Breakup Patterns Research Articles

Evolution of liquid film in a crossflow tunnel: liquid film thickness measurement and effect of droplet impingement on film breakup

Abstract Liquid jet in crossflow tunnel has widespread applications in various industrial devices,
with the measurements of liquid film on the bottom surface pivotal in exploring relevant mechanisms
such as heat transfer and film breakup. This work reports the measurements of liquid film on the
bottom surface of a crossflow tunnel using the brightness-based laser induced fluorescence (LIF)
method under different flow conditions at ambient pressure and temperature. Film breakup
phenomena are observed downstream within the tunnel. Employing the shadowgraph method, two
distinct patterns of film breakup associated with the droplet impingement positions on the film wave
are identified, i.e., bag breakup and membrane breakup. The film thickness is subsequently calculated,
and jet impingement and spray impingement of injected liquid on tunnel bottom surface are classified
based on the centerline film thickness. A critical jet-to-crossflow momentum flux ratio (q) is determined to be proportional to the square of tunnel height. The averaged film thickness across the entire cross-section downstream at a distance of 50 mm from the nozzle is found to increase with the logarithm of q. Besides, the film boundaries are also identified under different flow conditions, which can be well predicted by a quadratic fit with the fitting parameters also correlated to the logarithm of q.

Application of RiTiCE in understanding hydro-meteorological controls on ice break-up patterns in River Tornionjoki

The Arctic region experiences significant annual hydrologic events, with the spring flood and ice break-up being the most prominent. River ice break-up, in particular, poses high socioeconomic and ecological expenses, including morphological changes and damage to riverine structures. This study aims to investigate the spatiotemporal patterns of river ice in the River Tornionjoki, including the timing of ice break-up at different latitudes. We utilized observation data and remote sensing techniques to track changes in ice patterns overtime on the River Tornionjoki. The study indicates that the ice break-up in the River Tornionjoki basin typically occurs during Apr-Jun based on the reach location in different latitudes; therefore, different stations behave according to their latitudinal location. We observed significant spatial variations in ice break-up timing across the basin, with an earlier break-up in the lower latitudes compared to the upper latitudes. The average ice break-up day in lower latitude stations ranges between 200–205, while in higher latitude stations the average ice break-up day ranges between 215–228.

Experiment study on adhesion dynamic characteristics of droplet impacting on an inclined heated surface

The behaviors and mechanisms of droplet impact on an inclined heated surface is of great importance. In this work, an experimental platform for the droplets impact on the surfaces with different inclined angles and temperatures was established to study the various impact patterns and dynamics. The impact pattern, sliding distance, lengths at the leading and trailing edge points and maximum spreading factor were studied in detail. The results show that the impact patterns were classified as adhesion, splash, rebound and breakup patterns. In the adhesion pattern, a sliding distance model was developed based on Newton's second law and force analysis that considered the viscous, adhesion and gravitational forces for different angles. Larger angle promotes length of the leading edge point, inhibits length of the trailing edge point. Higher temperature suppresses the length of the trailing edge point by boiling. In addition, a model for the maximum spreading factor of the inclined surface was developed by combining a spreading prediction mode with an energy conservation equation, which incorporates kinetic, surface and dissipation energies. An increase in the normal Weber number suppresses the maximum spreading factor. Temperature has a different effect on the maximum spreading factor depending on the normal Weber number.

Behind the Non-Uniform Breakup of Bubble Slug in Y-Shaped Microchannel: Dynamics and Mechanisms.

Bubble flow in confined geometries is a problem of fundamental and technological significance. Among all the forms, bubble breakup in bifurcated microchannels is one of the most commonly encountered scenarios, where an in-depth understanding is necessary for better leveraging the process. This study numerically investigates the non-uniform breakup of a bubble slug in Y-shaped microchannels under different flow ratios, Reynolds numbers, and initial bubble volumes. Overall, the bubble can either breakup or non-breakup when passing through the bifurcation and shows different forms depending on flow regimes. The flow ratio-Reynolds number phase diagrams indicate a power-law transition line of breakup and non-breakup. The bubble takes longer to break up with rising flow ratios yet breaks earlier with higher Reynolds numbers and volumes. Non-breakup takes less time than the breakup patterns. Flow ratio is the origin of non-uniform breakup. Both the Reynolds number and initial volume influence the bubble states when reaching the bifurcation and thus affect subsequent processes. Bubble neck dynamics are analyzed to describe the breakup further. The volume distribution after breaking up is found to have a quadratic relation with the flow ratio. Our study is hoped to provide insights for practical applications related to non-uniform bubble breakups.

Numerical simulation study of bubble breakup mechanism in microchannels with V-shaped obstacle

Microfluidic gas-liquid two-phase flow in microchannels plays a crucial role in diverse applications, from electronics cooling to biomedical engineering. Precisely controlling microbubble formation and breakup is essential for industrial microfluidic processes. This study investigates microbubble breakup in microchannels with V-shaped obstacles. Four breakup patterns are identified: no breakup, breakup with permanent gaps, breakup with partly obstruction, and breakup with permanent obstruction. The bubble breakup with permanent obstruction could maintain a wider flow pattern range. The bubble breakup process is categorized into three stages: squeezing, transition, and pinch-off. We observe power-law relationships between bubble characteristics and dimensionless time in each stage, and the impact of the capillary number Ca and liquid phase viscosity μL on bubble properties. This research deepens our understanding of gas-liquid two-phase flow in microchannels with obstacle structures and is relevant to analytical chemistry and fine chemical engineering applications.

COMPARISON OF TEAR FILM BREAKUP PATTERN IN ACTIVE AND INACTIVE THYROID EYE DISEASE PATIENTS

Abstract
 Introduction & Objectives : Thyroid Eye Disease (TED) is an autoimmune inflammatory disease of the orbit that affects orbital fat, extraocular muscles, periocular tissue and lacrimal glands. TED activity can be assessed with a Clinical Activity Score (CAS) to identify active or inactive TED conditions. Dry Eye Diseases (DED) is one of the manifestations in patients with TED with a prevalence that varies from 27%-96%. The Asia Dry Eye Society (ADES) 2017 proposed a new concept for DED diagnosis and therapy, namely Tear Film Oriented Diagnosis (TFOD) and Tear Film Oriented Diagnosis Therapy (TFOT) with Tear Film Breakup Pattern (TBUP) examination. TBUP examination help in determine specific management of DED. The aim of this study is to determine the differences in TBUP in TED patients based on active and inactive.
 Methods : This is an analytical observational study with a cross-sectional design. The subjects were TED patients who came to the Cicendo Eye Hospital and met the inclusion criteria. The study was conducted at the National Eye Center of Cicendo Eye Hospital in April - June 2022. The data were analyzed with the Chi-Square Test.
 Results : This study was conducted on 23 patients or 46 eyes. This study found a statistically significant differences in TBUP features in active and inactive TED patients (p=0.0001). The most common features of TBUP was found in active TEDs was dimples (55%).
 Conclusion : There are differences of TBUP features in active and inactive TED patient.

COMPARISON OF TEAR FILM BREAKUP PATTERN IN ACTIVE AND INACTIVE THYROID EYE DISEASE PATIENTS

Introduction: Thyroid Eye Disease (TED) is an autoimmune inflammatory disease of the orbit that affects orbital fat, extraocular muscles, periocular tissue and lacrimal glands. TED activity can be assessed with a Clinical Activity Score (CAS) to identify active or inactive TED conditions. Dry Eye Diseases (DED) is one of the manifestations in patients with TED with a prevalence that varies from 27%-96%. The Asia Dry Eye Society (ADES) 2017 proposed a new concept for DED diagnosis and therapy, namely Tear Film Oriented Diagnosis (TFOD) and Tear Film Oriented Diagnosis Therapy (TFOT) with Tear Film Breakup Pattern (TBUP) examination. TBUP examination help in determine specific management of DED. The aim of this study is to determine the differences in TBUP in TED patients based on active and inactive. Methods: This is an analytical observational study with a cross-sectional design. The subjects were TED patients who came to the Cicendo Eye Hospital and met the inclusion criteria. The study was conducted at the National Eye Center of Cicendo Eye Hospital in April - June 2022. The data were analysed with the Chi-Square Test. Result: This study was conducted on 23 patients or 46 eyes. This study found a statistically significant differences in TBUP features in active and inactive TED patients (p=0.0001). The most common features of TBUP was found in active TEDs was dimples (55%). Conclusion: There are differences of TBUP features in active and inactive TED patient.

Experimental investigation and theoretical prediction of droplet breakup under a combined electric field and shear flow field

The electrohydrodynamic breakup of a droplet under a combined electric field (EF) and shear flow field (SFF) is experimentally investigated. The interface morphology characteristics of the droplet undergoing different breakup patterns are analyzed, and the interactions among electric forces, viscous forces, and interfacial tension during the droplet breakup process are also revealed. In addition, a diagram of droplet breakup patterns with different hydrodynamic and electric capillary numbers (Ca and CaE, respectively) is summarized. In particular, a prediction model for the criteria of droplet breakup under combined EF and SFF is proposed. The results indicate that three typical patterns of droplet breakup occur in turn with increasing CaE, i.e., satellite droplet detachment from a migrating droplet, a lobe detachment pattern, and a lobe disintegration pattern. As the Ca increases, the breakup pattern of satellite droplets detaching from the migrating droplet gradually disappears, and the critical CaE for droplet breakup decreases because the enhanced viscous force facilitates the detachment of the lobes from the mother droplet. Additionally, the breakup pattern of charged lobe disintegration occurs under a large CaE when the charge of the droplet reaches the Rayleigh limit. The critical CaE of the lobe disintegration breakup pattern decreases first and then increases with increasing Ca because the changes in droplet shape, interfacial tension, electrical potential energy, and fluid potential energy lead to a variation in the Rayleigh limit. Moreover, the breakup speeds of the three patterns are also altered by the strengths of the SFF and EF. Particularly, a reliable prediction model for the criterion of droplet breakup is proposed and compared with experimental data. This model provides a feasible approach for determining the criterion of droplet breakup through a very small amount of data for droplet-based applications.

Numerical investigation of nozzle length effects on Rayleigh jet breakup behaviors and droplet formation properties at different modulation amplitudes in liquid droplet radiator

Uniform droplet stream generation is required for a liquid droplet radiator to achieve the efficient heat dissipation of space nuclear power systems. In this study, Rayleigh jets breaking into continuous droplet streams at different modulation amplitudes are numerically simulated to investigate the nozzle length effects on jet breakup behaviors and droplet formation properties. First, simulated results confirm that the growth of secondary instability wave on jet free-surface causes the jet breakup pattern transition from downstream pinching to upstream pinching. As the modulation amplitude is from 0.04 up to 0.16, the nozzle length range where the upstream pinching occurs in the jet breakup is broadened from null to 1–5. The essential reason for the increase of jet breakup length is the reduction of fundamental amplitude and the increase of full velocity relaxation length. Then, a comprehensive prediction model for the velocity-modulated jet breakup length is developed in agreement with the experiments, and the average relative error is below 7.38 %. Finally, two types of satellite droplet formation regimes including rear-merging and forward-merging satellite droplets are identified by the oscillation mode of the jet tip. It is found that the primary droplet generation frequency is equal to the external disturbance frequency and independent of nozzle length and modulation amplitude. Increasing the nozzle length and modulation amplitude can both increase the satellite droplet diameter and primary droplet spacing, while the primary droplet diameter is almost constant at around 1.85.

Artificial Intelligence in Dry Eye Disease: Benefits, Challenges and Future Directions

Current Diagnostic Challenges in Dry Eye Disease Dry eye disease (DED) is a challenging condition to pin down, given the various probable aetiologies, signs, and symptoms. DED is characterised by its loss of tear-film homeostasis, ocular surface inflammation, hyperosmolarity, eye discomfort, and visual abnormalities [1]. However, the signs of DED are occasionally inconsistent with the symptoms stated by patients [1]. There is presently no one clinical test that can uniformly pinpoint DED [1]. DED is diagnosed using a variety of subjective tests and symptom questions, including tear breakup time (TBUT), Schirmer's test (ST), fluorescein and lissamine green staining of the corneal (CSS1) and conjunctival surface (CSS2), and the ocular surface disease index (OSDI) [1]. Furthermore, the differentiation of different tear film breakup patterns is thought to be at the centre of a tear film-oriented diagnosis, which helps elucidate the pathophysiology of DED (i.e., identify the insufficient component of the tear film or of the corneal surface epithelium responsible for TFBU), sub classify DED, and select the optimal topical therapy (decide on the most appropriate treatment) [2]. Additionally, although meibomian gland dysfunction (MGD) is the leading cause of evaporative DED and one of the most common conditions encountered in DED, diagnosing MGD can be difficult due to the non-specific nature of the symptoms and great inter-examiner variability in grading clinical variables associated with MGD [3]. As a result, standardised and universal diagnostic and decision-making tools in DED are highly valued. Artificial intelligence (AI) through machine learning (ML) and deep learning (DL) has garnered attention in the ophthalmological field, particularly in the screening and diagnosis of retinal and optic nerve conditions [4]. These AI algorithms perform imageintensive analyses on fundus or optical coherence tomography (OCT) images [4]. Similarly, in the current practices of DED, AI is expected to facilitate the data-intensive analysis of DED signs and symptoms when diagnosing, triaging, and managing DED patients.

A volume of fluid based method for consistent flux computation in large-density ratio two-phase flows and its application in investigating droplet bag breakup behavior

This article introduces a novel method for computing consistent fluxes, which enables highly robust simulations of two-phase flow problems characterized by large-density ratios. The approach is based on the geometric reconstruction volume of fluid method and utilizes a staggered grid implementation. This allows for accurate and robust simulation of phenomena like droplet bag breakup in flows with intense velocity shear and significant density differences. Through numerical experiments, it has been demonstrated that this method can reliably simulate two-phase flows with large-density ratios while preserving excellent energy conservation properties. Expanding on these findings, the researchers have developed a solver that leverages block-structured adaptive mesh to perform high-fidelity simulations of droplet bag breakup scenarios. Remarkably, this solver accurately reproduces three distinct breakup patterns: bag mode, stamen mode, and sheet-stripping mode. A comprehensive analysis has also been conducted by comparing the dimensionless maximum cross-stream radius with experimental test results. Furthermore, the study investigates the kinetic energy spectrum of fully developed two-phase turbulence under different droplet generation mechanisms and examines the distribution of droplet sizes. The numerical results validate the efficacy and reliability of this method in accurately simulating two-phase flows characterized by significant density disparities and interface momentum exchange.

Dry Eye Subtype Classification Using Videokeratography and Deep Learning.

We previously reported on 'Tear Film Oriented Diagnosis' (TFOD), a method for the dry eye (DE) subtype classification using fluorescein staining and an examination of fluorescein breakup patterns via slit-lamp biomicroscopy. Here, we report 'AI-supported TFOD', a novel non-invasive method for DE subtype classification using videokeratography (VK) and "Blur Value" (BV), a new VK indicator of the extent of blur in Meyer-ring images and deep learning (DL). This study involved 243 eyes of 243 DE cases (23 males and 220 females; mean age: 64.4 ± 13.9 (SD) years)-i.e., 31 severe aqueous-deficient DE (sADDE) cases, 73 mild-to-moderate ADDE (m/mADDE) cases, 84 decreased wettability DE (DWDE) cases, and 55 increased evaporation DE (IEDE) cases diagnosed via the fluorescein-supported TFOD pathway. For DL, a 3D convolutional neural network classification model was used (i.e., the original image and BV data of eyes kept open for 7 s were randomly divided into training data (146 cases) and the test data (97 cases), with the training data increased via data augmentation and corresponding to 2628 cases). Overall, the DE classification accuracy was 78.40%, and the accuracies for the subtypes sADDE, m/mADDE, DWDE, and IEDE were 92.3%, 79.3%, 75.8%, and 72.7%, respectively. 'AI-supported TFOD' may become a useful tool for DE subtype classification.

Correlation Between the Severity of Dry Eye Disease and Fluorescein Break-Up Patterns (FBUP)

Dry eye disease is a disorder of the eye surface characterized by instability of the tear film. The FBUP examination is one of the examinations used to determine the stability of the tear film. The various symptoms that occur in each type of dry eye indicate differences in break-up patterns (BUP). This study aims to determine the correlation between the severity of dry eye disease and the appearance of FBUP at RSUP dr. Mohammad Hoesin Palembang. A correlative analytical cross-sectional study was undertaken at the Eye Polyclinic, Infection- Immunology Subdivision, Dr. Mohammad Hoesin General Hospital Palembang from January to June 2022. There were 32 patient samples with 60 dry eye samples that met the inclusion criteria. The correlation between the Schirmer Test, TBUT and the severity of dry eye disease with the appearance FBUP was analyzed using the Spearman Rho's test. All data were analyzed with SPPS version 23.0. In this study, the results showed that there was a moderate and significant positive correlation between the degree of the Schirmer test and the appearance FBUP (r = 0.482; p = 0.000) and a moderate and significant positive correlation between the TBUT degree and the appearance FBUP (r = 0.435; p = 0.001) . In addition, the results showed that there was a moderate and significant positive correlation between the severity of dry eye disease and the appearance of FBUP (r = 0.478; p = 0.000). Using the multivariate test, it was concluded that the degree of dry eye was statistically significantly related to age (p = 0.001) and gender (p = 0.001). There is a correlation between the severity of the disease and the appearance FBUP of patients with dry eye disease.

A Comprehensive Assessment of Tear-Film-Oriented Diagnosis (TFOD) in a Dacryoadenectomy Dry Eye Model.

Tear film instability is a major cause of dry eye disease. In order to treat patients with short tear film breakup time (TBUT)-type dry eye, the development of tear film stabilizing agents is essential. However, the lack of an appropriate animal model of tear film instability has made drug development difficult. Although rabbit dry eye models have been reported in the past, there are only a few reports that focus on tear film instability. Herein, we assessed the tear film stability of a rabbit dry eye model induced by dacryoadenectomy. A clinical evaluation of the ocular surface, interferometry, and histological assessments of the cornea and conjunctiva were performed. Following the removal of the lacrimal glands, TBUT was shortened significantly, with dimple and random breakup patterns prominently observed. Furthermore, the blink rate in this model increased after dacryoadenectomy, suggesting that this model partially captured the phenotypes of human short TBUT-type dry eye and may be useful as an animal model for investigating potential drug candidates.

The unique properties of tear film breakup process in patients with nasal unilateral pterygium.

This study found that the unique properties of tear film breakup process in eyes with pterygium, combined with ocular surface parameters, further revealed specific dynamic mechanism. It suggested that the thickness of pterygium was especially valuable in deciding the necessity of surgical management. This study aimed to explore the dynamic mechanism of tear film instability in eyes with pterygium. A paired-eye controlled cross-sectional study was conducted. Seventy-eight patients with nasal pterygium were enrolled. Fluorescein tear film breakup was observed. Several key parameters related to tear film quality were defined and analyzed, including total breakup area (mathematically derived from pixel size using MATLAB), breakup velocity, fluorescein breakup time, breakup location and pattern, tear meniscus height, score of fluorescein corneal staining, and meiboscore. With comparable tear meniscus height, score of fluorescein corneal staining, and meiboscore between paired eyes (p > 0.05), eyes with pterygium had shorter breakup time, larger breakup area, and faster breakup velocity (p < 0.05). In eyes with pterygium, a positive correlation between meiboscore and pterygium parameters including length, thickness, and size was observed (p > 0.001). As the thickness increased, difference of breakup time and area between paired eyes increased (p = 0.02 and 0.046). Eyes with pterygium had more fixed inferonasal breakup location and often presented as dimple break (60%), whereas random break was the most common in contralateral normal eyes (62%). A unique breakup pattern named pterygium-induced local dimple break was found. It displayed as an irregular but vertical line-like shape appearing after lipid layer spreading, which was adjacent to the lower margin of pterygium and presented with unique properties including inferonasal breakup location, local breakup area, shorten breakup time, and faster breakup velocity. Eyes with pterygium showed a unique tear film breakup process and novel breakup pattern named pterygium-induced local dimple break . Dynamic mechanism played a significant role in tear film instability of eyes with pterygium rather than aqueous deficiency and increased evaporation.

Examining the influence of microclimate conditions on the breakup of surface‐based temperature inversions in two proximal but dissimilar Yukon valleys

AbstractSurface‐based temperature inversions (SBIs) are frequent and strong in valleys of north‐central Yukon, which drive annual average surface lapse rates that are strongly inverted (≤1.19°C 100 m−1) within the first 100 to 150 vertical meters. This study aims to test the relationship of SBI breakup with local microclimate factors determining the influence on surface lapse rate breakup patterns. A field study was conducted using elevational transect analysis. SBI breakup in the non‐winter season had a strong relationship between the diurnal cycle of increased solar radiation, warming of the surface, and development of atmospheric turbulence in the form of increased wind speed. SBIs during these non‐winter seasons had a peak breakup time of 4 to 8 h following sunrise. Wintertime SBIs often persisted past the diurnal cycle and broke up independent of solar radiation, contributing significantly to the inverted average surface lapse rates. Mechanisms of SBI breakup during the winter are likely more synoptic in nature and one possible mechanism could be shallow cold air flows. Current classification of SBI duration as persistent or transient was reviewed and adjusted, and SBIs with a duration of 18 to 22 h were removed due to the breakup of those events being related to the diurnal cycle.

Understanding Deformation and Breakup Tendency of Shear-Thinning Viscoelastic Drops in Constricted Microchannels.

The study of drop deformation in response to various stresses has long piqued the interest of several academics. The deformation behavior of cells, drug carriers, and even drug particles moving via microcapillaries inside the human body can be modeled using a viscoelastic drop model. A drop breakup study can also provide better design guidance for nanocarriers that can deliver on-demand burst drug releases at specific cancer sites. Thus, we attempted to investigate the deformation and breakup of a shear-thinning finitely extensible nonlinear elastic-peterlin (FENE-P) drop moving through the constricted microchannel. The computational simulation suggested that drop deformation and breakup can be manipulated by varying of parameters like channel confinement, Deborah number, solvent viscosity ratio, viscosity ratio, and capillary number. We attempted to find the critical capillary number for initiation of drop breakup. Observations from present study will give valuable insights into deformation and breakup patterns of drug carriers inside constricted microcapillaries. The simulations of the two-phase viscoelastic drop─Newtonian matrix system were performed on an open-source solver, Basilisk.

Vortex ring and bubble interaction: Effects of bubble size on vorticity dynamics and bubble dynamics

Bubbly turbulent flows involve complex interactions between bubbles and vortices, in which their size ratio plays a critical role. The present work investigates an idealization, namely, the interaction of a single air bubble with a (water) vortex ring, with the focus being on the effects of the bubble-to-vortex core size ratio (Db/Dc,o) on the bubble and ring dynamics (Db = bubble diameter and Dc,o = initial vortex core diameter). The interaction is studied for size ratio, Db/Dc,o, of 0.6–1.7, over a large Weber number range from 10 to 500 [We=0.87ρ(Γ/πDc,o)2/(σ/Db), Γ = circulation]. On the bubble dynamics side, in the initial stages of the interaction after the bubble's capture by the ring, the bubble's radial equilibrium position, its azimuthal elongation, and breakup pattern are influenced by both Db/Dc,o and We. However, at longer times, the results show that the We alone decides the broken bubbles to Db ratio and scales as We−0.13, which can be contrasted with the scaling of We−0.6 in isotropic turbulence [R. Shinnar, J. Fluid Mech. 10, 259–275 (1961)]. On the ring dynamics side, increasing Db/Dc,o leads to larger deformation of the vortex ring core at low We, and these effects are significant above a critical Db/Dc,o of about 1.2. Under these conditions, the vortex core can fragment, leading to large reductions in the ring's measured convection speed and axial enstrophy, both of which follow a similar scaling, (Db/Dc,o)2/We; the reduction in enstrophy being reminiscent of bubbly turbulent flows. These results and scalings should help us to better understand and model bubble–turbulence interactions.

A comprehensive field investigation of the dynamic break-up processes on the Chaudière River, Quebec, Canada

Abstract The Chaudière River in Quebec, Canada, is well known for its frequent ice jam flooding events. As part of a larger watershed research program, an extensive field campaign has been carried out during the 2018–2019 and 2019–2020 winter seasons to quantify the spatiotemporal characteristics of the break-up processes along the Chaudière River. The results showed that mid-winter ice jams have formed in the Intermediate Chaudière and persisted until spring break-up. Spring break-ups were initiated in the Upper Chaudière, and then, almost simultaneously, in the Intermediate and Lower Chaudière reaches. The break-up in the Intermediate Chaudière usually lasts longer than the rest of the river since the slope is much milder, and the occurrence of mid-winter ice jams has been seen to delay the ice clearing. A reach-by-reach characterization of the cumulative degree day of thawing and discharge thresholds for the onset of break-up has been identified. During the field campaign, 51 ice jams were documented together with their location, length, date of formation, and the morphological feature triggering jam formation. Break-up patterns, hydrometeorological thresholds of ice mobilization, and ice jam sites identified in this study can serve as a basis for the implementation of an early warning system.

Statistical Characterization of Bubble Breakup Flow Structures in Swirl-Type Bubble Generator Systems

The bubble breakup pattern on a swirl-type bubble generator (MBG) with water and air fluids was experimentally studied. The bubble breakup pattern was analyzed visually and characterized using several parameters such as Pressure Drop (∆P), Kolmogorov Entropy, Standard Deviation, and DWT (Discrete Wavelet Transform), which were taken from the extraction of pressure signals at the water inlet and outlet of the bubble generator. The wavelet spectrum of the measured signal was shown to identify the overall bubble breakup pattern, and the wavelet variance vector is proposed as a character vector to identify the bubble breakup pattern. The results show that there were three types of different flow breakup patterns: (1) static breakup, (2) dynamic breakup, and (3) tensile breakup. The observed bubble breakup sub-patterns can be categorized into tensile, moderate tensile, high tensile, dynamic, low dynamic, static, and high static sub-patterns. The static clustered breakup pattern has the highest wavelet energy compared to the tensile and dynamic clustered breakup.