Mass Source Research Articles

An experimental platform for investigating astrophysically relevant magnetized plasma jets on the COBRA facility

A new platform has been developed for the 1-MA COBRA generator to investigate the physical processes affecting the formation, collimation, and stability of high-speed outflows in magnetically driven laboratory plasma jets. Such experiments serve as diagnostically accessible surrogates for astrophysical jets under the assumption that the underlying dynamics are scale invariant. In contrast to previous current driven high energy density laboratory jet experiments that use radial/conical wire arrays or foils, the platform described here uses azimuthally symmetric gas-puff injection. This avoids the ablation phase from a solid target, allowing the jets to develop earlier and be driven longer without depleting their mass source and disrupting. A permanent magnet provides an initial poloidal magnetic field, which links the two concentric electrodes and mimics the boundary conditions of a star-accretion disk system. Extended magnetohydrodynamic effects can be assessed using a polarity convolute, which allows for reversal of the electrode bias. The resulting plasma jets exhibit remarkable stability, persisting for hundreds of nanoseconds and achieving aspect ratios ≳30:1.

Mass load and source apportionment of pharmaceutical and personal care product in the Wuhan section of the Yangtze River, China.

Given the limited research on pharmaceuticals and personal care products (PPCPs) in the Wuhan section of the Yangtze River (WYR), this work investigated the distribution of 15 PPCPs in this region, assessed their ecological risks and annual fluxes. It was further to analyze the levels of indicator sucralose in the WYR to understand the sources of PPCPs. The results showed the average concentrations were 143.9±76.77ng/L, 3.98±3.89ng/g, and 8.14±18.91ng/g for 15 PPCPs in surface water, sediment, and soil, respectively. Among those PPCPs, bisphenol-A was the dominant compound found across the three environmental media. Significant amounts of ibuprofen and caffeine were detected in surface water, which may be linked to the increased demand for these compounds during the COVID-19 pandemic. Besides, the concentrations of synthetic estrogens (bisphenol-A and 4-nonylphenol) were higher than those of natural estrogens (estrone, 17β-estradiol, and estriol). Due to runoff dilution, climatic factors (rainfall and sunlight), and prevalence of disease, PPCPs in water showed significant seasonal variation, with higher total concentrations in dry season than those in wet and normal seasons. Spatially, higher concentrations of PPCPs were found in the middle reaches of the WYR due to the population density.Our study estimated the annual flux of 15 PPCPs in the WYR to be 71.17 tons. Source analysis revealed that untreated domestic wastewater might be discharged into the WYR during the wet season. The ecological risk of PPCPs in the WYR were generally low, with only E2 and E3 categorized as posing moderate to high risks. These findings provided valuable support for the management and control of PPCPs in the WYR.

Environmental Problems in Mining Quarries and Theoretical and Practical Comparison of Dust Emissions

This study reveals that the development of the country is only possible through meticulous analysis of regional potentials and sustainable use of natural resources. The aim of this study is to evaluate the environmental impacts arising from the site selection of mining operations and to put forward the necessary measures for the efficient and controlled use of natural resources within the scope of sustainable development. In this context, the importance of factors such as expropriation, topography, environmental conditions and energy and water access in the site selection of mines is emphasized. In the study, the AERMOD model developed by the United States Environmental Protection Agency for air quality modeling was used to estimate the environmental impacts of dust emissions that may occur during mining activities. In the modeling process, data on pollutant sources such as mass flow rate, source height and gas outflow rate were combined with meteorological data and calculated according to the Regulation on the Control of Industrial Air Pollution. In addition, in-plant PM10 measurements were performed and analyzed by gravimetric method. As a result, the modeling studies and the data obtained serve as a basis for the environmental permitting process of the facilities that will be put into operation and provide guidance to decision makers for air quality management. The study also emphasizes the importance of assessing the cumulative air quality impacts of existing facilities and demonstrates that verifying these impacts with reliable laboratory studies will contribute to sustainable development targets.

Villages of the Black Earth Region of European Russia in the 17th – First Third of the 18th Centuries

Introduction. In the 17th century, in the south of European Russia, in the Black Earth districts, the process of economic development of vast fertile lands took place. The effectiveness of this process was associated with the increase in the number of Russian settlers to work on arable land. Economic success played an important role in the confrontation between Russia and the Crimean Khanate. The war between the two states lasted throughout the 17th century. In recent decades, the study of the history of the development of black earth districts in Russia has continued in various directions, but the problem of economic development of new territories remains relevant for study. Methods and materials. The authors of the article use data on the number of villages as a criterion for assessing the process of reclamation of empty lands. The authors focus on the villages of the three largest regions of the Black Earth region – the Belgorod, Voronezh, and Yelets regions. Materials from the Kozlov region are used as additional information. The materials for the work were mass sources – census books of the 17th – first quarter of the 18th centuries. Results. As a result of the study, an increase in the number of rural settlements and changes in their internal structure were recorded in favor of the increase in large villages. All this testifies to Russia’s economic success in the region and allows us to understand some of the features of this process. There is also no doubt about the steady demographic growth throughout the 17th century. These factors played an important role in the struggle for the annexation of the Black Earth Strip to Russia during periodically escalating military conflicts and political confrontations. Contribution of the authors of the article: D.A. Lyapin – concept development, writing of the introduction, analysis of the results. A.R. Melnikova – processing of materials for the article, writing of the section “Materials and methods,” design of the article. D.A. Lyapin – 50%, A.R. Melnikova – 50%. Funding. The research was carried out at the expense of a grant from the Russian Science Foundation (project No. 24-68-00011, https://rscf.ru/project/24-68-00011/) on the basis of Bunin Yelets State University.

Thermo- and soluto-capillary convection and instability near the air–liquid interface

Steady thermo- and solute-capillary convection, instability, and pattern evolution near the air–liquid interface driven by point heat and mass sources are investigated. First, under the assumption of the conically similar viscous flow, an exact axi-symmetric solution of the steady thermo- and soluto-capillary convection near the air–liquid interface is determined due to the constant heat and mass fluxes. It is shown that the constant heat, mass fluxes, and the radial surface tension cause the divergent motion at the interface and the Marangoni convection beneath the interface. Then, the linear stability of the steady thermo- and soluto-capillary convection in response to the azimuthal disturbance is analyzed. At a given Peclet (or Schmidt), Marangoni (or Prandtl), and elasticity numbers, the steady basic flow loses its stability when Reynolds number is beyond the critical value. It is found that for small Schmidt numbers, a half-loop structure between the critical Reynolds number and the harmonic wave number of the azimuthal disturbance appears. For large Schmidt numbers, the critical Reynolds number monotonously increases as the harmonic wave number increases. The critical patterns of the velocity fields and the isothermal, iso-concentration lines in the three-dimensional flow system in response to the disturbance harmonic wave number are dominated by both the radial and azimuthal surface tensions. The results not only provide a valuable understanding of Marangoni convection and pattern information near the air–liquid interface but also inspire its potential practical applications in the material chemistry and biotechnology.

Gradient-constrained algorithm for simulating bubble growth in microchannel boiling flow using volume of fluid method

Gradient-constrained algorithm for simulating bubble growth in microchannel boiling flow using volume of fluid method

The microlayer and force balance of bubbles growing on solid in nucleate boiling

The microlayer and force balance of bubbles growing on solid in nucleate boiling

Dynamic response of rock landslides and avalanche debris flows impacting flexible barriers based on shaking table tests

Dynamic response of rock landslides and avalanche debris flows impacting flexible barriers based on shaking table tests

Investigation of bubble interaction in a temporal and spatial heat flux partitioning model for subcooled flow boiling

Investigation of bubble interaction in a temporal and spatial heat flux partitioning model for subcooled flow boiling

Precipitation in the mountains of Central Asia: isotopic composition and source regions

Abstract. Over 900 event-based precipitation samples were collected in 2019–2021 in the Tien Shan and its foothills and analysed using cavity ring-down spectroscopy. δD and δ18O values were highest in summer and lowest in winter, and annual cycles of deuterium excess (d-excess) varied between sites, reflecting local conditions. The δ18O and δD values increased from north to south in all seasons except autumn, and latitude was a statistically significant predictor of δ18O and δD in the overall data set, along with elevation in winter and elevation and longitude in autumn. Elevation was a significant predictor of d-excess in all seasons, and local air temperature was a more important control over δ18O and δD than precipitation depth. Local meteoric water lines were derived using seven regression methods applied to non-weighted and weighted precipitation. Non-weighted ordinary least squares regression and reduced major axis regression methods are recommended overall, except for summer when the precipitation-weighted least squares regression should be used, particularly in the south. Atmospheric back-trajectory and mixing-model analyses were applied in combination to identify air mass source regions and their relative contribution to precipitation. Recycled moisture from irrigated land in the Amu Darya and Syr Darya basins and from the study catchments accounted for 29 %–71 % of precipitation, depending on the site and season. In the Chon Kyzyl-Suu catchment, local re-evaporation from Issyk-Kul accounted for up to 85 % of precipitation. These findings highlight the importance of moisture from terrestrial sources, especially irrigated land, for the formation of precipitation in the Tien Shan.

Volumetric and Entropic Sound Sources of Helmholtz Resonators with Different Temperatures

This study proposes an acoustic analogy model for the Helmholtz resonator (HR)–combustor system, considering the temperature difference between the bias flow from the HR and the grazing flow inside the combustor duct. The model highlights how the mass flux of the bias flow and the temperature difference serve as mass and entropic sound sources, respectively, influencing the HR’s sound absorption performance. To validate the model, we conducted numerical simulations using the Reynolds-averaged Navier–Stokes shear stress transport model to obtain the mean flow, followed by solving the frequency-domain linearized Navier–Stokes equations in COMSOL. The model was tested with HRs attached to combustor ducts under open–open and open–closed boundary conditions. Theoretical results agree well with numerical simulations, confirming the model’s accuracy. Results indicate that when the bias flow temperature is lower than the grazing flow temperature, the entropic sound source negatively affects duct acoustics, reducing sound absorption performance. Conversely, higher bias flow temperatures enhance sound absorption by superimposing entropic and mass-related sound sources. Additionally, the overall effect of the mass-related and entropic sound sources is equal to a volumetric source which depends on the mean sound speed and density of the HR instead of those of the combustor.

Modelling of planetary accretion and core-mantle structure formation

Abstract We advance a thermodynamically consistent model of self-gravitational accretion and differentiation in planets. The system is modeled in actual variables as a compressible thermoviscoelastic fluid in a fixed, sufficiently large domain. The supply of material to the accreting and differentiating system is described as a bulk source of mass, volume, impulse, and energy localized in some border region of the domain. Mass, momentum, and energy conservation, along with constitutive relations, result in an extended compressible Navier–Stokes-Fourier-Poisson system. The centrifugal and Coriolis forces are also considered. After studying some single-component setting, we consider a two-component situation, where metals and silicates mix and differentiate under gravity, eventually forming a core-mantle structure. The energetics of the models are elucidated. Moreover, we prove that the models are stable, in that self-gravitational collapse is excluded. Eventually, we comment on the prospects of devising a rigorous mathematical approximation and existence theory.

Aerosol Vertical Turbulent Mass Flux Retrievals Through Novel Remote Sensing Algorithm

AbstractIntegrated measurements of aerosol, radiation, cloud, and turbulent transport in the planetary boundary layer (PBL) are essential for understanding and modeling climate and air quality. Here, we developed a new technique for the identification of convective turbulent regions and deriving the vertical distribution of aerosol turbulent mass fluxes within PBL. The algorithm uses retrievals from coherent Doppler lidars and a high spectral resolution lidar. The technique was applied to study particle mass fluxes over 2 months (November–December 2020) during the campaign conducted at the DOE Atmospheric Radiation Measurement Southern Great Plains (SGP) site in Lamont, Oklahoma. The algorithm developed here is capable of continuously deriving vertically resolved (curtains) aerosol mass fluxes. Our data analysis shows that at the site, the 30‐min averaged fluxes at 135 m above the surface were mainly positive (upward) at ∼1 μg m−2 s−1, suggesting that the surface is the primary source of the particle mass supplied to the boundary layer at the SGP site. Analyses of the individual case studies have revealed that not all the derived fluxes can be linked to surface emissions. Both positive and negative values in a range of ±5 μg m−2 s−1 can be caused by convective thermals interacting between the residual layer and the mixed layer and by rotation of the horizontal wind with the height. Large erroneous negative fluxes can also be caused by drizzling/precipitating clouds. We anticipate that the application of the current technique will lead to a more realistic representation of aerosol mass budgets and bidirectional mixing rates.

An adaptive internal mass source wave-maker for short wave generation

An adaptive internal mass source wave-maker for short wave generation

Influence of Dilution and Effusion Flows in Generating Variable Inlet Profiles for a High-Pressure Turbine

Abstract The elevated flow temperatures and pressures exiting gas turbine combustors affect the efficiency and durability of the high-pressure turbine stage. Understanding the effects that result from the upstream dilution and effusion flow interaction in creating the combustor exit profiles is important to advancing gas turbines. Understanding how common combustor features, such as dilution jets and effusion cooling, interact based on computational predictions guided the design of a non-reacting profile simulator capable of producing a wide range of non-uniform temperature profiles representative of those entering high-pressure turbines. The mechanical design of a new simulator device, which will be experimentally tested in the future, is presented in this paper along with computational predictions of flow and thermal fields. The simulator was designed for modular installation into the Steady Thermal Aero Research Turbine (START), which is a continuous-duration, steady-state turbine facility that houses a single-stage test turbine. Features of the simulator included interchangeable liner panels with multiple rows of dilution jets and wall effusion cooling to study various hole diameters and patterns. The dilution jets generate elevated turbulence intensities and tailor the temperature profiles in the radial and circumferential directions. The air mass flow distribution and source flow temperatures are independently controlled. To aid in the simulator design, computational fluid dynamics (CFD) simulations using Reynolds-averaged Navier–Stokes modeling were conducted with a two-level Design of Experiments (DOE) approach to determine a number of engine-representative target profiles with temperature shapes that are mid-radius peaked, outer-diameter peaked, inner-diameter peaked, and uniform. A sensitivity analysis of the CFD DOE results determined which factors significantly affected the profile shape so that the target profiles could be produced. The analysis indicated that the main contributor to the temperature profile shape at near-wall vane radial span locations of 0–15% and 85–100% was the injection temperature of the effusion flow. The main contributor at radial span locations of 15–40% and 60–85% was the injection temperature of the third-row dilution jets, and at the mid-radius location of 40–60% vane radial span, the main contributor was the diameter of the first-row dilution holes.

A Simple Model for Multiple Equilibria in Ice-Covered Oceans

Abstract The existence of multiple equilibria (ice-covered and ice-free states) is explored using a set of coupled, nondimensional equations that describe the heat and salt balances in basins, such as the Arctic Ocean, that are subject to atmospheric forcing and two distinct water mass sources. Six nondimensional numbers describe the influences of atmospheric cooling, evaporation minus precipitation, solar radiation, atmospheric temperature, diapycnal mixing, and the temperature contrast between the two water masses. It is shown that multiple equilibria resulting from the dependence of albedo on ice cover exist over a wide range of parameter space, especially so in the weak mixing limit. Multiple equilibria can also occur if diapycnal mixing increases to O(10−4) m2 s−1 or larger under ice-free conditions due to enhanced upward mixing of warm, salty water from below. Sensitivities to various forcing parameters are discussed. Significance Statement The purpose of this study is to better understand under what circumstances high-latitude seas, such as the Arctic Ocean, can exist in either an ice-covered or an ice-free state. The temperature and salinity of the ocean, as well as the heat exchange with the atmosphere, are drastically different depending on which state the ocean is in. The theory presented here identifies how forcing from the atmosphere and ocean dynamics determines whether the ocean is ice covered, ice free, or possibly either one.

Two-temperature thermochemical nonequilibrium model based on the coarse-grained treatment of molecular vibrational states.

Although the high-fidelity state-to-state (StS) model accurately describes high-temperature thermochemical nonequilibrium flows, its practical application is hindered by the prohibitively high computational cost. In this paper, we develop a reduced-order model that leverages the widelyused two-temperature (2T) framework and a coarse-grained treatment of molecular vibrational states to achieve accuracy comparable to the StS model while ensuring computational efficiency. We observe that the multigroup coarse-grained model (CGM), lumping vibrational energy levels into several groups, yields results close to the StS model for the high-temperature postshock oxygen flows, even using only two groups. However, theone-group CGM (CGM-1G), equivalent to the 2T model but using the StS kinetics, fails to approximate the StS results. Analysis of microscopic group properties reveals that the failure of the CGM-1G stems from the inability to capture the non-Boltzmann effects of mid-to-high vibrational levels, overestimating apparent dissociation rates and vibrational energy loss in the dissociation-dominated region. We then propose an analytical distribution function of vibrational groups by incorporating Treanor-like terms and an additional linear term (addressing the dissociation depletion of high-lying levels). Building upon this algebraic group distribution function and reconstructing vibrational levels within each group using the vibrational temperature, we develop a new 2T model called CG2T, which demonstrates accuracy much closer (than the CGM-1G) to the StS results for the postshock oxygen flows with varying degrees of thermochemical nonequilibrium. Moreover, a fullyconnected neural network is pretrained to substitute the module for the mass and vibrational energy source terms to enhance computational efficiency, achieving about 30-fold speedup in the CG2T model without sacrificing accuracy.

Heat transfer and flow of molten pool in single track multi-layer aluminum alloy laser wire additive manufacturing

Heat transfer and flow of molten pool in single track multi-layer aluminum alloy laser wire additive manufacturing

Generation of nonlinear gravity waves based on the harmonic polynomial cell method incorporated with a mass source

Generation of nonlinear gravity waves based on the harmonic polynomial cell method incorporated with a mass source

A Portable Passive Ankle-Foot Orthosis for Walking Propulsion and Drop-Foot Prevention

Abstract Individuals with a drop-foot generally have issues of foot-slap and toe-drag, and ankle-foot orthoses (AFOs) have been developed for them to address the drop-foot gait. However, the currently available active AFOs usually have heavier mass, larger volume, and additional power sources, and almost all of the passive AFOs can achieve dorsiflexion assistance at the cost of making plantarflexion more difficult, which increases the wearer's metabolic cost of walking. This paper illustrates the development and validation of a passive AFO for walking propulsion and drop-foot prevention of individuals with a drop-foot gait. The AFO is primarily composed of a propulsion module, a drop-foot prevention module, and a support module. The propulsion module can detect the wearer's gait stages, and it can control the energy storage and release of an energy storage spring-A by switching the state of a clutch-A mechanism. The drop-foot prevention module is designed to correct the abnormal gait of individuals with a drop-foot gait during the swing phase. Experiments are conducted to evaluate the performance of the developed AFO. The experimental results demonstrate that during a gait cycle, reductions of 7.74%, 6.72%, and 16.36% of the average muscle activities of the gastrocnemius, soleus, and tibialis anterior are observed, respectively. The significance of this study is the development of a portable passive AFO that has the potential to provide plantarflexion assistance and dorsiflexion assistance for the wearers during the late stance phase and swing phase, respectively.