Search Results (405)

Airblast sprayers remain the dominant pesticide delivery system in California citrus; however, mechanistic characterization of spray transport and off-target fate under realistic field-scale atmospheric variability remains limited. Regulatory airblast drift assessments in the United States (U.S.) currently rely on a sparse, dormant-apple canopy representation, despite substantial structural differences from foliated citrus canopies that may influence drift behavior. To address this gap, this study quantified airblast spray drift in a commercial citrus orchard across multiple downwind distances under varied daytime meteorological conditions and evaluated the influence of distance and weather variables on measured drift. Airborne and sedimentation drift were measured from a conventional axial-fan airblast sprayer operating at 10.3 bar, 5.1 km·h⁻¹, and 935 L·ha⁻¹ in a 4.0 m tall mandarin (Citrus reticulata) orchard using a U.S. Environmental Protection Agency (EPA)-approved, International Organization for Standardization (ISO) standard 22866-aligned protocol. Drift collectors (n = 2688), including flat cards, artificial foliage, and horizontal and vertical string samplers, were deployed from 33 m upwind to 183 m downwind of the orchard edge. Airborne drift measurements showed no significant vertical stratification or near-field decay between 8 m and 23 m downwind (p > 0.05), indicating rapid plume homogenization following canopy exit. In contrast, sedimentation drift declined sharply within 30 m and attenuated logarithmically with distance, governed by progressive droplet depletion and plume dilution. Estimated drift cessation distances were 127.5 m for artificial foliage and 182.1 m for horizontal string samplers. Drift magnitude varied significantly among trials (p < 0.05), reflecting sensitivity to meteorological variability. Multiple linear regression identified wind direction, wind speed, and atmospheric pressure as significant predictors of downwind deposition (p < 0.05), whereas air temperature and relative humidity primarily influenced drift through evaporative control of droplet lifetime. Collectively, these results demonstrate that spray drift from foliated citrus canopies is substantially attenuated relative to dormant-canopy scenarios. Although not intended to define regulatory buffer distances, the high-resolution dataset generated provides mechanistically interpretable parameterization inputs for next-generation airblast drift models, supporting improved representation of canopy interactions, plume evolution, and meteorological modulation in regulatory exposure assessments. Full article

Upper Northern Thailand continues to face a protracted structural crisis from fine-particulate matter (PM_2.5), primarily driven by biomass burning and wildfires. Conventional mechanical capture systems, such as cyclones, often suffer a drastic efficiency drop when treating sub-micron particles. This study introduces an innovative Evaporative Condensation Growth Scrubber (ECGS) designed to bridge this technological gap by promoting the growth of fine particles through heterogeneous nucleation. Experimental testing across 10 different nozzle configurations was conducted to optimize the system’s performance. The results revealed that the ECGS system significantly outperformed the dry cyclone (Baseline) across all nine testing configurations. While the Baseline showed inherent limitations in capturing sub-micron particles, the ECGS demonstrated relative efficiency improvements ranging from 39.53% to 83.23% for PM_2.5, and 26.10% to 61.50% for PM₁₀ compared to the baseline. Optimal performance was achieved using a 90-degree injection angle and a 10 cm distance, which created a complete spray curtain and maximized collision probability. Under these conditions, the outlet PM_2.5 concentration stabilized at 11.81 µg/m³ within 180 s of water injection. Crucially, despite sensor interference caused by high relative humidity, the system’s effectiveness was confirmed by a significant difference in performance in PM₁₀ and PM_2.5 removal. The PM₁₀ collection efficiency outperformed that of PM_2.5 by 28.82%, providing empirical evidence that PM_2.5 particles successfully acted as nuclei for condensation and grew into the larger PM₁₀ size range. This particle growth enabled more effective centrifugal separation, demonstrating that the ECGS system offers a viable and efficient solution for fine particle removal in highly polluted environments. Full article

Fossil fuel depletion has increased interest in renewable alternatives such as biodiesel derived from non-edible plant oils. Droplet evaporation is a key process influencing fuel–air mixing and combustion efficiency in diesel engines. In this study, the evaporation characteristics of diesel and two non-edible biofuels, Jatropha and Castor, are investigated using computational fluid dynamics (CFD) under high-temperature and high-pressure conditions representative of engine environments. The numerical model incorporates the conservation equations of mass, momentum, and energy, together with the k–$\epsilon$ turbulence model and a discrete phase model to simulate droplet heating, motion, and mass transfer during evaporation. A comparative CFD analysis is performed to examine how fuel properties, ambient temperature, and droplet size affect the evaporation behaviour of diesel, Jatropha, and Castor droplets under identical engine-like conditions. The evolution of droplet diameter, temperature, velocity, and lifetime is analysed, and the applicability of the classical $D^2$-law is evaluated under different operating conditions. The results indicate that biofuel droplets generally evaporate faster than diesel droplets at lower temperatures, while evaporation trends become similar at higher temperatures. These findings provide insight into the evaporation behaviour of Jatropha and Castor fuels and their potential application in diesel engines. Full article

Spray drift is one of the most significant challenges in the application of Plant Protection Products (PPPs), as it contributes to water, soil, and food contamination and is highly associated with health risks to agricultural workers, bystanders, and rural residents. Spray drift is defined as the fraction of PPP that is carried away from the target area by air currents during application. Factors such as high wind speeds, low relative humidity, and elevated temperatures increase the risk of drift by promoting droplet evaporation and off-target movement. Technological advancements in spraying equipment, such as low-drift and air induction nozzles, have been shown to significantly reduce drift potential. Air induction nozzles mix air with the spray liquid, creating larger droplets that are less susceptible to drift. The primary objective of this study was to quantify the spray drift reduction achieved using cost-effective and easily applicable drift mitigation techniques that do not require specialized and expensive equipment compared to conventional application methods in vineyards under Southern European conditions. Field measurements followed the ISO 22866:2005 protocol, using a conventional axial fan air-assisted sprayer that is commonly used by vineyard farmers in Greece. This study was conducted on Savatiano vines, the most widely cultivated winemaking variety in the Attica region, characterized by its low height. The spraying techniques evaluated as spray drift mitigation measures were one-sided spraying applications of the outer vineyard row; one-sided spraying applications of the two last rows; spraying with closed air assistance on the outer rows; and finally, spraying with the use of air induction nozzles. Results indicated that each technique produced varying amounts of sedimenting drift over distance. Spraying without air assistance consistently generated the lowest levels of drift at almost all distances. While air induction nozzles initially increased drift deposition within the first 4 m, they significantly reduced drift beyond 5 m. These findings demonstrate that simple operational adjustments to conventional vineyard sprayers, particularly reducing or switching off air assistance in outer rows, can substantially decrease spray drift without requiring additional investment in specialized equipment. Overall, spraying without air support achieved the greatest drift reduction across all distances from the vineyard, followed by air induction nozzles, which were equally effective at further distances (past 5 m) but less so near the application area. The results provide practical guidance for vineyard growers seeking low-cost strategies to minimize agricultural input losses, environmental contamination, and improve the sustainability of pesticide applications. Full article

We developed an arbitrary Lagrangian–Eulerian (ALE)-based multiphysics model for evaporation from a contact-line-pinned sessile drop of neat water subject to a vertically oriented sinusoidal alternating current (AC) electric field applied across parallel-plate electrodes. The framework fully couples electrostatics, incompressible flow, heat transfer with evaporative cooling, and transient vapour transport in air, and includes an instantaneous, voltage-controlled electrowetting contact-angle response under constant-contact-radius conditions. Validation against published data shows that the model captures both pinned-droplet evaporation and electrically induced deformation. Because Maxwell traction scales with the squared electric-field magnitude, droplet height and contact angle exhibit a robust 2:1 frequency-doubled response, producing two peak–trough events per voltage period. The resulting periodic deformation drives oscillatory interfacial shear and internal recirculation, yielding a synchronous double-peaked evaporative-flux waveform. Gas-side analysis quantifies a time-varying diffusion-layer thickness via a characteristic diffusion length; two thinning events per period coincide with flux maxima, indicating that AC enhancement is dominated by periodic compression of the vapour boundary layer and reduced gas-side mass-transfer resistance. Increasing voltage amplitude (0–60 kV) strongly accelerates volume loss, while frequency has a secondary effect: the cycle-averaged flux rises from 1 to 10 Hz but decreases slightly at 20 Hz due to phase lag and weaker boundary-layer modulation. Full article

Olive pomace biochar, obtained through the pyrolysis of lignocellulosic biomass, has emerged as a sustainable and multifunctional additive for polymer composites. Its physicochemical properties, including porosity, surface area, and electrical conductivity, can be tailored by controlling feedstock type and pyrolysis conditions. Although mechanical reinforcement and thermal stability improvements are well documented, the influence of biochar on surface-related properties such as wettability and contact angle remains insufficiently explored for environmentally relevant composite systems. In this study, epoxy-based composites containing biochar synthesized at 750 °C were evaluated in terms of their water interaction behavior by monitoring the evaporation dynamics of ultra-pure water droplets (10 μL, 0.055 mS/cm conductivity) at eight time intervals between 20 and 580 s using high-resolution digital microscopy. Image enhancement and segmentation were performed prior to Discrete Cosine Transform (DCT) analysis to describe droplet geometry in the frequency domain. Time-dependent variations in the standard deviations of DCT coefficients were optimized using the Bat Algorithm, resulting in mathematical models capable of accurately representing droplet evolution and surface–fluid interactions. The primary novelty of this study lies in the development of a hybrid experimental–computational framework that integrates droplet-based wettability measurements with signal-domain analysis and metaheuristic optimization. Unlike conventional studies focusing solely on material characterization, this approach establishes quantitative relationships between surface behavior and numerical descriptors derived from DCT and the Bat Algorithm. The proposed methodology provides a data-driven tool for predicting wettability trends in biochar-reinforced composites and supports the development of moisture-resistant materials for coatings, packaging, and thermal insulation applications within the context of sustainable composite design. Full article

This study investigates the fuel discrimination capability of the flame volume mixing method (FV mixing method) in predicting the lean blowout (LBO) limits of different fuels. Conventional FV-based models exhibit limited sensitivity to variations in fuel properties, especially under lean conditions and for sustainable aviation fuels. In this work, an improved FV mixing method is proposed by replacing the classical droplet evaporation treatment with the Abramzon–Sirignano droplet evaporation model, which accounts for fuel-dependent liquid properties, Stefan flow, and coupled convective heat and mass transfer between the gas phase and droplets. As a result, the proposed method shows enhanced sensitivity to fuel variability and improves the prediction accuracy of the LBO limit for the sustainable aviation fuel Cat-C1. The model performance is validated through numerical simulations and compared with experimental data. The results indicate that, compared with the baseline FV mixing method, the proposed approach reduces the LBO prediction error by 5.7%. The improved FV mixing method provides a more robust framework for LBO prediction, with potential applications in fuel characterization and combustion optimization. Full article

Rising ambient temperatures pose significant challenges to the thermodynamic performance of trans-critical CO₂ refrigeration systems, as they reduce system efficiency and cooling capacity. To mitigate these adverse effects, a spray-cooling technique was employed to enhance the heat rejection process. A mathematical model of the spray-cooled gas cooler, employing a homogeneous-mixture assumption that treats air and water droplets as a single phase without velocity slip or temperature difference, was developed and validated against experimental data. The developed model was subsequently integrated into the refrigeration system model to evaluate the system’s performance with an air temperature range of 30 °C to 40 °C. The results show that spray cooling effectively decreases the CO₂ pressure and temperature exiting the gas cooler, lowers the compressor power consumption, enhances the evaporator cooling capacity, and significantly improves the overall system performance. The results also indicate that increasing the spray-water-to-air-mass flow rate ratio beyond around 0.075 yields negligible gains. Under conditions of air temperature of 40 °C, air velocity of 2 m/s and spray-water temperature of 25 °C, the coefficient of performance increased from 1.53 to 2.74, the heat rejection rate rose by 9.8%, the cooling capacity improved by 33.3%, and the compressor power consumption decreased by 25.9% as the spray-water-to-air-mass flow rate ratio increased from 0.02 to 0.075. Full article

The travertine formed through the precipitation of supersaturated calcium carbonate from geothermal or surface waters due to CO₂ degassing, evaporation, and biological activities not only exhibits remarkable landscape value but also holds significant scientific importance in geological research. Current conservation efforts face critical challenges including travertine degradation, increased algal biomass accumulation, and progressive marshification processes. The study focused on how Vallisneria natans (V. natans) and Ceratophyllum demersum (C. demersum) affected travertine deposition. Analyzing the physical and chemical parameters, phase structure, crystal morphology, and microbial community in the aquatic environment, it was observed that under conditions of low c (Ca²⁺) concentration in solution (≤100 mg L⁻¹), both species significantly increased the rate of travertine deposition. The effect of plant biomass was species-specific: V. natans showed the highest promotion at 70 g L⁻¹, while C. demersum performed effectively at moderate biomass levels (140 and 280 g L⁻¹). Specifically, C. demersum exhibited enhanced photosynthetic activity, elevated pH, increased dissolved oxygen (DO) content and more epibiotic microorganisms, with higher levels of Aeromonas compared to V. natans. Therefore, C. demersum demonstrated a greater capacity for travertine deposition. However, the culture environment with elevated c (Ca²⁺) ≥ 500 mg L⁻¹ or higher biomass levels (420 g L⁻¹) impeded the stable growth of submerged plants and exerted a stress effect on them, hindering travertine deposition. The morphology of travertine crystals promoted by the two submerged macrophytes was distinct. In the V. natans treatment, the crystals were square and elongated, whereas in the C. demersum treatment, they were spheraragonite, droplet-like, and petal-shaped. This study reveals the mechanisms by which submerged macrophytes promote travertine deposition and provides new insights for adopting nature-based ecological restoration strategies to sustainably maintain travertine landscapes. By leveraging the promoting effects of submerged macrophytes, travertine deposition and the aquatic environment were improved while reducing energy and chemical inputs. Such biological regulation approaches help synergistically achieve the dual objectives of geological heritage conservation and ecosystem health restoration. Full article

Liquid is a fundamental requirement for life as we understand it, but whether that liquid has to be water is not known. We propose the hypothesis that ionic liquids (ILs) and deep eutectic solvents (DES) constitute a class of non-aqueous planetary liquids capable of persisting on a wide range of bodies where stable liquid water cannot exist. This hypothesis is motivated by key physical properties of ILs and DES. Many exhibit vapor pressures orders of magnitude lower than that of water and remain liquid across exceptionally wide temperature ranges, from cryogenic to well above terrestrial temperatures. These properties permit stable liquids to exist where liquid water would rapidly evaporate or freeze and outside of bulk phases as persistent microscale reservoirs—such as thin films and pore-filling droplets. In other words, ILs and DES can persist in environments without requiring oceans, thick atmospheres, or narrowly regulated climate conditions. We further hypothesize that ILs and DES could act as solvents for non-Earth-like life, based on their polar nature and the demonstrated stability and functionality of proteins and other biomolecules in ionic liquids. More speculatively, our hypothesis extends to the idea that ILs and DES could enable prebiotic chemistry by providing long-lived, protective liquid environments for complex organic molecules on bodies such as comets and asteroids, where liquid water is absent. Additionally, based on the occurrence of DES-like mixtures as protective intracellular liquids in desiccation-tolerant plants, we propose that ILs and DES might be solvents that life elsewhere purposefully evolves. We review protein and other biomolecule studies in ILs and DES and outline planetary environments in which ILs and DES might occur by discussing available anions and cations. We present strategies to advance the IL/DES solvent hypothesis using laboratory studies, computational chemistry, planetary missions, analysis of existing spectroscopic datasets, and modeling of liquid microniches and chemical survival on small bodies. Full article

The rapid evaporation of liquid droplets across a normal shock wave is a phenomenon of critical importance in advanced propulsion and clean energy systems, such as NH₃ supersonic separation. The conventional Spalding d²-law is commonly used to model such phenomena, but it is not suitable for predicting the complete vaporization of sub-micron droplets, particularly as evaporation approaches the free-molecular regime. To address this issue, this paper introduces a novel time-dependent one-dimensional CFD model, which is used to analyze the shock structure, the non-equilibrium heat and mass transfer between the liquid and gas phases, and the evolution of the droplets’ size through the shock. The model describes the evaporation of NH₃ sub-micron droplet sprays across a stationary normal shock for various fractions of the liquid phase. The Gyarmathy evaporation model is utilized to accurately account for the transition from diffusion-governed to free-molecular regimes, alongside a new two-phase Rankine–Hugoniot shock jump formulation. The study reveals the influence of a steady normal shock on the physical structure of a droplet-laden flow, including the existence of an initial droplet size swelling through the shock, and quantifies the subsequent complete evaporation of the suspended droplets. The maximum swelling throughout the shock is up to 17%, which corresponds to the case with 8% liquid phase mass fraction in the flow. The model provides acceptable accuracy in calculating the two-phase parameters in high-speed flows and can be extended for modeling more complex, multidimensional detonation and propulsion systems. Full article

Vast quantities of liquid hydrocarbon and oil-containing wastes are generated and accumulate annually. Dewatering such sludges presents a significant technological challenge due to the high content of emulsified and chemically bound water. Consequently, the development of integrated approaches, particularly thermomechanical methods, have emerged as a promising strategy. These methods aim to disrupt the emulsion stability and enhance water evaporation efficiency. This study provides a theoretical basis for stabilizing the evaporation of the aqueous phase through mechanical agitation within boiling emulsions. A quantitative mathematical model is developed to identify critical conditions that prevent explosive boiling. Under intensive mixing, water globule diameters decrease by 80–85% within the first 5 s, while their settling time exceeds the dispersion time by hundreds of times—effectively inhibiting the accumulation of a critical aqueous-phase mass. Energy analysis reveals that, at a superheat temperature of 110 °C, the maximum permissible droplet diameter is approximately 0.5 mm; at 150 °C, it must not exceed 0.25 mm to avoid explosive boiling. To ensure safe operation, mixer rotational speeds of at least 100–200 rpm are required, with higher speeds (>200 rpm) necessary near 150 °C. The mechanical agitation modes proposed herein enable controlled, non-explosive evaporation of water from complex emulsions. Collectively, these findings lay a theoretical foundation for the industrial-scale deployment of thermomechanical dewatering technologies—offering a safer, more efficient pathway for managing challenging sludge streams. Full article

This study investigates the effects of deposition angle and arc current on the surface morphology and optical response of Ti coatings obtained by unfiltered cathodic arc evaporation for spectrally selective solar-thermal applications. 100 nm-thick Ti films were deposited at normal (0°) and oblique (80°) angles of incidence, with arc currents of 65 A and 90 A, respectively. The SEM measurements revealed the characteristic arc-generated microdroplet population. At normal incidence (0°), droplets are predominantly spherical and relatively uniformly distributed, whereas at 80° incidence, many droplets exhibit elongated footprints aligned with the incoming flux from the Ti cathode. This behavior is consistent with oblique-angle deposition (OAD), where the arrival geometry can promote self-shadowing and transient droplet spreading before solidification. AFM confirms an increase in nanoscale roughness, whereas GIXRD indicates nanocrystalline α-Ti and cubic TiO, with maximum crystallinity for 0°/65 A. Contact-angle measurements demonstrate a transition from hydrophobic 316L (~103°) to moderately hydrophilic Ti-coated surfaces (~68–72°), with only minor dependence on deposition geometry. Optical reflectance in the 400–800 nm range is significantly lower for Ti-coated glass and is further reduced for OAD films, indicating enhanced solar absorptance. Full article

To reveal the physical evolution of methanol spray under different environmental conditions and injection strategies, this study focuses on the atomization and evaporation behavior of low-pressure methanol spray. The coupled effects of temperature, pressure, and injection parameters are systematically investigated based on constant-volume combustion chamber experiments and three-dimensional CFD simulations. The formation, evolution, and interaction mechanisms of the liquid column core and cooling core are revealed. The results indicate that temperature is the dominant factor influencing methanol spray atomization. When the temperature increases from 255 K to 333 K, the spray penetration distance increases by approximately 70%, accompanied by a pronounced shortening of the liquid-core length and enhanced evaporation and air entrainment. Under low-temperature conditions, a stable liquid-core structure and a strong cooling core are formed, characterized by a high-density, long-axis morphology and an extensive low-temperature region, which suppress fuel–air mixing and ignition. Increasing the ambient pressure improves spray–air mixing but reduces penetration; at 255 K, increasing the ambient pressure from 0.05 MPa to 0.2 MPa increases the spray cone angle by approximately 10% while reducing the penetration distance by about 50%. Furthermore, optimizing the injection pressure or shortening the injection pulse width effectively enhances atomization performance: increasing the injection pressure from 0.4 MPa to 0.6 MPa and reducing the pulse width from 5 ms to 2 ms increases the penetration distance by approximately 30% and reduces the mean droplet diameter by about 20%. Full article

During natural gas field extraction, downhole compressors frequently encounter gas-liquid two-phase flow conditions, yet the internal flow characteristics and performance evolution mechanisms remain insufficiently understood. This paper investigates a small-scale, low-pressure-ratio five-stage axial compressor using a multiphase numerical simulation method based on the Euler-Lagrange framework. The study systematically examines the effects of different inlet pressures (0.1 MPa, 1 MPa, 8 MPa) and liquid mass fraction (0%, 5%, 10%) on its overall and stage-by-stage performance, droplet evolution, and flow field structure. The results indicate that the inlet pressure exerts a decisive influence on the overall efficiency trend of wet compression. The stage efficiency response displays a trend of an initial decrease in the front stages followed by an increase in the rear stages, showing significant variation under different inlet pressures. Flow field analysis reveals that increased inlet pressure intensifies droplet aerodynamic breakup, leading to higher flow losses in the compressor. Simultaneously, under high-pressure conditions, the cumulative cooling effect resulting from droplet heat transfer and evaporation effectively enhances the flow stability in the rear stages. This research elucidates the interstage interaction mechanisms of gas-liquid two-phase flow in low-pressure-ratio multistage compressors and highlights the competing influences of droplet breakup and evaporation effects on performance under different pressure conditions, providing a theoretical basis for the optimal design of downhole wet gas compression technology. Full article