Search Results (53)

This study investigated the suppression effects and mechanisms of fine water mist on methane/air explosions through large-scale roadway experiments and numerical simulations. Experiments showed that fine water mist curtains deployed at 40 m and 70 m effectively mitigate flame propagation and reduce overpressure. A coupled gas–liquid numerical model was developed to reproduce flame dynamics and droplet–flow interactions. The simulations revealed droplet breakup, transport, and coupling with the evolving explosion flow field, providing mechanistic insight into gas–liquid interactions in a confined roadway. Suppression by fine water mist is primarily driven by heat absorption and cooling, while radical chain interruption plays a secondary role. These coupled mechanisms significantly reduce flame propagation velocity and pressure rise rate, achieving complete suppression under optimized configurations. This study provides a solid foundation for the design and optimization of water mist explosion suppression systems in large-scale roadways. Full article

For the Vacuum Induction Gas Atomization (VIGA) powder preparation process, a multi-scale coupled numerical simulation and experimental validation were employed to systematically reveal the influence mechanisms of process parameters on the primary atomization flow field structure, secondary atomization droplet breakup behavior, and powder particle size distribution Using Computational Fluid Dynamics (CFD) methods combined with the VOF (Volume of Fluid) multiphase flow model, the fragmentation morphology of the melt during primary atomization was simulated, capturing the dynamic characteristics of liquid film thinning and the reduction in initial droplet area. Concurrently, the DPM (Discrete Phase Model) coupled with the TAB (Taylor Analogy Breakup) model was applied to predict the droplet size distribution in secondary atomization. The results indicate that increasing atomization pressure (2.5–4.5 MPa) significantly enhances secondary fragmentation intensity, reducing the median particle size (D50) from 42.1 μm to 37.5 μm. Experimental studies on Ni-based superalloys, validated by laser particle size analysis, confirmed that higher atomization pressure improves gas velocity and gas–liquid energy conversion efficiency, optimizes turbulent flow structures, and refines powder particles. The study concludes that the multi-scale coupled model effectively predicts atomization dynamics. By optimizing atomization pressure, powder particle size can be significantly refined, providing a theoretical basis for process control of high-performance spherical powders used in additive manufacturing. Full article

Purpose: To evaluate the clinical efficacy and safety of eye drops containing lyophilized amniotic membrane (AM) in the treatment of dry eye disease (DED), with a focus on tear film stabilization and epithelial–immune balance. Methods: In this prospective cohort study, 40 patients (80 eyes) with DED were followed over six visits. The primary outcome was tear break-up time (TBUT). Secondary outcomes included corneal and conjunctival staining graded by the Oxford scale, meibomian gland parameters, corneal sensitivity (Cochet–Bonnet esthesiometry), best-corrected visual acuity, intraocular pressure (IOP), and Schirmer I test. Continuous variables were analyzed using repeated-measures ANOVA with Greenhouse–Geisser correction and Bonferroni post hoc testing; ordinal outcomes were analyzed using the Friedman test with Dunn–Bonferroni correction. Results: TBUT increased significantly in both eyes (OD: +5.3 s; OS: +4.9 s; both p < 0.001; ηp² ≈ 0.33). Corneal and conjunctival staining scores decreased (p < 0.001), meibomian gland quality and expressibility improved (p < 0.001), and corneal sensitivity increased (p < 0.001), while visual acuity and IOP remained stable. Schirmer I values showed no significant change. The combined pattern of changes (TBUT ↑, staining ↓, meibum/expressibility ↑, sensitivity ↑) indicates tear film stabilization and ocular surface improvement with a preserved safety profile. Conclusions: Lyophilized AM eye drops significantly prolong TBUT and improve clinical signs of DED, presumably by restoring the extracellular matrix (ECM) niche and the heavy-chain hyaluronan/pentraxin 3 (HC-HA/PTX3) complex, reducing proteolytic burden, and promoting a pro-resolving immune balance, with potential neurotrophic effects. These findings support the adjunctive use of AM-derived eye drops within contemporary TFOS DEWS II-based management algorithms for dry eye disease. Full article

Liquid rocket engine injectors play a fundamental role in determining combustion efficiency, stability, and overall propulsion performance. This review paper provides a comprehensive analysis of liquid-injector technologies used in space propulsion systems, with emphasis on their historical evolution, atomization mechanisms, and cross-domain insights from aviation fuel injection systems. The study begins by examining the fundamental processes governing liquid jet breakup, including primary and secondary atomization, ligament formation, and droplet generation, together with the non-dimensional parameters that control these phenomena. The historical development of injector architectures -from early orifice-based and impinging designs to modern coaxial and pintle configurations—is then discussed in relation to increasing performance requirements and combustion stability challenges. A comparative perspective with aviation gas turbine injectors is introduced to highlight similarities in atomization physics and differences in operating conditions and design constraints. The paper also reviews experimental and numerical approaches used to characterize spray formation and injector performance. The results indicate that injector geometry and flow conditions strongly influence mixing efficiency, droplet size distribution, and combustion–acoustic coupling mechanisms. The study concludes that integrating cross-domain knowledge and modern design techniques is essential for advancing injector performance in next-generation propulsion systems. Full article

Space constraints in shipboard carbon capture require compact absorbers with high gas–liquid mass-transfer efficiency. However, the performance of emerging packing geometries cannot be inferred reliably from bed-scale correlations alone because liquid distribution and interfacial transport depend on unit-cell flow organization. This study aims to compare the micro-scale hydrodynamics and CO₂ mass-transfer behavior of the Kelvin cell and a Mellapak 250Y corrugated sheet unit using three-dimensional CFD simulations over liquid loads of 10 to 100 m³/(m²·h). The corrugated sheet guides liquid mainly along corrugation crimps, whereas the Kelvin cell redistributes liquid through its strut network and node intersections. For the M250Y unit, the periodic dripping cycle shortens as liquid load increases, and liquid holdup reaches only about 8% at 100 m³/(m²·h). In contrast, the Kelvin cell evolves from discrete dripping to liquid bridging and secondary breakup, maintains a liquid holdup about 3 to 6 times that of the corrugated sheet and delivers 2 to 3 percentage points higher mass-transfer efficiency. These results suggest a local hydrodynamic and mass-transfer advantage of the Kelvin cell over the M250Y benchmark under the present REU-scale conditions. Full article

Liquid entrainment presents a significant challenge in wet flue gas desulfurization systems, leading to downstream corrosion and secondary pollution. This study systematically investigates the characteristics of liquid entrainment and pressure drop in a gas cyclone–liquid jet absorption separator (GLAS) through both experimental and simulation methods. The effects of inlet gas flow rate (Q_G), absorbent flow rate (Q_L), overflow pipe insertion depth, and the presence of a liquid-guiding cover (LGC) were evaluated. The results revealed that liquid entrainment initially increased and then decreased with rising Q_G, Q_L, and insertion depth of overflow pipe, given the competing effects of turbulent jet breakup and centrifugal separation. To mitigate liquid entrainment, a novel LGC was introduced at the overflow pipe outlet. This intervention resulted in a reduction in liquid entrainment by up to 23.9%, achieved through physical interception and inertial impaction, while maintaining the difference value of pressure drop of less than 302 Pa. The numerical simulations further analyzed the gas–liquid two-phase distributions in GLAS under various operating conditions, with results that align well with experimental observations. These findings offer valuable insights for mitigating liquid entrainment in GLAS and optimizing its industrial applications. Full article

Background and Objectives: This study evaluates the safety, tolerability, and efficacy of preservative-free Dorzolamide 2%-Timolol 0.5% (PF-DT), with a focus on improving the ocular microenvironment in a real-world transition setting. Materials and Methods: A prospective, multicenter, open-label study involving thirty patients with dry eye disease previously treated with BAK-DT was conducted. Participants were transitioned to PF-DT, and evaluated at weeks 4, 12, and 24. The primary endpoint was the Ocular Surface Disease Index (OSDI) score. Secondary outcomes included Break-Up Time (BUT), Schirmer test results, corneal staining, conjunctival hyperemia, intraocular pressure (IOP), and patient satisfaction. Results: Twenty-five patients completed the study. The OSDI improved from 21.5 to 12.5 (p < 0.001), with 60.0% of patients showing improvement and 52.0% achieving complete symptom resolution. Among eyes with corneal staining, 78.4% demonstrated a reduction of at least one grade, and 50.0% of those with conjunctival redness showed similar improvement. By week 24, 78.0% exhibited no corneal staining, and 50.0% had no conjunctival redness. BUT increased from 5.0 to 7.0 (p < 0.01), while IOP decreased by 1 mmHg (p < 0.01). Satisfaction regarding comfort (≥80%) and handling (≥50%) was high, with 88.0% preferring PF-DT. Conclusions: Transitioning to PF-DT improved ocular surface health while maintaining IOP control, supporting the benefits of preservative-free formulations in restoring microenvironment homeostasis and enhancing tolerability and patient satisfaction. Full article

The breakup process of molten metal is the most critical stage in atomization powder production. Conducting systematic research on the breakup process of molten metal during gas atomization is highly significant for understanding the formation mechanism of droplets. In this study, a mathematical model suitable for investigating the breakup mechanism of molten aluminum in high-speed gas atomization was developed by coupling large eddy simulation (LES) with the volume of fluid (VOF) model, incorporating adaptive mesh refinement technology and periodic boundary conditions. Furthermore, the breakup behavior of molten aluminum in two close-coupled atomizers with distinct delivery tube end geometric (non-expanded type and expanded type, abbreviated as ET atomizer and NET atomizer) were compared. The development of surface waves, as well as the formation mechanisms of liquid cores, liquid ligaments, and liquid droplets during gas atomization, were systematically analyzed. The results indicated that Kelvin–Helmholtz instability was the predominant factor contributing to the primary breakup of molten metals. For the NET atomizer, the recirculation zone predominantly governed the primary breakup of molten metal, whereas the nitrogen main jet primarily controlled the secondary breakup. In the case of ET atomizer, under the influence of atomizing gas, a “conical” liquid core gradually formed, and numerous primary liquid droplets separated from the liquid core before undergoing secondary breakup. Compared to the ET atomizer, the NET atomizer produced droplets with a smaller average size. Full article

The study of the dynamics during droplet breakup is fascinating to engineers. Some industrial applications include fire extinguishing by sprinkler systems, painting of various components, washing processes, and fuel spraying in internal combustion engines, which involve the interaction between liquid droplets, gaseous flow field, and walls. In this work, washing operations effectiveness of civil aviation aircraft engines is analyzed. Periodic washing operations are necessary to slow down the effects of particle deposition, e.g., gas turbine fouling, to reduce the specific fuel consumption and the environmental impact of the gas turbine operation. This analysis describes the dynamics in the primary breakup, related to the breakup of droplets due to aerodynamic forces, which occur when the droplets are set in motion in a fluid domain. The secondary breakup is also considered, which more generally refers to the impact of droplets on surfaces. The latter is studied with particular attention to dry surfaces, investigating the limits for different breakup regimes and how these limits change when the impact occurs with surfaces characterized by different wettability. Surfaces with different roughness are also compared. All the tested cases are referred to surfaces at ambient temperature. Dimensionless numbers generalize the analysis to describe the droplet behavior. The analysis is based on several data reported in the open literature, demonstrating how different washing operations involve different droplet breakup regimes, generating a non-trivial data interpretation. Impact dynamics, droplet characteristics, and erosion issues are analyzed, showing differences and similarities between the literature data proposed in the last twenty years. Washing operation and the effects of gas turbine fouling on the aero-engine performance are still under investigation, demonstrating how experiments and numerical simulations are needed to tackle this detrimental issue. Full article

When detected early, canthoplasty controls the clinical signs and complications associated with accentuated eye exposure. The aim of this study was to evaluate the reduction in the palpebral fissure to prevent ophthalmic lesions secondary to brachycephalic dog syndrome. A total of 64 eyes of brachycephalic dogs were studied, divided into the control group (22 eyes submitted to traditional clinical treatment) and the treated group (42 eyes submitted to canthoplasty). Tear production, tear film break-up time (TFBUT), tear crystallization time (TCT), and the occurrence of corneal ulcers were assessed prior to treatment (T0), seven days after therapy or surgery (T7), and after 30 days (T30), and reassessments were performed every three months, until month 18. It was observed that the treated animals (treated group) showed an improvement in tear production compared to the control animals (control group). In addition, the treated animals showed a significant increase in TFBUT (T9M), which was higher than the control group. The TCT evaluation scores of the treated group decreased compared to the control group (T12M), and the occurrence of corneal ulcers was significantly higher in the control group in the medium term. We concluded that early canthoplasty in brachycephalic dogs prevented the occurrence of secondary lesions, increased tear production and quality, and reduced the occurrence of ulcers, particularly in the medium term. Full article

Megacrystalline uraninite within Neoproterozoic migmatites in the Haita area of the Kangdian region of China provides a unique condition for the investigation of uraninite typomorphism under high-temperature conditions. The present study represents the first systematic characterization of the typomorphic signatures and genetic significance of megacrystalline uraninite via optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XRS), and electron probe microanalysis (EPMA). The results show that uranium mineralization occurs as euhedral megacrystalline uraninite (black grains ≤ 10 mm) hosted in quartz veins, exhibiting frequent rhombic dodecahedral and subordinate cubic–octahedral morphologies. The paragenetic assemblage is quartz–uraninite–titanite–apatite–molybdenite. The investigated uraninite is characterized by elevated unit-cell parameters and a reduced oxygen index, with complex chemical compositions enriched in ThO₂ and Y₂O₃. These typomorphic characteristics indicate crystallization under high-temperature reducing conditions with gradual cooling. Post-crystallization tectonic fragmentation and uplift-facilitated oxidation occur, generating secondary uranium minerals with concentric color zonation (orange–red to yellow–green halos). Mineralization was jointly controlled by migmatization and late-stage tectonism, with the breakup of the Rodinia supercontinent serving as the key driver of fluid mobilization and ore deposition. The data materialized in the present study improve our knowledge about uranium mineralization during continental breakup events. Full article

The spray evaporation process in the boiler desuperheater involves complex droplet behaviors and fluid–thermal coupling, and its temperature distribution characteristics greatly affect the performance and safety of industrial processes. To better understand the process characteristics and develop the optimal desuperheater design, computational fluid dynamics (CFDs) was applied to numerically investigate the flow and thermal characteristics. The Eulerian–Lagrangian approach was used to describe the two-phase flow characteristics. Both primary and secondary droplet breakup, the coupling effect of gas–liquid and stochastic collision and coalescence of droplets were considered in the model. The plain-orifice atomizer model was applied to simulate the atomization process. The numerical model was validated with the plant data. The spray tube structure was found to greatly affect the flow pattern, resulting in the uneven velocity distribution, significant temperature difference, and local reverse flow downstream of the orifices. The velocity and temperature distributions tend to be more uniform due to the complete evaporation and turbulent mixing. Smaller orifices are beneficial for generating smaller-sized droplets, thereby promoting the mass and heat transfer between the steam and droplets. Under the same operating conditions, the desuperheating range of cases with 21, 15, and 9 orifices is 33.7 K, 32.0 K, and 29.8 K, respectively, indicating that the desuperheater with more orifices (i.e., with smaller orifices) shows better desuperheating ability. Additionally, a venturi-type desuperheater was numerically studied and compared with the straight liner case. By contrast, discernible differences in velocity and temperature distribution characteristics can be observed in the venturi case. The desuperheating range of the venturi and straight liner cases is 38.1 K and 35.4 K, respectively. The velocity acceleration through the venturi throat facilitates the droplet breakup and improves mixing, thereby achieving better desuperheating ability and temperature uniformity. Based on the investigation of the spray evaporation process, the complex droplet behaviors and fluid–thermal coupling characteristics in an industrial boiler desuperheater under high temperature and high pressure can be better understood, and effective guidance for the process and design optimizations can be provided. Full article

This study investigates the atomization process in Respimat^® Soft Mist^TM Inhalers (SMIs) using a validated Volume of Fluid (VOF)-to-Discrete Phase Model (DPM) to simulate the transition from colliding liquid jets to aerosolized droplets. Key parameters, including colliding jet inlet velocity, surface tension, and liquid viscosity, were systematically varied to analyze their impact on the atomization, i.e., aerosolized droplet size distributions. The VOF-to-DPM simulation results indicate that higher jet inlet velocities enhance ligament fragmentation, producing finer and more uniform droplets while reducing total atomized droplet mass. The relationship between surface tension and atomization performance in colliding jet atomization is not monotonic. Reducing surface tension plays a complex dual role in the atomization process. On the one hand, lower surface tension enhances the likelihood of liquid jet breakup into a liquid sheet, leading to the formation of smaller ligaments under the same airflow conditions and shear forces. This increases the probability of generating more secondary droplets. On the other hand, reduced surface tension also destabilizes the liquid surface shape, decreasing the formation of fine, high-sphericity droplets in regimes where surface tension is a dominant force. Viscosity also influences atomization through complex mechanisms, i.e., lower viscosity reduces resistance to ligament breakup but promotes droplet interactions and coalescence, while higher viscosity suppresses ligament fragmentation, generating larger droplets and reducing atomization efficiency. The validated VOF-to-DPM framework provides critical insights for enhancing the performance and efficiency of inhalation therapies. Future work will incorporate nozzle geometry, jet impingement angles, and surfactant effects to better understand and optimize the atomization process in SMIs, focusing on achieving preferred droplet size distributions and emitted doses for enhanced drug delivery efficiency in human respiratory systems. Full article

The objectives of the study were to compare the efficacy and safety using ocular surface assessment between preserved and preservative-free brimonidine/timolol fixed-combination eye drops in glaucoma or ocular hypertension patients. Methods: This study was designed as a prospective, multicenter (three institutions), investigator-masked, parallel-grouped randomized clinical trial. The primary outcomes were corneal and conjunctival staining score, ocular surface disease index (OSDI) score, drug tolerance, and adherence rates at 12-week visits. The secondary outcomes were corneal and conjunctival staining score, OSDI score at 4-week visits and intraocular pressure (IOP), tear-film break-up time (TBUT), and bulbar/limbal hyperemia score at the 4- and 12-week visits. For safety assessment, best-corrected visual acuity (BCVA), systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and physical examination at 4 and 12 weeks and adverse events during the whole study period were analyzed. Results: Overall, 59 patients were enrolled and randomized into each group (29 preserved and 30 preservative-free). At the endpoint, 5 patients in the preserved group and 2 patients in the preservative-free group dropped out, leaving 24 and 28 patients in the preserved and preservative-free groups, respectively. Baseline characteristics showed no significant difference between the groups including age and sex. At the 12-week visit, intra-group change of OSDI scores did not change significantly compared to the baseline scores in both preserved and preservative-free groups (p = 0.791, 0.478, respectively). On the contrary, the corneal staining score and the conjunctival staining score showed a significant increase compared to the baseline score in the preserved group (p = 0.015, 0.009, respectively). Regarding drug satisfaction, higher proportions of patients in the preservative-free group reported convenience of installation (p = 0.002). Also, stinging and burning sensations in drug tolerance showed better results in the preservative-free group with a significant difference (p = 0.011). Safety assessment regarding systemic side effects such as SBP, DBP, and HR showed similar results between the preserved and preservative-free groups (p = 0.711, 0.232, 0.666, respectively). Conclusions: Preservative-free brimonidine/timolol showed comparable efficacy and safety, better corneal and conjunctival staining score with convenience of installation, and lower stinging and burning sensation. It is expected to be a proper treatment option for patients with glaucoma or ocular hypertension. Full article

The present study explored the relationship between airborne transmission and the saliva fluid properties of a human sneeze. Specifically, we aimed to understand if altering the saliva and its relationship to droplet breakup and stability can affect its transmission characteristics. The study aimed to answer this question using computational fluid dynamics, specifically, a hybrid Eulerian–Lagrangian model with a Spalart–Allmaras, detached eddy simulation turbulence model. The effort focused on a scenario with a sneeze event within a ventilated room. The study found that for sneezes, secondary breakdown processes are important. Thicker saliva that increased the Ohnesorge number displayed a clear resistance to aerosolization due to stabilized secondary breakup, leading the bulk of the drops having high settling rates that are less likely to drive airborne transmission. For instance, the use of xanthum gum, which increased the saliva viscosity by 2000%, reduced the formation of aerosols. Additionally, another class of modifiers that reduce saliva content was studied, which was also effective in reducing airborne transmission drivers. Zingiber, which reduced the saliva content, reduced the formation of aerosols. However, when considering the overall reduction in droplet volume, saliva modifiers such as cornstarch, xanthum gum, and lozenges increased the mean droplet size by 50%, 25%, and 50%, respectively, while reducing the overall droplet volume by 71.6%, 71.2%, and 77.2%, respectively. Conversely, Zingiber reduced the mean droplet size by 50% but increased the overall droplet volume by 165.7%. Overall, for this type of respiratory event, this study provides insight into the potential for modifying saliva characteristics that may impact airborne transmission and could introduce new tools for reducing airborne pathogen transmission. Full article