Big Bubble Research Articles

Scaling laws for mitigated pile driving: Dependence of underwater noise on strike energy, pile diameter, ram weight, water depth, and mitigation systema).

Sound induced by impact pile driving is a possible risk to marine life. Therefore, it is common practice to use noise mitigation systems during piling to reduce the respective impact and to fulfill the prescribed noise limits. Scaling laws for the estimation of the underwater noise from unmitigated impact pile driving have been presented in von Pein, Lippert, Lippert, and von Estorff, "Scaling laws for unmitigated pile driving: Dependence of underwater noise on strike energy, pile diameter, ram weight, and water depth," Appl. Acoust. 198, 108986 (2022). This contribution shows how these scaling laws need to be changed if noise mitigation systems are considered. Scaling laws are developed for four different kinds of noise mitigation system setups. These include big bubble curtains, double big bubble curtain combinations, a fully absorbing system directly at the pile, and the combination of a system close to the pile and a double big bubble curtain. The derived scaling laws are verified and compared to publicly available measurement data.

Tomographic and topographic predictive factors of big bubble formation during deep anterior lamellar keratoplasty in keratoconus

PurposeTo identify preoperative predictors of big bubble (BB) formation during deep anterior lamellar keratoplasty (DALK) in patients with keratoconus (KC).MethodsDesignRetrospective cohort study in an Italian tertiary centre.Study populationConsecutive patients with...

Influence of Opacity Depth on Big Bubble Formation During Deep Anterior Lamellar Keratoplasty in Corneal Stromal Scars.

To identify the key preoperative predictors of big bubble (BB) formation during deep anterior lamellar keratoplasty in patients with corneal stromal scars (CSS). This retrospective cohort study included consecutive patients with CSS after infective keratitis who underwent BB-deep anterior lamellar keratoplasty between January 2021 and July 2023 at a tertiary referral center. Topographic and tomographic data were collected to compare the rates and types of BB formations. Anterior segment optical coherence tomography (AS-OCT) was employed to assess the maximum depth of opacity by dividing the stroma into 3 zones of equal thickness: anterior (stage A), mid (stage B), and posterior stroma (stage C). Multivariate logistic regression analysis was performed to identify the potential preoperative predictors of bubble formation. Pneumatic dissection was achieved in 13 of 33 eyes (39.4%), with 11 BB type 1 eyes (33.3%) and 2 BB type 2 eyes (6.1%). According to AS-OCT grading, bubble formation was more frequent with CSS involving more superficial stromal layers (P <0.032). In the eyes with stage C, bubble formation failed 12 out of 14 times (85.7%, P <0.026). Spearman correlation showed that bubble formation was inversely associated with the AS-OCT grading (rho = -0.443, P = 0.001). After logistic regression analysis, AS-OCT grading was found to be the sole factor that predicted bubble formation (coeff. -1.58, confidence interval 95% -3.03 to -0.12, P = 0.034). Depth of opacity in CSS was the key determinant for predicting the success of pneumatic dissection, as advanced AS-OCT stages are strongly associated with BB failure.

One-Step Intraoperative Optical Coherence Tomography Guided Tunnel, Mushroom Femtosecond Laser Big Bubble Deep Anterior Lamellar Keratoplasty.

The aim of our study is to investigate the feasibility and outcomes of using a femtosecond laser (FSL) platform (Ziemer LDV Z8) for deep anterior lamellar keratoplasty (DALK), enabling the creation of mushroom-shaped graft-host junctions, lamellar cuts, and intrastromal tunnels, to facilitate the big bubble, in one step. We included wet lab experiments on nine porcine eyes to assess the laser accuracy and cuts depth using an anterior segment (AS) OCT. This was followed by an interventional prospective case series on 10 eyes with variant corneal pathologies. The Z8 system, with in-built intraoperative optical coherence tomography (iOCT), guided corneal scans and directed the cuts. ASOCT showed visible mushroom configurations, lamellar cuts, and tunnels. Deviations from the target were 1.6%, 2.6%, and 3.5%. Anterior lamellar removal was easy in all clinical cases, including corneal scarring. The intrastromal tunnel was found at the preset location and the mushroom configuration was acquired. A big bubble was achieved in all cases. Type 1, 2, and 3 bubbles were formed in eight, one, and one case, respectively. We describe a new approach to DALK in which the in-built iOCT-guided FSL enables safe, precise, controlled, and reproducible desired cuts in one step. The preliminary clinical outcomes were favorable.

Production of ultrafine particles with nanometer size distribution via a bubble film bursting method

Producing particles smaller than 50 nm continues to be a challenge for commonly used atomization techniques. In the present study, an atomization method based on bubble film bursting was proposed to generate ultrafine nanoparticles. The atomization solution added with surfactant was converted to big bubble with thin film, and three needles were employed to puncture the bubbles to produce small droplets. Droplets formed ultrafine nanoparticles after being dried by a diffusion dryer. The results showed that the median diameter of particles generated by bubble film bursting could be as low as 30 nm. The thinness of the bubble film played a significant role in producing small droplets. Additionally, the size distribution of particles was influenced by the NaCl concentration and the distance of the needle to orifice, as they altered the thickness of the bubbles. The bubble film bursting atomization method offers the advantage of producing ultrafine particles and holds potential for application in various fields.

Deep anterior lamellar keratoplasty in advanced keratoconus in children: A 4-year study

Purpose: The purpose of the study was to evaluate the outcomes of deep anterior lamellar keratoplasty (DALK) in children and adolescents with advanced keratoconus (KC) at a tertiary eye care center in India. Design: This was a retrospective cross-sectional study. Methods: All cases of KC under the age group of 18 years, operated for DALK at a tertiary eye care center in South India, were evaluated from January 2018 to January 2022; outcome measures were best-corrected visual acuity (BCVA), graft clarity at final follow-up, and complications. Results: Of 27 eyes of 25 cases, 16 were male and 9 were female, with a mean age of presentation at 14.9 years. In stromal dissection technique, big bubble was attempted in 23 eyes and achieved in 20 eyes; manual dissection was done for the rest of the cases. Final BCVA varied from 0.1 to 0.6 logMAR units. Twenty-three eyes had excellent graft clarity at final follow-up. Complications noted in the study were intraoperative microperforation in four cases, postoperatively suture-related complications in three cases, and corneal graft rejection in one case. Conclusion: DALK in pediatric age group for advanced KC is an effective treatment option.

Study on characteristics of gas–liquid two-phase flow in pump as turbine using multiple-size group model

The multi-size group (MUSIG) model is employed in this paper to simulate the gas–liquid two-phase flow in pump as turbine (PAT) since the traditional Eulerian–Eulerian two-fluid model is unable to take into account the phenomena of breakup and coalescence of bubbles. First, the simulation of gas–liquid two-phase flow in a square column is compared with the experiment to verify the accuracy of the MUSIG model. Then, the results of gas–liquid two-phase flow in PAT simulated by the MUSIG model are compared with those by the conventional uniform bubble (UB) model and find that the MUSIG model is more favorable to capture the flow pattern at high gas content compared to the UB model. Based on the MUSIG model, the internal flow characteristics, pressure fluctuation, and bubble size distribution of the PAT are analyzed. The rotation of the blades breaks a part of big bubbles into small bubbles in the volute, resulting in a smaller diameter of the bubbles entering the impeller. As the gas content increases, the number and size of vortices in the impeller flow channel increase. The vortex is formed at locations where the gas phase distribution in the impeller flow channel is concentrated. The outlet of the impeller is more prone to bubble consolidation under high gas content conditions. In conclusion, the MUSIG model can well predict the complex flow characteristics of gas–liquid two-phase inside the PAT and identify the key influencing factors of energy acquisition, which can provide support for improving the performance of the PAT design.

Long-term Outcomes of Deep Anterior Lamellar Keratoplasty in Macular Corneal Dystrophy—A Retrospective Analysis

Abstract Purpose: To study the long-term outcomes and complications in patients who underwent deep anterior lamellar keratoplasty (DALK) for macular corneal dystrophy (MCD). Methods: This is a retrospective analysis of all patients who underwent DALK in a tertiary eye care hospital in South India from 2011 to 2020. A total of 51 eyes of 33 patients were evaluated. All eyes underwent successful DALK by big bubble technique (32 eyes) or layer-by-layer dissection (19 eyes). Patients were followed up for 18 months to 9 years. Results: There was a significant improvement in vision (uncorrected and best-corrected visual acuity) post-DALK. The best corrected visual acuity after surgery was 0.3 logMAR (20/40) or better in 66.7% of operated eyes. Complications noted during surgery were intra-operative perforation. Post-operative complications include double AC, cataract, raised intraocular pressure, interface vessels and recurrence of the dystrophy. Conclusion: DALK is a safe and viable procedure for MCD management and gives good visual outcomes.

Bubby behavior and heat transfer characteristics of bionic microchannels in the subcooled flow boiling process

Microstructures on the sidewall or bottom wall, have shown excellent heat transfer performance in the single-phase convective heat transfer of microchannel heat sinks. For increasing the heat flux, phase-change heat transfer was highlighted as an effective approach. However, more complicated mechanisms of boiling heat transfer make less study focused on the microchannel with microstructure. In this work, a bionic microchannel with concave cavities and bionic ribs was proposed to enhance the boiling heat transfer. Numerical simulations, along with the volume of fluid (VOF) analysis combined with a phase-change model, were used to investigate the effect of the microstructure on the behavior of bubbles in the subcooled flow boiling. The results showed that the microstructure promotes bubble nucleation and the occurrence of more small bubbles around big bubbles. Thus, it enhances boiling heat transfer. Meanwhile, the microstructure was found to be beneficial in maintaining a stable liquid film evaporation under annular flow and suppressing boiling instability. Ultimately, compared with rectangular microchannels, the reported wall temperature and inlet pressure are more stable in the proposed bionic microchannel, the heat transfer coefficient and critical heat flux of the bionic microchannel were found to be 1.45 times higher, with mass flux G of 498 kg/(m2·s) and heat flux q w of 600 kW/m2.

Spike sign - To predict the formation of big bubble in deep anterior lamellar keratoplasty in advanced keratoconus.

Lamellar surgeries have revolutionized our understanding and practice of keratoplasties. However, the learning curve in deep anterior lamellar keratoplasty (DALK) makes it daunting for novice surgeons. This paper describes a unique intraoperative sign - the radial "spike sign," which heralds the commencement of a big bubble in some cases of advanced keratoconus in eyes that have not undergone any previous surgery. The spike sign was noted during big bubble DALK surgery and was then retrospectively looked for in recorded DALK surgical videos and correlated with the formation of a big bubble. The movement of air after injection was classified into the direct formation of a big bubble, stromal emphysema with no big bubble, and emphysema with the spike sign followed by a big bubble. In total, 104 surgical videos of big bubble attempts were evaluated and classified as such. The spike sign helps reduce the number of unnecessary attempts at big bubble formation during DALK, thus improving surgical outcomes.

Optimized Kalinnikov-Dinh technology for effective pre-Descemet's endothelial keratoplasty (PDEK) graft preparation and preservation.

We report an optimized Kalinnikov-Dinh technology for pre-Descemet's endothelial keratoplasty (PDEK) that involves the use of a ring fixator, base, 30G needle connected to a 5-ml syringe with a spring-loaded plunger, and storage media. Our method allows to minimize graft preparation failure and preserves the PDEK graft efficiently, by reducing complications associated with the formation of type 1 big bubbles, including bubble rupture, perforation of Descemet's membrane and endothelium, and formation of type 2 or mixed type of big bubbles, and may contribute to increasing the number of surgeons performing PDEK around the globe.

Identification and Management of a Central Type 2 Big Bubble in Deep Anterior Lamellar Keratoplasty

Purpose: The purpose of this study was to document a case of central type 2 bubble formation during deep anterior lamellar keratoplasty and discuss its intraoperative management. Methods: A rare case of central type 2 bubble formation with no peripheral extension beyond the trephination mark was documented with operative video and concurrent intraoperative optical coherence tomography imaging. Results: The type 2 bubble was decompressed with a needle intraoperatively, and deep anterior lamellar keratoplasty was successfully performed without perforation of Descemet membrane. Conclusions: Identifying formation of a type 2 bubble during deep anterior lamellar keratoplasty is crucial in avoiding perforation of Descemet membrane. This case shows that the behavior of type 2 bubbles can be different than what has been widely reported. It is hoped that this will aid the surgeon in identifying a type 2 bubble and in properly managing it intraoperatively.

Fluidization characteristics of wide-size-distribution particles in the fluidized bed with heating plate

To study the effect of heating plate on fluidization characteristics, the mean bed voidage, the axial solid concentration and pressure fluctuation under different superficial gas velocity were investigated. Experiments were conducted in a fluidized bed of 1500mm in height and 215 mm internal diameter with a conic bed. The results show that the internal heating fluidized bed has a little higher pressure drop, a little lower bed voidage, but a more stable fluidized state. The increase of the coalescence and breakage frequency of the bubbles can explain that the heating plate breaks the big bubbles well.

A multi-physics approach for modelling noise mitigation using an air-bubble curtain in impact pile driving

Underwater noise from offshore pile driving has raised significant concerns over its ecological impact on marine life. To protect the marine environment and maintain the sustainable development of wind energy, strict governmental regulations are imposed. Assessment and mitigation of underwater noise are usually required to ensure that sound levels stay within the noise thresholds. The air-bubble curtain system is one of the most widely applied noise mitigation techniques. This paper presents a multi-physics approach for modeling an air-bubble curtain system in application to offshore pile driving. The complete model consists of four modules: (i) a compressible flow model to account for the transport of compressed air from the offshore vessel to the perforated hose located in the seabed; (ii) a hydrodynamic model for capturing the characteristics of bubble clouds in varying development phases through depth; (iii) an acoustic model for predicting the sound insertion loss of the air-bubble curtain; and (iv) a vibroacoustic model for the prediction of underwater noise from pile driving which is coupled to the acoustic model in (iii) through a boundary integral formulation. The waterborne and soilborne noise transmission paths are examined separately, allowing us to explore the amount of energy channeled through the seabed and through the bubble curtain in the water column. A parametric study is performed to examine the optimal configuration of the double bubble curtain system for various soil conditions and pile configurations. Model predictions are compared with measured data. The model allows for a large number of simulations to examine different configurations of a single bubble curtain and a double big bubble curtain.

Measurement of bubble size and froth velocity using convolutional neural networks

Bubble size and froth velocity are the most important froth characteristics used for evaluating and controlling flotation systems. Bubble size is often measured using watershed and edge detection algorithms. These algorithms typically result in the over-segmentation of big bubbles or the under-segmentation of small ones. Froth velocity is usually determined by processing successive images using various techniques such as pixel tracing, block matching, and bubble tracking. Most of these algorithms perform well but are quite slow. Pre-trained convolutional neural networks are more accurate and simpler models for image classification and feature extraction. In this research, a new approach based on using a pre-trained convolutional neural network to measure bubble size and froth velocity from froth flotation images is proposed. The results demonstrate that pre-trained convolutional neural networks can serve as a more reliable and faster approach than classical image processing algorithms for analyzing froth images.

Cavitation evolution and flow field characteristics of transient flows with multi-point water-column separations in undulating pipeline

Transient flows with water-flow-induced multi-point cavitation inside an undulating pipeline are investigated experimentally under conditions of fast valve closure for three typical test cases by using high-precision pressure transducers, high-speed photography and particle image velocimetry (PIV) techniques. For low initial velocity condition, the transient pressure at the monitoring point (PT1) downstream the valve quickly decreases to the cavitation pressure and fluctuates near it. The leading-edge velocity of the dispersed bubble-like cavitation group first increases with its occurrence and then accelerates and reaches an extreme value before decreasing to zero due to the viscous force and the decrease of water flow inertia, and finally the water flows upstream in reverse, i.e. the leading-edge accelerates and collapses behind the valve. At the same time, the transient pressure rises sharply to maximum 81.86 m due to the return of the compression wave and then decreases sharply to cavitation again because of the switch of the pressure waves. Then, the second cavitation intensity is weak and the corresponding pattern is fog-like, and finally decreases gradually with a cyclic period of about 0.38 s. The transient pressure at the monitoring point (PT2) at the peak of the undulating pipeline also maintains at the cavitation pressure corresponding to the big bubble occurrence moment in addition to its fluctuation near the cavitation pressure including first and second cavitation. Its maximum pressure is 72.16 m and the corresponding cavitation pattern is small and bigger bubbles at different cavitation stages. For middle initial velocity, the typical pattern of the corresponding cavitation is the large cavity with free surface at PT2, the corresponding higher maximum pressures are 102.36 m at PT1 and 84.81 m at PT2. The evolution process of the cavity including bubble mergence, morphological deformation, motion and collapse is analysed based on the broken wave and hydraulic dynamic theories. For high initial velocity, larger cavities occur both downstream the valve and at the peak point of undulating pipeline, and thus the corresponding higher maximum pressures due to larger cavity collapse are 140.56 m at PT1 and 127.98 m at PT2. In particular, complete water column separation with transparent large cavity occur downstream the valve.

Characterizing bubble dynamics in combustion and atomization of alcohol/PODE4 and alcohol/n-undecane binary droplets

This work explores bubble dynamics in the combustion and atomization of binary droplets, with special attentions on the effects of bubble dynamics on the combustion and atomization characteristics. A typical renewable synthetic fuel polyoxymethylene dimethyl ether 4 (PODE4) and a typical kerosene component n-undecane are used as the weakly volatile components, while C1-C5n-alcohols are used as the highly volatile components in order to change the boiling point difference of components in the binary droplets. Nucleation capability of alcohol/PODE4 binary droplets is found to be higher than that of alcohol/n-undecane binary droplets. Alcohol/PODE4 binary droplets with higher boiling point differences (ΔTbp s) tend to have multiple nucleation sites and undergo multiple bubble growth and coalescence, while most of the rest binary droplets tend to have limited nucleation sites and undergo single bubble growth. The bubble evolution velocity decreases with the decreasing ΔTbp, while the bubble growth in alcohol/PODE4 binary droplets are generally slower. Bubble breakup mainly results in ejection and micro-explosion in this work, which are associated with small and big bubble breakup, respectively. Five atomization modes with different bubble evolution, bubble breakup and droplet atomization processes are concluded. The combustion and atomization characteristics of most of the investigated binary droplets are remarkably influenced by the bubble dynamics. The binary droplets with higher ΔTbp s are susceptible to strong atomization modes and consequently tend to have shorter normalized droplet lifetimes and larger atomization indices. Alcohol/PODE4 binary droplets have generally greater atomization indices than alcohol/n-undecane binary droplets.

Double-Docking Technique for Femtosecond Laser-Assisted Deep Anterior Lamellar Keratoplasty: A Retrospective Consecutive Case Series Study of Advanced Keratoconus.

The aim of this study was to report the clinical outcomes and prognosis of femtosecond laser (FSL)-assisted double-docking deep anterior lamellar keratoplasty (DD-DALK) for advanced keratoconus (AK). Records of consecutive patients with keratoconus who underwent FSL-assisted DALK (DD-DALK) were reviewed. We analyzed 37 eyes from 37 patients who underwent DD-DALK. Sixty-eight percent of eyes had a successful big-bubble formation and 27% had a manual dissection to achieve the DALK deep dissection. Stromal scarring was associated with not achieving a big bubble. Intraoperative conversion to penetrating keratoplasty was conducted in 2 cases (5%). The best-corrected visual acuity improved from a median (± interquartile range) of 1.55 ±0.25 logMAR preoperatively to 0.2 ±0.2 logMAR ( P < 0.0001). The median postoperative spherical equivalent was -5.75 ±2.75 D with a median astigmatism of -3.5 ±1.3 D. BCVA, SE, and astigmatism were not statistically different between patients who underwent DD-DALK and patients who underwent manual DALK. Stromal scarring was associated with big-bubble (BB) formation failure ( P = 0.003). All patients with failed BB requiring manual dissection had anterior stromal scarring. DD-DALK is safe and reproducible. The success rate of BB formation is hampered by stromal scarring.

Double bubble pneumo-descemetopexy for the management of Descemet membrane detachment: An innovative technique.

A 62-year-old woman was referred with poor vision following manual small incision cataract surgery. On presentation, the uncorrected distance visual acuity in the involved eye was 3/60, whereas slit-lamp examination revealed a central corneal edema with the peripheral cornea relatively clear. Direct focal examination with a narrow slit upper border and lower margin of detached rolled up Descemet's membrane (DM) could be visualized. We performed a novel surgical approach, "double-bubble pneumo-descemetopexy." The surgical procedure included unrolling of DM with "small air bubble" and descemetopexy with "big bubble." No postoperative complications were observed, and best corrected distance visual acuity improved to 6/9 at 6 weeks. The patient had a clear cornea and maintained BCVA 6/9 during 18 months at follow-up. Double-bubble pneumo-descemetopexy, a more controlled technique, provides a satisfactory anatomical and visual outcome in DMD without the need for endothelial keratoplasty (Descemet's stripping endothelial keratoplasty or DMEK) or penetrating keratoplasty.

Ex vivo demonstration of canine corneal pre-Descemet’s anatomy using pneumodissection as for the big bubble technique for deep anterior lamellar keratoplasty

The recent discovery and characterization of pre-Descemet’s layer (PDL; also termed the Dua’s layer or the Dua-Fine layer) has advanced the understanding of various posterior corneal pathologies and surgeries in human. This study aimed to characterize the ultrastructure of the posterior stroma and interfacial zone of Descemet’s membrane (DM) in canine eyes. Eighteen canine corneo-scleral discs were included. Intrastromal air injection resulted in the formation of type 1 big bubble (BB) in 73% (n = 11/15) of corneas, with a mean diameter of 11.0 ± 1.3 mm. No type 2 BB was created. Anterior segment optical coherence tomography, histology and transmission electron microscopy confirmed that the wall of BB was composed of DM, in contact with remaining stroma (canine PDL; cPDL). The cPDL was populated with keratocytes, of varying thickness of 16.2 ± 4.2 µm in close apposition to the DM, and composed of collagen bundles arranged in transverse, longitudinal and oblique directions. The interfacial zone, between DM and cPDL, showed fibril extension in all three directions, predominantly longitudinal. Irregular extensions of DM material into cPDL stroma were observed. No long-spaced collagen was detected. In conclusion, there exists a well-defined cleavage plane between the posterior stroma and cPDL, with similar but not identical characteristics as in humans, that is revealed by pneumodissection. This adds to our understanding of the anatomy of the posterior most canine cornea, which will have significant clinical impact on posterior corneal surgery and understanding of corneal pathology in dogs.