Search Results (190)

Lubricants significantly influence the performance and durability of internal combustion engines (ICEs), yet fresh oils seldom represent in-service conditions. To replicate realistic end-of-life scenarios, lubricants were artificially degraded in sufficient quantities for experimental investigation. This study introduces a methodology to evaluate the impact of altered lubricants on turbocharger dynamics under controlled laboratory conditions. A comparative analysis was performed on turbochargers operating with fresh and aged oils of varying compositions to establish correlations between lubricant properties and vibrational response. Particular attention was given to sub-synchronous phenomena and their implications for rotordynamic stability. Variations in damping and stiffness were assessed under constant pressure and temperature to support mathematical modeling of lubricant degradation and viscosity evolution. Experiments were conducted on a cold turbocharger test bench equipped with acceleration, speed, and displacement sensors, while a mobile oil control unit ensured precise regulation of inlet oil pressure and temperature. Full article

Polar mesocyclones are often the cause of sudden worsening of weather conditions, including strong winds, snowfall with low visibility, and storms. The short lifetime, rapid development, high movement speeds, and small sizes, combined with a lack of meteorological observations over the Arctic seas, create difficulties in forecasting associated weather phenomena. High-resolution numerical modeling can help address this issue. The emergence and development of polar lows (PLs) significantly depend on the properties of the underlying surface, which largely determine the dynamic properties of the atmosphere in the boundary layer. This article is dedicated to assessing the sensitivity of the configuration ICON-Ru of the model ICON with a 2.0 km grid spacing to changes in the sea ice boundary and sea surface temperature (SST) when forecasting the formation and development of PLs. The results showed that the presence of artificial ice in the model almost completely suppresses the development of PLs in cases where the vortex does not have a strong connection with the jet stream. Heating the SST to 278.15 K while simultaneously shifting the ice boundary northward leads to increased thermal instability, rising sensible and latent heat fluxes, and higher CAPE, which enhances PLs, with the degree of enhancement depending on the nature of the vortex formation itself. Full article

A series of experiments were carried out to evaluate different anti-/de-icing approaches for a Pitot probe. Using the Iowa State University Icing Research Tunnel (ISU-IRT), this study compared the performance of a traditional electrically heated system with that of a hybrid concept combining reduced-power electrical heating and a superhydrophobic surface (SHS) coating. The effectiveness and energy efficiency of both methods were assessed. High-speed imaging was employed to capture the transient ice accretion and removal phenomena on the probe model under a representative glaze icing condition, while infrared thermography provided surface temperature distributions to characterize the unsteady heat transfer behavior during the protection process. Results indicated that, due to the placement of the internal resistive heating elements, ice deposits on the total pressure tube were easier to shed than those on the supporting structure. Relative to the conventional approach of maintaining a fully heated probe, the hybrid technique achieved comparable anti-/de-icing performance with substantially reduced power requirements—showing up to ~50% savings during anti-icing operation and approximately 30% lower energy use with 24% faster removal during de-icing. These findings suggest that the hybrid strategy is a promising alternative for improving Pitot probe icing protection. Full article

The phenomenon of surface freezing in lakes, rivers, and reservoirs, has been an essential part of Poland’s winter landscape for centuries. It plays critical ecological roles, such as regulating heat balance and influencing the state of biocenoses. Due to progressive climate warming, we have observed significant changes in ice cover duration, thickness, and timing in recent decades. Ice phenomena on rivers are temporary. They strongly depend on air temperature, which has recently been increasing worldwide. This paper analyzes the variability of ice phenomena formation in selected river profiles of the central Vistula River catchment, central Poland. The research period covers the years 1968–2016. The data come from the Institute of Meteorology and Water Management-State Research Institute (IMGW-PIB). The duration (including the dates of occurrence and disappearance of the phenomenon) and the frequency of occurrence of ice phenomena over the long-term were determined with particular attention to ice cover. The long-term occurrence of ice phenomena shows a decreasing trend (shorter duration, later onset dates) with a simultaneous increase in the average air temperature during the winter half of the hydrological year. Full article

The thermo-hydrological (TH) coupling model constitutes the foundational framework for investigating the temperature distribution of surrounding rock in cold region tunnels. In this study, a fully coupled TH model is proposed that takes into account multiple physical phenomena during the freezing process of surrounding rock. Firstly, the model was established based on thermodynamics, seepage theory, and ice–water phase change theory, which accounted for unfrozen water, latent heat of phase change, ice impedance, and convective heat transfer. The model was successfully verified by comparing its results to field data. Next, the sensitivity of surrounding rock temperature to environmental, thermodynamic, seepage, and coupling parameters in the fully coupled TH model was systematically studied using a numerical analysis method. The results show that the annual temperature amplitude and thermal conductivity represent the main factors affecting the surrounding rock temperature at a radial depth of 0 m, while the initial temperature and porosity are the key factors at a radial depth of 5 m. Permeability has the least influence on the surrounding rock temperature, but the temperature field will experience sudden changes if its value exceeds its value exceeds 1 × 10⁻¹² m². Finally, using the proposed numerical model, the thickness of insulation layer was simulated, and the degree of influence of the parameters on the thickness of insulation layer was analyzed. This study reveals that the annual temperature amplitude has the greatest influence on the calculation of insulation layer thickness, with its normalized sensitivity factor being approximately 50%. These findings not only expand the methodology for exploring the laws of TH coupling but also provide a theoretical foundation for improving the parameter calibration efficiency and calculation accuracy of the fully coupled TH model, and they have significant reference value. Full article

Statistical optimization methods serve as fundamental tools for studying sea-ice-related phenomena in the polar regions. To comprehensively analyze the spatial distributions of ice ridge keels, including the draft and spacing distributions, a statistical optimization model was developed with the aim of determining the optimal keel cutoff draft, which differentiates ice ridge keels from sea ice bottom roughness. By treating the keel cutoff draft as the identified variable and minimizing the relative errors between the theoretical and measured keel spatial distributions, the developed model aimed to seek the optimal keel cutoff draft and provide a precise method for this differentiation and to explore the impact of the ridging intensity, defined as the ratio of the mean ridge sail height to spacing, on the spatial distributions of the ice ridge keels. The utilized data were obtained from observations of sea ice bottom undulations in the Northwestern Weddell Sea during the winter of 2006; these observations were conducted using helicopter-borne electromagnetic induction (EM-bird). Through rigorous analysis, the optimal keel cutoff draft was determined to be 3.8 m, and this value was subsequently employed to effectively differentiate ridge keels from other roughness features on the sea ice bottom. Then, building upon our previous research that clustered measured profiles into three distinct regimes (Region 1, Region 2, and Region 3, respectively), a detailed statistical analysis was carried out to evaluate the influence of the ridging intensity on the spatial distributions of the ice ridge keels for all three regimes. Notably, the results closely matched the predictions of the statistical optimization model: Wadhams’80 function (a negative exponential function) exhibited an excellent fit with the measured distributions of the keel draft, and a lognormal function proved to effectively describe the keel spacing distributions in all three regimes. Furthermore, it was discovered that the relationship between the mean ridge keel draft and frequency (number of keels per kilometer) could be accurately modeled by a logarithmic function with a correlation coefficient of 0.698, despite considerable data scatter. This study yields several significant results with far-reaching implications. The determination of the optimal keel cutoff draft and the successful modeling of the relationship between the keel draft and frequency represent key achievements. These findings provide a solid theoretical foundation for analyzing the correlations between the morphologies of the sea ice surface and bottom. Such theoretical insights are crucial for improving remote sensing algorithms for ice thickness inversion from satellite elevation data, enhancing the accuracy of sea ice thickness estimations. Full article

Understanding the formation, structural evolution, and response of water ice at the nanoscale is essential for advancing research in fields such as cryo-electron microscopy and atmospheric science. In this work, we used environmental transmission electron microscopy (ETEM) to investigate the formation of water ice nanostructures and the etching and charging behaviors of ice under fast electron irradiation. These nanostructures were observed to be suspended along the edges of copper grids and supported on few-layer graphene. We varied growth parameters (temperature and time) to produce water ice nanostructures characterized by uniform thickness and enhanced crystallinity. Moreover, we examined the lithographic patterning of water ice at the copper grid edges and its localized etching effects on graphene substrates. Off-axis electron holography experiments further revealed charging phenomena induced by electron beam irradiation, enabling a quantitative assessment of charge accumulation on the ice nanostructures. Our findings demonstrate the controlled growth of ice thin films under high vacuum conditions at cryogenic temperatures, elucidate the etching behavior and charging phenomena of water ice under rapid electron beam irradiation. Full article

Mathematical models and methods serve as fundamental tools for studying ice-related phenomena in the Yellow River. River ice is driven and constrained by hydrometeorological and geographical conditions, creating a complex system. Regarding the Yellow River, there are some uncertainties that manifest in unique features in this context, including ice–water–sediment mixed transport processes and the distribution of sediment both within the ice and on its surface. These distinctive characteristics are considered to different degrees across different scales. Mathematical models for Yellow River ice developed over the past few decades not only encompass models for the large-scale deterministic evolution of river ice formation and melting, but also uncertainty parameter schemes for deterministic mathematical models reflecting the Yellow River’s particular ice-related characteristics. Moreover, there are modern mathematical results quantitatively describing these characteristics with uncertainty, allowing for a better understanding of the unique ice phenomena in the Yellow River. This review summarizes (a) universal equations established according to thermodynamic and hydrodynamic principles in river ice mathematical models, as well as (b) uncertainty sources caused by the river’s characteristics, ice properties, and hydrometeorological conditions, embedded in parametric schemes reflecting the Yellow River’s ice. The intractable uncertainty-related problems in space–sky–ground telemetric image segmentation and the current status of mathematical processing methods are reviewed. In particular, the current status and difficulties faced by various mathematical models in terms of predicting the freeze-up and break-up times, the formation of ice jams and dams, and the early warning of ice disasters are presented. This review discusses the prospects related to the uncertainties in research results regarding the simulation and prediction of Yellow River ice while also exploring potential future trends in research related to mathematical methods for uncertain problems. Full article

This study investigates the physical interactions and between forest fires and the atmosphere, which often lead to conditions favourable to instability and the formation of pyrocumulus (PyCu). Using the coupled atmosphere–fire spread modelling framework, WRF-SFIRE, the Portuguese October 2017 Quiaios wildfire, in association with tropical cyclone Ophelia, was simulated. Fire spread was imposed via burnt area data, and the fire’s influence on the vertical and surface atmosphere was analysed. Simulated local atmospheric conditions were influenced by warm and dry air advection near the surface, and moist air in mid to high levels, displaying an inverted “V” profile in thermodynamic diagrams. These conditions created a near-neutrally unstable atmospheric layer in the first 3000 m, associated with a low-level jet above 1000 m. Results showed that vertical wind shear tilted the plume, resulting in an intermittent, high-based, shallow pyroconvection, in a zero convective available potential energy environment (CAPE). Lifted parcels from the fire lost their buoyancy shortly after condensation, and the presence of PyCu was governed by the energy output from the fire and its updrafts. Clouds formed above the lifted condensation level (LCL) as moisture fluxes from the surface and released from combustion were lifted along the fire plume. Clouds were primarily composed of liquid water (1 g/kg) with smaller traces of ice, graupel, and snow (up to 0.15 g/kg). The representation of pyroconvective dynamics via coupled models is the cornerstone of understanding the phenomena and field applications as the computation capability increases and provides firefighters with real time extreme fire conditions or predicting ahead of time. Full article

Superhydrophobic surfaces with arrayed pillar structures have huge application prospects in various industrial fields, such as self-cleaning, waterproofing, anti-corrosion, and anti-icing. The knowledge gap regarding the liquid–solid interaction between impacting droplets and microstructured surfaces must be addressed to guide the practical engineering applications more effectively. In this study, the effects of the stationary and horizontally moving superhydrophobic micro-pillar surfaces on the droplet impact dynamic behavioral characteristics are investigated numerically, focusing on the droplet morphology, spreading diameter, contact time, and energy conversion. Based on the numerical simulation results, new prediction correlations of the dimensionless maximum spreading diameter for droplets impacting stationary and horizontally moving micro-pillar surfaces are proposed. Moreover, significant rolling phenomena occur when droplets impact horizontally moving micro-pillar surfaces, which leads to an increase in viscous dissipation and forms a competitive mechanism with the asymmetric spreading–retraction process of the droplets. Two different stages are recognized according to the analysis of the contact time and velocity restitution coefficient. This study may provide new insights into understanding the dynamic behavior of droplets on microstructured surfaces. Full article

Abandoned production and monitoring wells in depleted oil and gas fields can readily serve as primary leakage pathways for stored CO₂. The temperature, pressure conditions around the wellbore bottom, and CO₂ concentration influence the phase behavior of CO₂ during leakage. This study establishes a 3D wellbore–reservoir coupled model using CO₂ injection data from 1 December 2009, in the DAS area, eastern Cranfield oilfield, Mississippi, USA, to analyze the dynamic evolution of CO₂ leakage along wellbores. Simulations are conducted using the collaboration of ECO2M and ECO2N v2.0 modules. The study examines leakage regimes under varying distances from the injection well and different reservoir temperatures. The results indicate that CO₂ phase changes occur primarily in wells near the injection point or under high-pressure and high CO₂ saturation conditions, usually with a short leakage period due to ice formation at the wellhead. In areas with low CO₂ saturation, prolonged leakage periods lead to significant pressure drops at the bottom, as well as the temperature as a result of the Joule–Thomson effect. Lower reservoir temperatures facilitate smoother and more gradual leakage. These findings provide a theoretical foundation for ensuring the safe implementation of CCUS projects and offer insights into the mechanical explanation of CO₂ geyser phenomena. Full article

This study demonstrates changes in the hydrodynamic regime associated with climate change in the southern Baltic over more than 70 years. The analysis of long-term data about sea level, the occurrence of ice cover, waves, and storm surges in the southern Baltic enabled the identification of spatiotemporal variability, including the detection of changes in intensity, frequency, and repeatability of these phenomena. The sea level in the southern Baltic rose by approximately 1 cm/decade from 1886 to 1955. Then, from 1956 to 2019, intensification was observed, and the sea level rose by 1.6 cm/decade and 1.9 cm in the western and eastern parts, respectively. The most intense decadal sea level change in 1955–2019 occurred in March (3.1 cm) and January (2.5 cm), while from July to December, it was at 0.8–1.3 cm. Statistical direct correlation analyses using Spearman’s rank method showed a weak but statistically significant relationship between the mean daily sea level with water temperature and air temperature measured at the same stations. An increase in the frequency of storms in individual decades and a decrease in the number of days with ice was demonstrated. There was no clear trend in the wave conditions regime during the period covered by the analysis in 1980–2021. Full article

This paper describes the development of an ice creation model to be used within the framework of a model-based systems engineering approach to predict the amount of ice growing on aircraft wings during flight. This model supports the preliminary design of the ice protection system, as well as the implementation of a control system, in real-time. When the aircraft meets a high concentration of super-cooled water in the atmosphere and a low temperature, the risk of ice formation on its external surfaces is significant. This causes a decrease in aerodynamic performance, with potential loss of control of the aircraft. To mitigate this effect, ice prevention and protection systems are crucial. The characteristics of the icing phenomena are first defined, then their effects on aircraft behavior during operation are evaluated. This allows us to develop a highly parametric predictive model of the actual icing conditions experienced by the aircraft during a given flight mission. To precisely predict the ice accretion and to design an ice protection system, estimating heat fluxes involving the aircraft’s wing surfaces and the external environment is required. To allow for this, this study also develops a thermal model that is specifically applied to the above-mentioned analysis. This model includes many factors characterizing the atmospheric conditions responsible for ice creation upon the aerodynamic surfaces, and it enables an accurate estimation and quantification of all the parameters necessary to design an appropriate ice protection system. Full article

The information interaction characteristics of connected vehicles are distinct from those of non-connected vehicles, thereby exerting an influence on the conventional traffic flow model. The original lane-changing model for non-connected vehicles is no longer applicable in the context of the new traffic flow environment. The modelling of the new hybrid traffic flow, comprising both connected and ordinary vehicles, is set to be a pivotal research topic in the coming years. The objective of this paper is to present a methodology for optimal mixed traffic flow dynamic modelling and cooperative control in intelligent and connected environments (ICE). The study utilizes the real-time perception and information interaction of connected vehicles for traffic information, taking into account the access characteristics of both connected and non-connected vehicles. The satisfaction-based free lane-changing and mandatory lane-changing models of connected vehicles are designed. Secondly, a mixed traffic flow lane-changing model based on influence characteristics is constructed for the influence area of connected vehicles. This model takes into account the degree of influence that connected vehicles have on non-connected vehicles, with different distances being considered respectively. Subsequently, a vehicle guidance strategy for mixed traffic flows comprising grid-connected and conventional vehicles is proposed. A variety of speed guidance scenarios are considered, with an in-depth analysis of the speed optimization of connected vehicles and the movement law of non-connected vehicles. This comprehensive analysis forms the foundation for the development of a vehicle guidance strategy for mixed traffic flows, with the overarching objective being to minimize the average delay of vehicles. In order to evaluate the effectiveness of the proposed method, the intersection of Gaota Road and Fangshui North Street in Yanqing District, Beijing, has been selected for analysis. The results of the study demonstrate that by modifying the density of the mixed traffic flow, the overall average speed of the mixed traffic flow declines as the density of vehicles increases. The findings reported in this study reflect the role of connected vehicles in enhancing road capacity, maximizing intersection capacity and mitigating the occurrence of queuing phenomena, and improving travel speed through the mixed traffic flow lane-changing model based on impact characteristics. This study also provides some guidance for future control of the mixed traffic flow formed by emergency vehicles and social vehicles and for realizing a smart city. Full article

We propose the hypothesis that dune gullies and seasonal “meteorological” appearances observed on the same dunes (e.g., frosting) may have a common origin. These gullies are difficult to explain through the action of liquid flow. The occurrence of a spring flowing from the crest of a dune seems impossible to explain. However, these phenomena could originate from the impact of wind on the profiles of some large Martian dunes. This aerodynamic effect could seasonally generate all the meteorological phenomena we observe on these dunes (bodies of ice, frost, moisture trails, and vapor clouds) and as a result, produce gullies with a peculiar morphology different from the standard. Thus, dune gullies could originate from meteorological liquids, but through a process unlike those known on Earth. Evidence from the Kaiser, Russell, and Korolev Craters supports the possibility of a partial water cycle (a half-cycle), potentially the remnant of a complete ancient cycle. Full article