Breakup Patterns Research Articles

A New Perspective on Dry Eye Classification: Proposal by the Asia Dry Eye Society.

:The 2017 consensus report of the Asia Dry Eye Society (ADES) on the definition and diagnosis of dry eyes described dry eye disease as “Dry eye is a multifactorial disease characterized by unstable tear film causing a variety of symptoms and/or visual impairment, potentially accompanied by ocular surface damage.” The report emphasized the instability of tear film and the importance of visual dysfunction in association with dry eyes, highlighting the importance of the evaluation of tear film stability. This report also discussed the concept of tear film–oriented therapy, which stemmed from the definition, and which is centered on provision of insufficient components in each tear film layer and ocular surface epithelium. The current ADES report proposes a simple classification of dry eyes based on the concept of tear film–oriented diagnosis and suggests that there are three types of dry eye: aqueous-deficient, decreased wettability, and increased evaporation. It is suggested that these three types respectively coincide with the problems of each layer: aqueous, membrane-associated mucins, and lipid/secretory mucin. Although each component cannot be quantitatively evaluated with the current technology, a practical diagnosis based on the patterns of fluorescein breakup is recommended. The Asia Dry Eye Society classification report suggests that for a practical use of the definition, diagnostic criteria and classification system should be integrated and be simple to use. The classification system proposed by ADES is a straightforward tool and simple to use, only through use of fluorescein, which is available even to non-dry eye specialists, and which is believed to contribute to an effective diagnosis and treatment of dry eyes.

Characteristics of tear abnormalities associated with benign essential blepharospasm and amelioration by means of botulinum toxin type A treatment.

To investigate the characteristics of tear abnormalities with benign essential blepharospasm (BEB) and the effect of botulinum toxin type A (BTX-A) treatment. Prospective and clinical study. Forty eyes of 40 patients (12 men and 28 women, ages 63.5 ±12.9) with BEB and tear abnormalities were enrolled. The average scores for subjective symptoms as evaluated by the visual analog scale (VAS) were 46.3 and Dry Eye-Related Quality-of-Life Score (DEQS) were 63.7. The fluorescein breakup time (FBUT) was 2.7 ± 1.6 sec. Among fluorescein breakup patterns (FBUPs), dimple break, with the corresponding mechanism of decreased wettability was the most frequent, observed in 29 eyes (73%). The NEI score was 0.4 ± 0.7 and the van Bijesterveld score was 0.6 ± 0.8; the Schirmer 1 test value was 13.1 ± 9.4 mm. Eighteen patients received BTX-A treatment, and significant improvement was found in severity of subjective symptoms both on VAS and DEQS as well as for FBUT. The main FBUPs changed from dimple break to random break. Tear abnormalities seen in BEB correspond to short BUT-type dry eye (DE), subclassified into decreased wettability DE in view of FBUPs.

An investigation on the impact of small-scale models in gasoline direct injection sprays (ECN Spray G)

The work presents a numerical investigation of gasoline direct injection and the resulting early development of spray plumes from an eight-hole injector (Engine Combustion Network Spray G). The objective is to evaluate the impact on the droplet size distribution (DSD) statistics from the assumed model physics, particularly for the small scales. Two modelling approaches are compared: Eulerian–Lagrangian spray atomisation with adaptive mesh refinement and a stochastic fields transported probability density function method. The two models simulate the small scales and sub-grid droplet physics with different approaches, but based on the same concept of transport of liquid surface density. Both approaches predict similar liquid distributions in the near-field comparable to experimental measurements. The spray break-up patterns are very similar and both models reproduce quasi-log-normal droplet distributions, with same overall Sauter mean diameters. The Eulerian–Lagrangian spray atomisation with probability density function approach shows different break-up behaviour between droplets originating from the dilute region and those originating from the dense core region. The transition from Eulerian to Lagrangian can be observed in the Eulerian–Lagrangian spray atomisation with adaptive mesh refinement predicted distribution with an abrupt change in the DSD. Both methods are able to produce similar DSD below filter width/grid size resolution.

Numerically simulating droplet breakup in droplet swarm using modified level set method with multi-levels

A modified level set method with multi-levels was developed to simulate the breakup behavior of multi-droplets in the turbulent flow of a pulsed disc and doughnut column. This free interface capturing method uncovered the mechanisms of three droplet breakup patterns that were observed in experiments: (1) breakup owing to shearing effect, (2) breakup because of collision with plate surfaces, and (3) breakup due to interface instability. The simulation results also indicated that the breakup frequency of 2-mm droplets increased from 0.1 to 0.6 s−1 and the breakup duration decreased from 0.025 to 0.015 s when the pulsation intensity increased from 8 to 14 mm/s. Multiple breakage occurred when the droplet size increased to 3 mm. The simulation results agreed well with our previous experimental results.

Location and pattern of non‐invasive keratographic tear film break‐up according to dry eye disease subtypes

To compare the non-invasive keratographic tear film break-up time (NIKBUT) and the location and pattern of non-invasive keratographic tear film break-up between normal group and each group of three dry eye disease (DED) subtypes. We enrolled 55 normal subjects and 250 patients with DED, who underwent tear meniscus height and NIKBUT measurements using the Keratograph® 5M. Ocular surface parameter assessments such as the fluorescein tear break-up time, ocular surface staining, Schirmer's test, and lid margin and meibomian gland examinations were performed, and the ocular surface disease index was determined. These parameters, including the proportion of the first tear film break-up location and simultaneous multiple tear film break-up pattern, were compared amongst the normal and DED subtypes. Aqueous-deficient dry eye disease (ADDE) and ADDE/meibomian gland dysfunction (MGD) subtypes showed lower NIKBUTs than those of the normal group, whilst NIKBUTs of the MGD subtype did not differ from those of the normal group. The NIKBUTs showed a good diagnostic ability in diagnosing dry eye except MGD only. The occurrence of the first tear film break-up in the central location was significantly higher in both the ADDE and ADDE/MGD subtypes, comprising approximately 40% in both subtypes (p<0.001). The proportion of a simultaneous multiple tear film break-up pattern was higher in the ADDE and ADDE/MGD subtypes, at 60.9% and 45.5%, respectively (p<0.001). The NIKBUTs and the location and pattern of non-invasive tear film break-up were different between normal group and each group of three DED subtypes.

Effects of River Geomorphology on River Ice Freeze-up and Break-up Rates Using MODIS Imagery

Evaluating driving factors of river ice freeze-up and break-up is critical for the understanding associated with river ice processes, as well as for providing a means to predict potential natural hazards of river ice formation or deformation. Spatiotemporal changes from fifteen years (2000–2015) of MODIS reflectance band 2 images were analyzed in pixel-wise linear regressions to be used as an indicator of the rates of ice freeze-up and break-up along the Slave River (Canada). The random forest algorithm was used to model the rates using river corridor slope, effective width, shape, and sinuosity as a set of predictor variables. The results reveal that the selected predictor variables can explain about 80% and 70% of the variations in ice freeze-up and break-up rates along the Slave River respectively. The slope was the most important factor in determining both freeze-up and break-up rates, followed by shape, effective width, and sinuosity. The spatiotemporal patterns of river freeze-up and ice-cover break-up obtained from the analysis of MODIS data and geomorphological variables show strong agreement with ground observations and hydrometeorological conditions along the Slave River.

Tear-film-oriented diagnosis for dry eye.

Tear-film (TF) stability protects the ocular surface epithelium from desiccation and is ensured via cooperation between the ocular surface components including constituents of the TF and ocular surface epithelium. Thus, when those components are insufficient or impaired, the TF breakup that initiates dry eye occurs. Recently, new, commercially available eye drops have appeared in Japan that enable TF stabilization via targeted supplementation of deficient ocular surface components. Hence, a new layer-by-layer diagnosis and treatment concept for dry eye, termed tear-film-oriented diagnosis and tear-film-oriented therapy (TFOD and TFOT, respectively), have emerged and become widely accepted in Asian countries and beyond. TFOD is a diagnostic method for dry eye based on the TF dynamics and breakup patterns (BUPs), through which dry-eye subtypes, including aqueous-deficient dry eye, decreased-wettability dry eye, and increased-evaporation dry eye, are diagnosed. BUPs and/or each diagnosed dry-eye subtype can, in a layer-by-layer fashion, reveal the insufficient ocular surface components responsible for the TF breakup. Using these data, the optimal topical TFOT to treat dry eye can be proposed by addressing the TF breakup via the supplementation of the insufficient components. In Japan, TF breakup is now regarded as a visible core mechanism of dry eye, and abnormal breakup time (ie, ≤ 5 seconds) and symptoms are currently considered part of the diagnostic criteria for dry eye. In this review, the importance of TF instability as a core manifestation of dry eye, the molecular mechanism of TF breakup, the concept of TFOD, and the methods for implementing TFOD for TFOT are introduced.

Direct numerical simulation of primary breakup for power-law biodiesel sprays

Abstract Biodiesel is a very promising alternative fuel in internal combustion engines. Fragmentation of the fuel injection has a fundamental influence on engine performance. The influence factors for the spray breakup process, including near nozzle fields, are still unclear. In this study, the primary of fuel sprays occurring with turbulence perturbation is devoted to simulation. The evolutionary processes of biodiesel fuels atomization affected by turbulence are investigated in present models. A validated single-phase fully developed turbulent flow is generated first to store time-varying outlet velocity database. Then, the database is mapped as the two-phase model inlet velocities boundary. A modified VOF (Volume of Fluid) coupled with DNS (direct numerical simulation) method is applied to study the evolution of fuel spray. It is found that wavy surface, ligaments, and droplets with various scales and shapes turn up gradually in jet evolution process. Meanwhile, after being sheared, distorted and stretched, different ligaments separation patterns are captured. Larger Reynolds number and higher gas densities accelerate the jet break-up process. Higher injection velocities and lower power-law indexes (n 1) fuel jet. What’s more, similar breakup patterns are detected in shear-thinning fluid (n

Breakup of finite-size liquid filaments: Transition from no-breakup to breakup including substrate effects⋆.

This work studies the breakup of finite-size liquid filaments, when also including substrate effects, using direct numerical simulations. The study focuses on the effects of three parameters: Ohnesorge number, the ratio of the viscous forces to inertial and surface tension forces, the liquid filament aspect ratio, and where there is a substrate, a measure of the fluid slip on the substrate, i.e. slip length. Through these parameters, it is determined whether a liquid filament breaks up during the evolution toward its final equilibrium state. Three scenarios are identified: a collapse into a single droplet, the breakup into one or multiple droplets, and recoalescence into a single droplet after the breakup (or even possibly another breakup after recoalescence). The results are compared with the ones available in the literature for free-standing liquid filaments. The findings show that the presence of the substrate promotes the breakup of the filament. The effect of the degree of slip on the breakup is also discussed. The parameter domain regions are comprehensively explored when including the slip effects. An experimental case is also carried out to illustrate the collapse and breakup of a finite-size silicon oil filament supported on a substrate, showcasing a critical length of the breakup in a physical configuration. Finally, direct numerical simulations reveal striking new details into the breakup pattern for low Ohnesorge numbers, where the dynamics are fast and the experimental imaging is not available; our results therefore significantly extend the range of Ohnesorge number over which filament breakup has been considered.

Numerical study of deformation and breakup of a multi-core compound droplet in simple shear flow

In this paper, we present the numerical simulation results of deformation and breakup of a multi-core compound droplet. The method used is a two-dimensional front-tracking method with a modification for multi-layer droplets. The droplet is placed at the center of the domain whose top and bottom boundaries move in the opposite directions to create the shear flow. We vary the values of various parameters in specific ranges to investigate their effects on the deformation and breakup of the multi-core compound droplet in shear flow. We mainly focus on the two-core compound droplets. Basing on the numerical results, we reveal various patterns (i.e. modes) of deformation and breakup: non-breakup types 1 and 2, breakup types 1, 2, 3 and 4. For the first non-breakup type (type 1), the outer interface is deformed with two inner droplets accumulating at the center whereas in the other non-breakup type (type 2), the inner droplets move to the two furthest ends. The non-breakup type 1 generally changes to the breakup type 4, at some critical parameters, in which the compound droplet breaks up into simple droplets at its ends with a smaller daughter compound droplet in between. The non-breakup type 2 transits to the breakup type 1 or type 2, depending on the flow conditions, with the formation of two smaller daughter compound droplets at the ends. The remaining breakup mode (type 3) is a mixed breakup mode that is a combination of the breakup types 2 and 4. These deformation and breakup patterns are mapped onto a Re–Ca diagram. We also propose some other diagrams based on the variations of the inner droplet location. In addition, we investigate the effect of the number of the inner droplets encapsulated in the compound droplet on its deformation and breakup.

Failure to validate the fluorescein breakup patterns classification in an Italian sample of dry eye patients

Failure to validate the fluorescein breakup patterns classification in an Italian sample of dry eye patients

Measurement of droplet breakage in a pump-mixer

The direct experimental data for droplet breakage frequency and daughter droplet size distribution is urgently required for the application of the population balance model. To meet this requirement, a method to directly measure the droplet breakage in the pump-mixer was developed using a high speed online camera. Two typical breakup patterns, tensile breakup and revolving breakup were observed and the number of the breakup fragments was determined. The multiple breakage was treated as a series of binary breakups. In order to precisely describe the daughter size distribution, these binary breakups were divided into three different types, i.e. the original tensile breakup, intermediate tensile breakup, and revolving breakup. The influences of the rotating speed and interfacial tension on the droplet breakup frequency and daughter droplet size distribution were then quantitatively investigated. Empirical correlations were proposed and good agreement was found between the prediction results and the experimental data.

Tear Film-Oriented Diagnosis and Tear Film-Oriented Therapy for Dry Eye Based on Tear Film Dynamics.

In December 2010 and January 2012, 3% diquafosol sodium ophthalmic solution and 2% rebamipide ophthalmic suspension, respectively, appeared first in Japan as prescription drugs for the treatment of dry eye (DE). Since then, not only the diagnosis and treatment but also the understanding of the pathophysiology of DE have greatly advanced, and a new concept of layer-by-layer diagnosis and treatment for DE, respectively termed "tear-film-oriented diagnosis" (TFOD) and "tear-film-oriented therapy" (TFOT) was born. This new concept is currently in the process of expanding from Japan to other Asian countries. TFOD is the method used for the differential diagnosis of DE, which includes aqueous-deficiency DE (ADDE), decreased wettability DE (DWDE), and increased evaporation DE (IEDE), through the dynamics of tear film (TF) and breakup patterns (BUPs) after the eye is opened. BUPs and/or each diagnosed DE subtype are/is able to distinguish the insufficient components of the ocular surface that are responsible for each BUP in a layer-by-layer fashion. Aqueous fluid, membrane-associated mucins (especially MUC16), and the lipid layer and/or secretory mucins must be insufficient in ADDE, DWDE, and IEDE, respectively, and this allows for a layer-by-layer treatment to be proposed for each BUP via the supplementation of the insufficient components, using the topical therapy currently available. In Japan, TF breakup is regarded as a visible core mechanism for DE, and an abnormal breakup time (i.e., ≤5 seconds) and symptoms are currently used for the diagnosis of DE. Therefore, TFOD and TFOT could be an ideal and practical pathway for clinicians to manage DE.

Near threshold electron-impact double ionization of helium

We examine the break-up pattern for the electron-impact double ionization of helium using a time-dependent close-coupling approach. This ionization process is one of the simplest examples of the Coulomb four-body problem of three charged particles moving in the Coulomb field of a bare nucleus. Studies of this four-body process in the near-threshold region allow exploration of the break-up dynamics, which have been stimulated by differing predictions of the most likely geometries for break-up in the related processes of triple photoionization of lithium and electron-impact double ionization of helium. While both processes lead to the same final state of three electrons moving in the field of a bare nucleus, the preferred break-up pattern at low energies for the triple photoionization is predicted as a T-shape (Emmanouilidou et al 2008 Phys. Rev. Lett. 100 063002; Colgan et al 2013 Phys. Rev. Lett. 110 063001) and for the electron-impact double ionization as a ‘triangle’ pattern (Ren et al 2008 Phys. Rev. Lett. 101 093201). Our calculations at an excess energy of 5 eV show that a triangle break-up pattern is favored, confirming earlier experimental results (Ren et al 2008 Phys. Rev. Lett. 101 093201).

Crown formation and atomization in burning multi-component fuel droplets

We report the observation of a crown-like sheet expansion and its subsequent atomization in burning multi-component fuel droplets. The droplets consisting of constituents with significant volatility differential are chosen in this study. Through homogeneous nucleation, the breakup of high-pressure vapor bubble results in the formation of radially expanding crown-like hemispherical sheet. The expansion of liquid sheet and the development of radial ligaments on its destabilized rim results in the creation of several secondary droplets. This pattern of breakup bears a close resemblance to the universally recognized Worthington-Edgerton crown configuration, which forms when a liquid droplet impact on a deep pool/thin film of same liquid or another liquid. Two distinct modes of liquid sheet fragmentation are identified during the experiments: (i) unstable sheet fragmentation and (ii) stable sheet fragmentation. In particular, the breakup characteristics of stable sheet mode is comparable to the commonly observed crown breakup by drop impingements. The modes of sheet breakup are primarily influenced by the proportion of volatile component in the mixture, which in turn dictates the onset of fragmentation and the intensity of breakup.

The evaluation of dry eye mobile apps for screening of dry eye disease and educational tear event in Japan

PurposeTo evaluate the usefulness of a dry eye mobile application (app) for screening dry eye disease (DED) at educational tear events in Japan. MethodsIn this cross-sectional study, Japanese subjects visiting a “Tears Day” event were selected randomly. They completed questionnaires and underwent ophthalmic evaluations for DED (using Japanese revised diagnostic criteria) including a functional visual acuity (FVA) test. The app calculated FVA using the average of the continuous VA over 30 s. ResultsSixty-three general-population subjects were included: 25 men and 38 women (average age, 50.8 ± 15.9 years). The prevalence of DED was 66.7% (42 subjects); age was significantly higher among subjects with DED (55.2 ± 3.4 vs. 48.1 ± 2.7 years, p = 0.04; men, 54.0 ± 7.3 vs. 47.0 ± 3.0 years, p = 0.36; women, 55.5 ± 3.9 vs. 50.6 ± 3.8 years, p = 0.4). The prevalence of DED was significantly higher in women (p = 0.04). Tear film breakup time was significantly shorter (3.8 ± 2.4 vs. 8.7 ± 2.0, p = 0.04) and the meibum score was significantly higher (p = 0.02) among subjects with DED. Regarding the tear film breakup pattern, line and random breaks were most prevalent among DED. FVA showed a significant negative correlation with DED (r = −0.25, p = 0.047). ConclusionsThe app might motivate people to perform quick tests with the expectation of getting easy DED screening. The number of subjects diagnosed with DED was relatively high.

Spray Characterization of a Slinger Injector Using a High-Speed Imaging Technique

This paper presents the experimental-visualization results of liquid breakup in a slinger injector with high-aspect-ratio radial–axial discharge channels over a range of rotational speeds between 600 and 10,000 rpm to identify detailed breakup pattern and spray characteristics. High-speed images of the jet breakup are captured and processed by a shadowgraph method. The particle/droplet imaging analysis technique is used to obtain the droplet-size distribution. Centripetal/Coriolis-induced stream-mode injection is observed for high-aspect-ratio axially canted discharge channels. The results show that the liquid-breakup process with rotational-speed values up to 4000 rpm corresponds to a subcritical stream-mode breakup. Moreover, a new phenomenon of jet bifurcation is observed at higher rotational speeds (more than 5000 rpm). Liquid-film disintegration is observed at rotational speeds of 10,000 rpm, which constitutes a transitional regime from subcritical to supercritical stream-mode breakup. The results show that the Sauter mean diameter decreases with increasing rotational speed. Furthermore, based on experimental observations, it is concluded that the number of injection orifices and their partitioning in different orientations affect the Sauter-mean-diameter values. Finally, a correlation is obtained between Sauter mean diameter, rotational speed, and volume-flow rate.

Classification of Fluorescein Breakup Patterns: A Novel Method of Differential Diagnosis for Dry Eye

To investigate the relationship between fluorescein breakup patterns (FBUPs) and clinical manifestations in dry eye cases. Cross-sectional study. In 106 eyes of 106 subjects (19 male, 87 female; mean age: 64.2 years), FBUPs were categorized into 1 of the following 5 break (B) types: area (AB, n= 19); spot (SB, n= 22); line (LB, n= 24); dimple (DB, n= 19); random (RB, n= 22 eyes); and dry eye-related symptoms using the visual analog scale (VAS, 100mm= maximum), tear meniscus radius (TMR, mm), tear film lipid layer interference grade (IG) (grades 1-5; 1= best) and spread grade (SG) (grades 1-4; 1= best), tear film noninvasive breakup time (NIBUT, seconds), fluorescein breakup time (FBUT, seconds), corneal-epithelial damage (CED) score (15 points= maximum), ocular surface epithelial damage (OSED) score (9 points= maximum), and the Schirmer 1 test (ST1, mm) were examined and compared between each FBUP. In each FBUP, eye dryness and fatigue were the severest symptoms. Characteristic symptoms were sensitivity to light, heavy eyelids, pain, foreign body sensation, difficulty opening the eye, and discharge for AB, heavy eyelids for SB, and foreign-body sensation for LB. Statistically significant differences were found in TMR (AB-SB, -DB, and -RB; LB-RB), IG (AB-all other FBUP; LB-SB and -DB), and SG (AB-all other FBUPs), FBUT (AB-LB, -DB, and -RB; SB-DB and -RB; LB-RB; DB-RB), and NIBUT (AB-all other FBUPs; SB-DB and-RB, and LB-RB), CED (AB-all other FBUPs; LB-SB, -DB, and -RB) and OSED (AB-SB, -LB, and -DB; LB-SB,-DB, and -RB), and ST1 (AB-SB, -DB, and -LB) (P< .05 in each comparison). The 5 different FBUPs constituted different groups, reflecting different pathophysi-ologies.

Experimental and computational study on jet final depth under coolant jet-melt interaction

ABSTRACTPouring coolant into molten material provides an efficient method for cooling molten core debris in light water reactor. This coolant jet-melt interaction mode needs to be studied for proposed application and safety concern. The jet breakup pattern and its final depth are crucial factors for efficient cooling. In the present study, the hydraulic penetration behavior of coolant jet is investigated using experimental and numerical approaches. A series of visual experiments are conducted using low-density gasoline as coolant jet and high-density water as molten fuel. The images of jet behaviors and the data of gasoline jet penetration depth are obtained and analyzed. Based on FLUENT15.0 a 3D axisymmetric model is built and Volume of Fluid (VOF) method is used. The hydraulic penetration behaviors of jet and final penetration depth are correctly simulated and analyzed. The fluctuating phenomenon of penetration depth and the effects of various parameters are discussed. Jet velocity and density ratio are key factors to final penetration depth. The conclusions are helpful to understand the parameter influence and the fluctuation mechanism of final penetration depth and substantiate the understanding of the coolant jet hydraulic penetration behavior during coolant jet-melt interaction.

Details on the Mechanism of High-Frequency Swirl Coaxial Self-Pulsation

In this paper, lower boundaries at which a liquid-centered swirl coaxial injector switches from nonpulsatile behavior to self-pulsation are experimentally resolved under water and air flow conditions for an element configured both with and without inner post recess. Data-based modal decomposition analyses are used to extract distinct near-field spray dynamics from high-speed schlieren imagery. Self-pulsation is found to be instability-induced by gas–liquid interactions that strip liquid from the contiguous spray cone. These interactions take place in a regime where coaxial flows are known to experience fiber-type breakup due to hydraulic and aerodynamic instabilities. Periodic, nonpulsatile spray breakup patterns are detected as a precursor to self-pulsation. The frequency of these nonpulsatile patterns ranges from and compares well with the frequency of self-pulsation at its onset, which directly supports conventional ideas related to the mechanism of self-pulsation. The transition of spray dynamics from nonpulsatile to self-sustained oscillations shows a destabilizing/stabilizing effect as gas velocity increases, establishes temporally unstable spray oscillation at onset, and suggests that self-pulsation may be excited when stripping behavior engages one or more fluid oscillators of the injector element.