Ultrasonic atomization, particularly in the form of acoustic fountains, is widely used in various fields, but its underlying mechanisms remain incompletely understood, with ongoing debates between wave-driven and bubble-driven hypotheses. This study introduces classic cavitation nucleus theory into high-frequency ultrasonic atomization research, focusing on the “gas-nucleus–cavitation–atomization” chain to provide reproducible evidence for the bubble-driven hypothesis. Experimental setups with a 1.7 MHz ultrasonic transducer, capillary tubes, and high-speed cameras were used to manipulate gas nuclei in acoustic fountains through pre-embedding, injection, and pouring methods. Results demonstrate a strong spatiotemporal correlation between gas nuclei and atomization—localized atomization occurs precisely at gas nucleus locations, and increasing gas nuclei content enhances atomization intensity. Simulated vibration sources (broken capillary tips) reproduce atomization characteristics similar to natural ultrasonic fountain atomization, confirming the critical role of vibrating bubbles derived from gas nuclei. Additionally, surface protrusions of acoustic fountains act as micro-resonators, and acoustic focusing within these structures promotes gas nucleus growth into vibrating bubbles, triggering atomization. Inhibiting surface fluctuations suppresses atomization, further supporting the mechanism. This study clarifies the pivotal role of gas nuclei in ultrasonic fountain atomization, providing a theoretical basis for precise control and efficient application of ultrasonic atomization technology.
Daniil A. Korotych, Vyacheslav I. Grishchenko, Alexey N. Beskopylny
This paper presents an original positional pneumatic actuator for long-stroke coordinate mechanisms. The design integrates a rodless pneumatic cylinder, a jet control system, and an external braking device. It achieves a positioning accuracy of 200 microns, a discrete step of 2 mm, and an average speed of 0.15 m/s over a maximum stroke of 6 m. This solution offers a two-fold improvement in technical, economic, and operational performance compared to electromechanical drives. A mathematical model of the drive was developed using SimInTech software and validated with a custom-built experimental stand. The discrepancy between calculated and experimental data does not exceed 18%. The study established the dependence of positioning accuracy on the load and kinematic characteristics of the drive, which helps reduce design time for coordinate mechanisms. As a result of the research, a new scheme of a positional pneumatic actuator has been developed and experimentally confirmed, which allows for a two-fold improvement in technical and economic indicators compared to electromechanical analogs due to the original combination of a rodless cylinder, a jet control system, and an external braking device.
Materials of engineering and construction. Mechanics of materials, Production of electric energy or power. Powerplants. Central stations
Ian E. Floyd, Alejandro Sánchez, Stanford Gibson
et al.
Non-Newtonian mud and debris flows include a wide range of physical processes depending on the setting, concentration, and soil properties. Numerical modelers have developed a variety of non-Newtonian algorithms to simulate this range of physical processes. However, the assumptions and limitations in any given model or software package can be difficult to replicate. This diversity in the physical processes and algorithmic approach to non-Newtonian numerical modeling makes a modular computation library approach advantageous. A computational library consolidates the algorithms for each process. This work presents a flexible numerical library framework (DebrisLib) that has a diverse range of software implemented to simulate geophysical flows using steady flow, kinematic wave, diffusion wave, and shallow-water models with finite difference, finite element, and finite volume computational schemes. DebrisLib includes a variety of non-Newtonian closures that predict a range of geophysical flow conditions and modular code designed to operate with any Newtonian parent-code architecture. This paper presents the DebriLib algorithms and framework and laboratory validation simulation. The simulations demonstrate the utility of the algorithms and the value of the library architecture by calling it from different modeling frameworks developed by the US Army Corps of Engineers (USACE). We present results with the one-dimensional (1D) and two-dimensional (2D) Hydrologic Engineering Center River Analysis System (HEC-RAS) and the 2D Adaptive Hydraulics (AdH) numerical models, each calling the same library.
Abstract Evapotranspiration (ET) is a key process in the hydrological cycle that can help mitigate urban heat. ET depends on the surface cover, as the surface affects the partitioning of precipitation between runoff and evapotranspiration. In urban neighborhoods, this surface cover is highly heterogeneous. The resulting neighborhood‐scale ET can be observed with eddy‐covariance systems. However, these observations represent the signal from wind‐ and stability‐dependent footprints resulting in a continuously changing contribution of surface cover types to the observation. This continuous change prevents quantifying the contribution of the surface cover types to neighborhood ET and their hourly dynamics. Here, we disentangle this neighborhood‐scale ET at two sites in Berlin attributing the patch‐scale ET dynamics to the four major surface cover types in the footprint: impervious surfaces, low vegetation, high vegetation, and open water. From the bottom‐up, we reconstruct neighborhood ET based on patch‐scale observations and conceptual models. Alternatively, we start top‐down and attribute neighborhood ET to the surface cover types solving a system of equations for three eddy‐covariance systems. Although data requirements for the bottom‐up approach are met more frequently, both approaches indicate that vegetation is responsible for more ET than proportional to its surface fraction in the footprint related to the large evaporating surface compared to the ground surface. Evaporation from impervious surfaces cannot be neglected, although it is less than from vegetation due to limited water availability. The limited water availability causes impervious surfaces to cease evaporation hours after rainfall, while vegetation and open water sustain ET for extended periods.
Abstract Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability, however usually constrained by limited data availability, hydrogeological variation, and the complex coupled hydro-mechanical behaviour. This paper aims to determine the factors and mechanism of groundwater depressurisation and identify knowledge gaps and methodological limitations for improving groundwater impact assessment. Analysis of dewatering cases in Australian, Chinese, and US coalfields demonstrates that piezometric drawdown can further lead to surface hydrology degradation, while the hydraulic responses vary with longwall parameters and geological conditions. Statistical interpretation of 422 height of fracturing datasets indicates that the groundwater impact positively correlates to panel geometry and depth of cover, and more pronounced in panel interaction and top coal caving cases. In situ stress, rock competency, clay mineral infillings, fault, valley topography, and surface–subsurface water interaction are geological and hydrogeological factors influencing groundwater hydraulics and long-term recovery. The dewatering mechanism involves permeability enhancement and extensive flow through fracture networks, where interconnected fractures provide steep hydraulic gradients and smooth flow pathways draining the overlying water to goaf of lower heads. Future research should improve fracture network identification and interconnectivity quantification, accompanied by description of fluid flow dynamics in the high fracture frequency and large fracture aperture context. The paper recommends a research framework to address the knowledge gaps with continuous data collection and field-scale numerical modelling as key technical support. The paper consolidates the understanding of longwall mining impacting mine hydrology and provides viewpoints that facilitate an improved assessment of groundwater depressurisation.
La cuenca El Hato, ubicada en la cuenca del río Pensativo en Sacatepéquez, Guatemala, abarca 558 hectáreas, de las cuales el 68% es de vocación forestal y el 20% es urbano y agrícola. El crecimiento poblacional y la falta de planificación territorial están provocando un aumento en la escorrentía superficial, degradación del suelo y disminución de la captación de agua en las áreas críticas de recarga hídrica. Este fenómeno representa un desafío para la gestión sostenible del recurso hídrico en la región. El objetivo de esta investigación fue identificar las áreas críticas de recarga hídrica y proponer un plan de manejo para su conservación. Se realizó un balance hídrico de suelos y se complementó con información sobre uso de la tierra, pendientes y geología, mediante sistemas de información geográfica. Luego, se identificaron y clasificaron las áreas críticas y se desarrolló un plan de manejo basado en las características del suelo, pendiente e intensidad de uso de la tierra. Finalmente, se evaluó el impacto hidrológico mediante simulaciones de caudales para cuatro períodos de retorno. Los resultados muestran que, de las 472 hectáreas de recarga hídrica potencial, 301 son críticas. Se propone restaurar 113 hectáreas y aplicar prácticas de conservación de suelo y agua en 188 hectáreas adicionales. La ejecución de esta propuesta podría reducir la escorrentía superficial en un 16% y mejorar la captación de agua en las áreas de recarga hídrica.
Anastasios I. Stamou, Georgios Mitsopoulos, Athanasios Sfetsos
et al.
Water Infrastructure (WI), incorporating water supply, wastewater, and stormwater systems, is vulnerable to climate change impacts that can disrupt their functionality; thus, WI needs to be adapted to climate change. In 2021, the European Commission (EC) released the technical guidelines on “Climate-proofing Infrastructure” that include mitigation and adaptation strategies; these guidelines, and the relevant guides that followed, focus mainly on climate change aspects without examining sufficiently the engineering features of WI that are described mainly in the relevant hydro-environmental research; this research is vast and includes various terminologies and methods for all aspects of climate change adaptation. The adaptation procedure of WI to climate change is improved when this research is known to guidelines’ developers. In the present work, to facilitate this knowledge transfer, we typologize the hydro-environmental research via its classification into five categories that are based on the EC guidelines and then perform a literature review that we present as follows: firstly, we introduce and typologize the climate hazards for WI systems and identify the most common of them in the Mediterranean region that we classify into seven groups; then, we classify the hydro-environmental research into five categories based on the EC guidelines, present the main aspects for each of these categories, discuss the future research; and finally, we summarize the conclusions.
El artículo trata sobre la caracterización de los residuos sólidos urbanos del municipio de Santa Catarina Pínula, analizando para ésto muestras de origen domiciliar, institucional y comercial. En la fracción domiciliar se analizó una muestra de 169 viviendas durante 5 días consecutivos, obteniéndose una producción percápita (PPC) de 0.83 kg/persona-día, siendo su composición física mayormente orgánica, con un 57.82% correspondiente a restos de comida. Estos residuos presentaron un alto porcentaje de humedad, 71.19%, así mismo una densidad de 233.23 kg/m³. En lo referente a los residuos de origen institucional y comercial, se realizaron muestreos puntuales, encontrándose en ambos casos que el mayor porcentaje lo constituyen los restos de comida con un 43.38 y 39.65%, así mismo densidades de 70.89 y 174.68 kg/m³ respectivamente. Se encontró además que los residuos de origen institucional tienen una considerable cantidad de papel y cartón 33.24%, y los residuos comerciales a su vez, un alto contenido de productos plásticos 24.20%. La caracterización es útil para estimar la carga contaminante de los residuos, así como para la elaboración de modelos de gestión integral de residuos sólidos.
La subcuenca del río Villalobos constituye la parte alta de la cuenca del río María Linda, se encuentra asentada parte de la ciudad capital de la república de Guatemala, así como municipios periféricos, región que ha experimentado un aumento constante de la población y consecuentemente de sus áreas urbanas. El cauce principal de la subcuenca es el río Villalobos, afluente principal al lago de Amatitlán. La investigación consistió en cuantificar el efecto asociado a la urbanización, sobre el ciclo del agua, principalmente sobre los componentes de escurrimiento superficial. Para estimar el impacto en el escurrimiento superficial, se modeló el hidrograma para el evento más extremo suscitado, siendo la tormenta tropical Agatha, para las condiciones de urbanización de los años 1972 y 2012. Los efectos sobre el hidrograma se estimaron en el caudal máximo, escurrimiento superficial (total y medio), tiempo de concentración, coeficiente de escorrentía así como los niveles de flujo alcanzados y ascensos estimados en el lago de Amatitlán. El aumento en las áreas urbanas en los últimos 40 años (aproximadamente 22%), ha ocasionado incrementos significativos en los componentes del hidrograma, caudal pico y escurrimiento superficial principalmente, disminuyendo únicamente en el tiempo de concentración.
<p>Plant hydraulics gains increasing interest in plant ecophysiology and vegetation modeling. However, the hydraulic properties and profiles are often improperly represented, thus leading to biased results and simulations, e.g., the neglection of gravitational pressure drop results in overestimated water flux. We highlight the commonly seen ambiguities and/or misunderstandings in plant hydraulics, including (1) the distinction between water potential and pressure, (2) differences among hydraulic conductance and conductivity, (3) xylem vulnerability curve formulations, (4) model complexity, (5) stomatal-model representations, (6) bias from analytic estimations, (7) whole-plant vulnerability, and (8) neglected temperature dependencies. We recommend careful thinking before using or modifying existing definitions, methods, and models.</p>
George Meramveliotakis, Sotirios Karellas, George Kosmadakis
The aim of this work is to evaluate three methodologies regarding semi-empirical scroll compressor modeling for different refrigerants and conduct a comparative analysis of their results and accuracy. The first step is to improve a semi-empirical model for scroll compressors based on established techniques, and further enhance the physical background of some of its sub-processes leading to more accurate predictions. Focus is then given on the compressor operation when changing the refrigerant, proposing three methods in total. The first method refers to the standard model, requiring an optimization process for the calibration of all the model parameters. The second method relies on a reference refrigerant, and also uses optimization procedures, but for the fine-tuning of a small subset of the parameters. The third method is more generalized, without the need of any optimization process for the parameters identification, when fluid change occurs, leading to a very fast approach. Το evaluate the accuracy and verify the applicability of each method also related to the necessary computational time, two scroll compressors each with three different refrigerants are considered (HFCs and HFOs and their blends). The model is evaluated with the available manufacturer data, using R134a as reference refrigerant. The results show that the first method predicts the key indicators with a very high accuracy, with the maximum discrepancy of 2.06%, 4.17% and 3.18 K for the mass flow rate, electric power and discharge temperature respectively. The accuracy of the other two methods is dropping, but within acceptable levels in most of the cases. Therefore, in cases that reduced accuracy can be accepted, the third method is preferred for compressor performance prediction when changing the refrigerant, which provides results at a small fraction of time compared with the other two methods, once the parameters are calibrated for a reference case.
In this paper, five computational approaches are used to model bulk flow parameters of inclined round negatively buoyant jets. More specifically, an integral model employing Gaussian distributions for velocity and apparent acceleration of gravity, proposed in earlier study, is implemented with two different entrainment formulae. The remaining three computational approaches include an integral model known as EMA, which takes into consideration the fluid detachment occurring in the inner side of the flow near the terminal height, the widely known commercial model Corjet and analytical solutions that were proposed in a previous study. Predictions are provided for the maximum centerline height and its horizontal position, the terminal height of the upper jet boundary, the horizontal distance to the points where the jet centerline and the upper jet boundary return to the source level, the centerline dilution at the maximum height and the centerline dilution at the return point. Detailed comparisons are made in dimensionless form between the estimations provided by the models and a wide range of experimental data for discharge angles between 15° and 90°. Conclusions are drawn regarding the performance of the five computational approaches.
Thermodynamics, Descriptive and experimental mechanics
Viet Hoang Nguyen, Van Tuan Le, Thi Ha Nguyen
et al.
Ascertaining peak oxygen demand is crucial for plant designers to determine blower capacities of wastewater treatment plants in planning phase. To obtain this technical information without cumbersome influent sampling and analysis, a set of field-test activated sludge reactors equipped with DO and nitrate-N sensors was installed at 3 sites and continuously operated for a couple of months in each field. Under the controlled aeration and hydraulics of the reactors, the hourly influent oxygen demands were back-calculated as biodegradable constituents using the IWA-Activated Sludge Model #1. The daily maximum concentrations (rounded to last for 1-hour) of biodegradable organics and nitrogen were ranged between 45~258 mg-COD/L and 10.4~32.3 mg-N/L in Site #1; 119~244 mg-COD/L and 28.3~38.7 mg-N/L in Site #2; 194~552 mg-COD/L and 30.2~51.7 mg-N/L in Site #3 respectively. The marginal blower capacities to maintain at least 1.0 mg-O2/L of DO in the daily maximum oxygen demand were estimated based on the datasets using the statistical method, Extreme Value Distribution analysis. To maintain the DO concentration for 99 days out of 100 days of the plant operations, the blower capacity was supposed to be designed as high as 1.4~2.2 times than those of the blower calculated from the daily average concentration.
River, lake, and water-supply engineering (General), Environmental technology. Sanitary engineering
Nikolas T. Martzikos, Panayotis E. Prinos, Constantine D. Memos
et al.
Coastal storms as extreme hydrometeorological events have severe impacts on the coasts and consequently affect the coastal communities, attracting considerable research interest nowadays. Attempting to understand the risk of these extreme events, a coastal storm analysis is accomplished by studying the parameters which define a coastal storm and their properties, such as the wave height, the wave period, the duration, the calm period, and the storm energy. The frequency of occurrence of coastal storms, the thresholds of storm parameters and the way they are interrelating with each other draw a rough outline of wave climate during coastal storm events for a specific location. This information is valuable afterwards for the design of coastal structures and the coastal zone management. In this work, buoy datasets from 30 locations in the Mediterranean Sea are analysed for describing coastal storm activity. A sample of 4008 coastal storms is identified. Each location faces around 10–14 coastal storms per year, with most of them to occur in winter months and their characteristics to be site-dependent. Their average duration is lower than 30 hours, and 25% of them are consecutive events which hit the same location in less than a day. Furthermore, the wave period and the main direction present no remarkable fluctuations during a coastal storm. With this analysis, a deeper understanding of coastal storm severity is pursued, gaining knowledge about their past activity, in order to be prepared in the future and to protect the coastal areas.
Este artículo presenta una evaluación de vulnerabilidad y riesgo del acuífero subyacente en el municipio de San Pedro La Laguna, Sololá. La evaluación se realizó aplicando el método GOD (Groundwater occurrence-overall aquifer class-Depth) (Foster, 1987) para determinar la vulnerabilidad, y para determinar el riesgo y prioridad de protección, se combinaron los resultados de vulnerabilidad con el método de evaluación de carga contaminante POSH (Pollutant Origin Surcharge Hydraulically) (Foster e Hirata, 1988). Con la aplicación de la metodología en una pequeña región, se establecieron zonas de riesgo que fueron cotejadas con las concentraciones de nitratos detectados en las campañas analíticas que registraron concentraciones de nitratos en un rango de 7.92 a 118.80 mg/L en época lluviosa y 13.00 a 506.00 mg/L en época seca. Para una simple utilidad también se desarrollaron mapas de vulnerabilidad, riesgo y protección que pueden ser herramientas útiles para la planificación del ordenamiento territorial de la zona, el manejo y el control de los recursos hídricos.
An analytical approximation to the entire centerline trajectory of inclined round dense jets in dimensionless form is proposed, in terms of a fourth degree polynomial. The coefficients of the polynomial for a certain inclination angle can be easily obtained if the position of the maximum height and the return point are known. Experimental data of the authors are used to determine these coefficients for six inclination angles between 35° and 75°. The resulting trajectories are then compared to data of other investigators and found to be in good agreement. The variation of the polynomial coefficients with inclination angle is also studied. The proposed analytical expression allows for a straightforward computation of the trajectory length for any inclination angle in the range studied. It is found that the longest trajectory occurs for the 60° angle. The relation between the computed length and the measured minimum (centerline) dilutions at the location of maximum height and at the return point is examined. Finally, the laws governing the variation of the minimum dilution with the axial distance from the source are explored and similarities with the laws of simple jets and plumes are discussed.
Thermodynamics, Descriptive and experimental mechanics
Abstract An experimental Lead Lithium (PbLi) loop named DRAGON-V has been built at the Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences (INEST, CAS). The purpose of this loop is to test the technical issues of PbLi blankets for fusion reactors, such as thermal hydraulics, material corrosion, magnetohydrodynamics (MHD) effect and safety issues, etc. The main heat recovery system of the DRAGON-V loop is the Concentric Recuperator Heat Exchanger (CRHE) which was made of T91 steel. It has counter flow arrangements with PbLi as the working fluid across the tube and shell sides. In this paper, the system was analyzed in detail for thermal performance, pressure drop, pumping power, entropy generation, the effect of inlet temperature of shell side fluid on overall performance, and the temperature distribution and flow characteristics. It was found that the effectiveness and heat transfer rate of the CRHE was decreased with the inlet temperature of the PbLi across the shell side. The difference of effectiveness calculated by correlation and simulation was about 4.5%. The high pumping power of PbLi fluid circulation was required on the shell side due to its thermo-physical properties variation, which resulted in the high pressure drop across the shell side as compared to the tube side. The temperature variation across the tube and shell sides indicated that the simulation results agreed well with the design parameters within a deviation of less than ˜ 5%.
It is of significant value to understand the unsteady hydraulic features and pressure pulsation transmission path in the flow channel through a turbine for providing technical support for turbine design and optimization, as well as laying a foundation for analysis of the stability and the coupled vibration of the hydropower house. In this paper, a three-dimensional mechanics–hydraulics–concrete structure coupled numerical model was established to accurately simulate Francis hydraulic machinery, including the high-rotating turbine runner and fixed guide vane, the unsteady flowing water, the structure of the entire flow channel, as well as the dynamic interaction between them. Turbulent hydraulic features of flow condition and pressure pulsation in design operation were explored using the detached eddy simulation (DES) turbulence model. Then, a novel method was proposed to identify the fluid pressure pulsation transmission path based on the time-delayed transfer entropy method and wavelet theory. On basis of time and frequency analysis of pressure calculation results, investigation into identification of pressure pulsation transmission path was performed using the method of traditional transfer entropy and the method adopted in this paper. The pressure pulsation transmission features in the entire flow channel were revealed during operation of the large-scale Francis turbine. The research method and results could not only lay a basis for exploring the structural vibration regularity of the hydropower house but also provide a scientific reference for vibration reduction design of the hydropower house.