breakup type two (TBⅡ) regime, and obstructed breakup (OB) regime. A phase diagram is plotted to describe the distribution of these regimes with respect to q and D*. The other important dynamic characteristics, such as two-phase flow structures, bubble deformation and growth are also investigated to help understanding the breakup process. In order to reveal the unique phase change heat transfer features within branching microchannel, the local heat transfer distribution and evolution are first quantitatively investigated on each channel wall, and then the influences of q and D* on the overall heat transfer performance are identified and compared with the single-phase heat transfer. The liquid film around the bubble and breakup dynamics are recognized as the key factors determining the phase change heat transfer performance within the microchannel and channel junction, respectively.

A Comparison of Soybean Oil Methyl Ester and Diesel Sprays Behavior and Atomization Characteristics

The present numerical study compares between spray characteristics of diesel and soybean oil methyl ester (SME biodiesel) under non-evaporating sprays. The spray structure of diesel and biodiesel fuel (soybean oil) in a common rail injection system are investigated and compared with that of available experimental data used image processing and atomization performance analysis. The proposed approach for the liquid phase, which based on the sprays’ statistical properties, is used to present the gas and liquid phases in an Eulerian-Eulerian approach. The main concept for this model is the possibility of describing a poly disperses spray by using moments of a drop number size distribution function. The main reason for less spray tip penetration in the (SME) comparing with diesel because a larger droplet diameters is the higher density, surface tension and viscosity of (SME). The fuel properties effect on the near nozzle structure is studied. The comparisons are referring that the spray drag, breakup and collision processes are promoted.

A Comparison of Soybean Oil Methyl Ester and Diesel Sprays behavior and atomization characteristics

The present numerical study compares between spray characteristics of diesel and soybean oil methyl ester (SME biodiesel) under non-evaporating sprays. The spray structure of diesel and biodiesel fuel (soybean oil) in a common rail injection system are investigated and compared with that of available experimental data used image processing and atomization performance analysis. The proposed approach for the liquid phase based on the statistical properties of sprays be used to describe the liquid and gas phases in an Eulerian-Eulerian approach. The main concept for this model is the possibility of describing a poly disperse spray by using moments of a drop number size distribution function. The main reason for less spray tip penetration in&#x0D; the (SME) comparing with diesel because a larger droplet diameters is the higher density, viscosity and surface tension of (SME). The effect of fuel properties on the near nozzle structure is studied. The comparisons are referring that the spray drag, breakup and collision processes are promoted.

Systematic study on the role of various higher-order processes in the breakup of weakly-bound projectiles

Abstract The virtual photon theory (VPT), which is based on first-order Coulomb dissociation restricted to the electric dipole (E1), has been successfully used to explain the breakup data for several cases. Our aim is to study the role of various higher-order processes that are ignored in the VPT, such as the nuclear breakup, interference between nuclear and Coulomb amplitudes, and multistep breakup processes mainly due to strong continuum-continuum couplings in the breakup of two-body projectiles on a heavy target at both intermediate and higher incident energies. For the purpose of numerical calculations, we employed eikonal version of three-body continuum-discretized coupled-channels (CDCC) reaction model. Our results for the breakup of 11Be and 17F on 208Pb target at 100, 250, and 520 MeV/A, show the importance of nuclear breakup contribution, and its significant role in the multistep processes. The multistep effect on Coulomb breakup for core-neutron projectile was found to be negligible, whereas it was important for core-proton projectile. Coulomb-nuclear interference (CNI) effect was also found to be non-negligible. Qantitatively, the multistep effects due to the nuclear breakup was found to depend on the incident energy through the energy dependence of the core-target and nucleon-target nuclear potentials. The nuclear breakup component, the CNI effect, and the multistep breakup processes are all found to be non-negligible; hence, the assumptions adopted in the VPT for the accurate description of breakup cross sections are not valid.

Explosive fragmentation of Prince Rupert\u2019s drops leads to well-defined fragment sizes

Anyone who has ever broken a dish or a glass knows that the resulting fragments range from roughly the size of the object all the way down to indiscernibly small pieces: typical fragment size distributions of broken brittle materials follow a power law, and therefore lack a characteristic length scale. The origin of this power-law behavior is still unclear, especially why it is such an universal feature. Here we study the explosive fragmentation of glass Prince Rupert’s drops, and uncover a fundamentally different breakup mechanism. The Prince Rupert’s drops explode due to their large internal stresses resulting in an exponential fragment size distribution with a well-defined fragment size. We demonstrate that generically two distinct breakup processes exist, random and hierarchical, that allows us to fully explain why fragment size distributions are power-law in most cases but exponential in others. We show experimentally that one can even break the same material in different ways to obtain either random or hierarchical breakup, giving exponential and power-law distributed fragment sizes respectively. That a random breakup process leads to well-defined fragment sizes is surprising and is potentially useful to control fragmentation of brittle solids.

Numerical simulation of the atomization of liquid transverse jet in supersonic airflow

The present study provides a numerical method for liquid jet atomization in supersonic gas crossflow. Compressibility of the gas and incompressibility of the liquid are considered. High-order accurate weighted essentially non-oscillatory schemes and the Harten–Lax–van Leer contact approximate Riemann solver are used for gas flows. Liquid flow is simulated by the Chorin projection method. The motion of the sharp interface between the gas and liquid is simulated by the volume of fluid method. In order to verify the accuracy of the numerical method, numerical and experimental results for the droplet breakup in the supersonic gas flow are compared. The method is employed to simulate the liquid jet atomization in the supersonic gas crossflow. According to numerical results, the breakup process is analyzed for four different stages. The discussion for the effect of the Mach number for the gas crossflow on the liquid jet atomization is given.

Aggregation and breakup of colloidal particle aggregates in shear flow: A combined Monte Carlo - Stokesian dynamics approach

A method for the simulation of aggregation and breakup processes in colloidal particle suspensions is presented. The method combines a Monte Carlo algorithm to determine, on the basis of probabilistic considerations, the sequence of aggregation and breakup events, and a Discrete Element Method, built in the framework of Stokesian dynamics and contact mechanics, to accurately reproduce them. Liquid-solid suspensions subject to a uniform shear stress are investigated. The model is seen to be able to reproduce the typical dynamic steady state which is observed in colloidal suspensions under severe shearing, in which the effects of aggregation and breakup balance each other. The structural properties of the aggregates and the dynamics of the aggregation and breakup phenomena are characterized in detail. Both fragmentation and erosion are seen to contribute to the breakup process, which is characterized by an exponent similar to the one reported in the literature for compact clusters.

Dynamics of non-Newtonian droplet breakup with partial obstruction in microfluidic Y-junction

Dynamics of non-Newtonian droplet (CMC aqueous solution) breakup with partial obstruction in microfluidic Y-junction was visually investigated. Three breakup stages were found: squeezing, transition and pinch-off. The effects of the concentration c of CMC, continuous capillary number Cac and dispersed phase local capillary number Cad on droplet breakup were studied. In squeezing stage and transition stage, the breakup process could be promoted by increasing Cad or decreasing c. The pinch-off stage relied primarily on the surface tension and was almost independent of inertial force and viscous force. For the shear thinning non-Newtonian droplet, the length of the daughter droplet was always linearly stretched with time until breakup and the maximum gap width increased with Cac, but decreased with the increases of c and Cad.

Rifted margins classification and forcing parameters

Rifted margins are the result of the successful process of thinning and breakup of the continental lithosphere leading to the formation of new oceanic lithosphere. Observations on rifted margins are now integrating an increasing amount of multi-channel seismic data and drilling of several Continent-Ocean Transitions. Based on large scale geometries and domains observed on high-quality multi-channel seismic data, this article proposes a classification reflecting the mechanical behavior of the crust from localized to diffuse deformation (strong/coupled to weak/decoupled mechanical behaviors) and magmatic intensity leading to breakup from magma-rich to magma-poor margins. We illustrate a simple classification based on mechanical behavior and magmatic production with examples of rifted margins. We propose a non-exhaustive list of forcing parameters that can control the initial rifting conditions but also their evolution through time. Therefore, rifted margins are not divided into opposing types, but described as a combination and continuum that can evolve through time and space.

Effects of Radial–Tangential Discharge Channels on a Rotary Atomizer Performance

The effects of tangential injection on the primary breakup dynamic and spray characteristics of a rotary atomizer are experimentally investigated under atmospheric conditions. To achieve this goal, two types of atomizers with radial and radial–tangential discharge channels are used to compare their results. The breakup process as well as the primary breakup length are compared with the aid of the high-magnification shadow imaging technique. The droplet size distributions are obtained by the use of the particle/droplet image analyses technique at the same plane of measurement to compare the atomization quality in radial and radial–tangential discharge channels. The results reveal that the breakup process of the injected liquid stream is extensively affected by the tangential orientation of discharge channels of the atomizer disk. The atomization process is improved in the radial–tangential case as a result of the enhancement of aerodynamic forces acting on the exposed surface of the liquid stream. The droplet sizing indicates that the Sauter mean diameter values are decreased by the application of radial–tangential injection in all considered operating conditions.

Exploring the structure of 29Ne

We apply a fully quantum mechanical Coulomb breakup theory under the aegis of post form finite-range distorted wave Born approximation to analyze the elastic Coulomb breakup of 29Ne on 208Pb at 244MeV/u. We calculate several reaction observables to quantify its structural parameters. One-neutron removal cross section is calculated to check the consistency of the ground state configuration of 29Ne with the available experimental data. A scrutiny of the parallel momentum distribution of the charged fragment reveals a full width at half maximum of 82MeV/c, which is in good agreement with the experimental value and indicates a moderate halo for a nearly spherical 29Ne in the 28Ne(0+)⊗2p3/2ν ground state. The energy-angular distributions and average momentum of the charged fragment point to the absence of post-acceleration effects in the breakup process, a desirable result for elastic breakup.

Statistical characteristics of raindrop size distribution over the Western Ghats of India: wet versus dry spells of the Indian summer monsoon

Abstract. The nature of raindrop size distribution (DSD) is analyzed for wet and dry spells of the Indian summer monsoon (ISM) in the Western Ghats (WG) region using Joss–Waldvogel disdrometer (JWD) measurements during the ISM period (June–September) in 2012–2015. The observed DSDs are fitted with a gamma distribution. Observations show a higher number of smaller drops in dry spells and more midsize and large drops in wet spells. The DSD spectra show distinct diurnal variation during wet and dry spells. The dry spells exhibit a strong diurnal cycle with two peaks, while the diurnal cycle is not very prominent in the wet spells. Results reveal the microphysical characteristics of warm rain during both wet and dry periods. However, the underlying dynamical parameters, such as moisture availability and vertical wind, cause the differences in DSD characteristics. The higher moisture and strong vertical winds can provide sufficient time for the raindrops to grow bigger in wet spells, whereas higher temperature may lead to evaporation and drop breakup processes in dry spells. In addition, the differences in DSD spectra with different rain rates are also observed. The DSD spectra are further analyzed by separating them into stratiform and convective rain types. Finally, an empirical relationship between the slope parameter λ and the shape parameter μ is derived by fitting the quadratic polynomial during wet and dry spells as well as for stratiform and convective types of rain. The μ–λ relations obtained in this work are slightly different compared to previous studies. These differences could be related to different rain microphysics such as collision–coalescence and breakup.

Modeling study on drop breakup time in turbulent dispersions

Drop breakup time describes the time scale of the drop breakup process. In this work, a mathematical model for drop breakup time is constructed by the dimensional analysis method. The adjustable parameters in the model are determined and further validated by comparing with the experimental data in the literature. Results show that the model accurately predicts the drop breakup time when Weber number (WeL) is low. Further, we analyzed the effect of drop diameter, WeL, interfacial tension, and drop viscosity on the breakup time. It is noted that the breakup time increases with the increase of drop diameter and viscosity, while decreases with the increase of WeL and interfacial tension. The internal flow mechanism was proposed to illustrate the influence of the interfacial tension on the breakup time. The breakup time model can be further used in the construction of breakup kernels in a population balance model.

Study on the Spray Characteristics and Oscillation Mechanism of a Feedback-Free Internal Impinging Nozzle

Feedback-free internal impinging nozzle, which can generate fan-shape oscillating spray with constant pendulum angle, is well-suitable for flow control, as it has a wide range of operation frequency and does not require additional energy for moving parts. In this study, the spray characteristics of an internal impinging nozzle were investigated in an open atomization test bench by utilizing high-speed Schlieren technology and Malvern particle size analyzer. To better understand the jet oscillation mechanism and to evaluate its impact on the spray sweeping behaviors, a 3D CFD simulation was carried out, which takes the nozzle internal flow dynamics and the external spray morphology into account. The results indicate that the sweeping behavior of the emitted jet is caused by the impingement between two opposite internal jets inside the nozzle. A bi-model spray spatial flow distribution of the nozzle is observed with varying oscillating frequencies and constant spray pendulum angle at different injection pressures. The oscillation process can be divided into two stages depending on jet breakup processes, and the spray waveforms are influenced by the ratio of the durations of these two stages.

Experimental study on the spray steadiness of an internal-mixing twin-fluid atomizer

Liquid breakup intensity in the near-nozzle region and droplet size fluctuations at different downstream positions of an internal-mixing twin-fluid (IMTF) atomizer were studied by using a high-speed camera and a Malvern Spraytec diffractometer, and the effect of operating conditions on spray steadiness was analyzed. The results show that under the operating conditions of this study, the primary breakup process of IMTF atomization is affected by various breakup modes, and the characteristic droplet diameters at a given position exhibit different degrees of fluctuation, which can be considered to be inherently unsteady. The primary breakup process at medium gas/liquid mass flow ratio (GLR) is more unsteady than that at either small GLR or large GLR. At different downstream positions, the steadiness of larger droplets is significantly lower than that of smaller droplets. Compared with the near-nozzle region, the spray steadiness is significantly improved in the fully developed region. Moreover, frequency spectrum analysis performed on the time-resolved data of various droplet characteristic diameters in the near-nozzle region shows the presence of a pulsation frequency in the spectrum diagrams. This pulsation frequency can be used for evaluating the influence of GLR on the spray steadiness.

Proton-halo breakup dynamics for the breakup threshold in the ε 0 → 0 limit

Proton-halo breakup behavior in the limit (where is the ground-state binding energy) is studied around the Coulomb barrier in the reaction for the first time. For practical purposes, apart from the experimental binding energy of 137 keV, three more arbitrarily chosen values (1, 0.1, 0.01 keV) are considered. It is first shown that the Coulomb barrier between the core and the proton prevents the system from reaching the state of an open proton-halo system, which, among other factors, would require the ground-state wave function to extend to infinity in the asymptotic region, as . The elastic scattering cross section, which depends on the density of the ground-state wave function, is found to have a negligible dependence on the binding energy in this limit. The total, Coulomb and nuclear breakup cross sections are all reported to increase significantly from to 1.0 keV, and converge to their maximum values as . This increase is mainly understood as coming from a longer tail of the ground-state wave function for keV, compared to that for keV. It is also found that the effect of the continuum-continuum couplings is to slightly delay the convergence of the breakup cross section. The analysis of the reaction cross section indicates a convergence of all the breakup observables as . These results provide a better sense of the dependence of the breakup process on the breakup threshold.

Numerical modeling of spray secondary atomization with the Euler-Eulerian multi-fluid approach

This research presents numerical modeling of the spray process using the Euler-Eulerian multi-fluid approach where the standard WAVE secondary breakup model was improved and validated. The standard WAVE model tends to overestimate the creation of smaller diameter droplets in the Eulerian multi-fluid framework, which reflects as an inaccurate droplet distribution. Improvements include an introduction of probability distributions and a breakup factor into the secondary atomization model. They distribute calculated mass transfer into a number of Eulerian classes, thus alleviating the excessive creation of small diameter droplets. The model is validated by simulating the injection of high-pressured liquid fuel into the cold, non-reactive surrounding. The results are compared with experimentally obtained data of spray characteristics including spray tip penetration, spray angle, Sauter mean diameter, as well as droplet number and volume distributions. The modified model describes the spray breakup process in the Euler-Eulerian multiphase approach better than the original one.