Flow Model Research Articles

Transport and competitive interfacial adsorption of PFOA and PFOS in unsaturated porous media: Experiments and modeling

Among emerging contaminants, per- and polyfluoroalkyl substances (PFAS) have captured public attention based upon their environmental ubiquity and potential risks to human health. Due to their typical surface release conditions and amphiphilic properties, PFAS tend to sorb to soil and accumulate at the air-water interface within the vadose zone. These processes can result in substantial plume attenuation. Although there is a growing body of literature on vadose zone transport, few studies have explored PFAS mixture transport, particularly under conditions where nonlinear sorption processes are important. The present study aims to advance our understanding of PFAS transport in variably saturated porous media through integration of experiments and mathematical modeling. Experiments include batch studies to quantify sorption to the solid phase, interfacial tension (IFT) measurements to estimate adsorption at the air-water interface (AWI), and column studies with F-70 Ottawa sand at 100 % and ca. 50 % water saturation to explore transport mechanisms. Employed PFAS solutions encompass individual solutes and binary mixtures of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentration levels spanning four orders of magnitude to assess competitive and nonlinear sorption at the AWI. Observations demonstrate that concentration levels and competitive effects substantially influence PFAS transport in unsaturated systems. In the presence of PFOS, PFOA experienced less retention than would be anticipated based on single-solute behavior, and effluent breakthrough curves exhibited chromatographic peaking. The presented mathematical model for simultaneous flow and transport of PFAS was able to capture experimental observations with a consistent set of parameters and minimal curve fitting. These results demonstrate the robustness of the model formulation that included rate-limited interfacial mass transfer, an extended Langmuir-Szyszkowski model for adsorption at the AWI, and a scaled Leverett thermodynamic model to predict the AWI specific area. Overall, the results of this work underscore the importance of the AWI in PFAS transport and highlight the relevance of competition effects in adsorption formulations.

Financial Management Model in Realizing the Economic Independence of Islamic Boarding School

Islamic boarding schools are non-profit organizations. In its development, Islamic boarding schools are not only institutions that only concentrate on tafaqquh fiddin, but also develop businesses in order to realize economic independence, so that Islamic boarding schools do not depend on other institutions or on student contributions. However, the problems faced are, first, how is the financial management pattern applied in order to realize the economic independence of Islamic boarding schools? second, what are the forms of economic independence of Islamic boarding schools that have been realized? This study uses a qualitative approach with a case study type. This study took the object at PP. Manbaul Ulum Wonosari Bondowoso. Data were collected using observation, interview and documentation techniques. Data were analyzed using the flow model stages from Miles and Huberman. The data validity test used triangulation of sources, techniques and time. So that the results obtained, first, that the financial management model of Islamic boarding schools is directly led by the Kiai, the management is handed over to trusted administrators. There is a planning process through budgeting, implementation, supervision and evaluation. The decision maker is the Kiai as the central leader of the Islamic Boarding School. Second, the form of economic independence of Islamic boarding schools is realized through the formation of business units such as banner printing, photocopying business, book store, uniform store, grocery store, santri cooperative, food stall/canteen, stationery store, reception decoration, and Ambarsa Mart. The profit from these businesses is managed for the needs of the Islamic boarding school. So, economically the Islamic boarding school has independence.

Limitations of Flow Model Due to Geometric Differences Between Gravity and Electric Potential Difference

Limitations of Flow Model Due to Geometric Differences Between Gravity and Electric Potential Difference

Complex Traffic Flow Model for Analysis and Optimization of Fuel Consumption and Emissions at Large Roundabouts

Complex Traffic Flow Model for Analysis and Optimization of Fuel Consumption and Emissions at Large Roundabouts

Study on the Migration Mechanism of Temporary Plugging Agent in Artificial Fractures of Deep Geothermal Reservoirs Based on the Euler-Euler Multiphase Flow Model

The successful use of temporary plugging diverting fracturing technology requires an understanding of the migration and plugging processes of temporary plugging agents into artificial fractures under high temperature settings. In this study, a multiphase flow model for the migration of temporary plugging agents in artificial fractures was developed using the Euler-Euler framework, and numerical simulations were conducted at elevated temperatures. Various factors, including plugging agent injection velocity, concentration, carrying fluid viscosity, wall temperature, and fracture width, were systematically analyzed to assess their impact on the agent’s migration behavior. Detailed analyses, using cloud diagrams of particle volume fraction, velocity, and turbulence intensity, clarified the underlying mechanisms influencing the migration process. The results indicate that as the injection velocity increases, the height of blockages near the wellbore decreases, while the blockage length initially increases before declining. Increasing the concentration of the plugging agent leads to a rise in blockage height and a shift in the front edge toward the injection point. Enhancing the viscosity of the carrying fluid enables the plugging agent to migrate deeper into the fracture, improving deep plugging effectiveness. While changes in wall temperature have limited impact on blockage morphology, temperatures exceeding the critical threshold of 573K significantly intensify particle migration. Moreover, increasing fracture width enhances both the height and length of blockages, with the optimal plugging effect observed when the plugging agent diameter is approximately one-third of the fracture width.

An Elastohydrodynamic model of the slot-die coating process

Abstract The slot-die coating process plays an important role in the industry, as it is employed in many different fields. The characteristics of the final application are determined by the flow between the die and the roller. This research paper aims to develop a mathematical model of such flow that takes into account the roller deformations caused by high pressure values reached by the coating fluid. This Elastohydrodynamic model is made up of a coupling between the mathematical model of the flow and the mathematical model of the roller deformations. Model resolution is undertaken numerically by deforming the flow domain according to the roller deformations using computational fluid dynamics (CFD) and computational solid mechanics (CSM) techniques. For its part, the finite volume method (FVM) is used to perform the flow model analysis while the finite element method (FEM) is employed to deal with roller deformations. The results obtained from this model give information on the flow pressure distribution, coating gaps, meniscus position, extent of roller deformations in the coating flow and the influence of different operating conditions. The information obtained from this study is valuable for industrial applications, as it gives insights into the coating process that can help manufacturers to define a suitable combination of operating parameters in order to obtain coating applications that meet quality and performance requirements.

Analysis of mathematical methods for describing financial flows: dynamic modeling of an innovative company

Purpose. Development of a dynamic mathematical model of an innovative company operating in accordance with Ukrainian legislation, allowing for the analysis and adjustment of its financial activities. Methodology. When developing a model and description of financial flows, a factor analysis of the necessary indicators of the financial condition of the enterprise in question was carried out, which were used in the calculations of the presented mathematical modeling. A mathematical apparatus has been developed for calculating financial indicators depending on time. Using inductive, deductive and logical methods, an analysis of the financial situation for the year was carried out. Findings. The main methods and tools for describing financial flows have been analyzed. Mathematical modeling of the innovative company is carried out, which allows analyzing the costs of the enterprise and determining the size of its free funds. The calculation of financial indicators of the enterprise, which are demonstrated in the form of tables, is performed and the dynamics is shown in charts and graphs. All calculations were made on the basis of existing Ukrainian legislation using modern information technologies. Originality. A mathematical dynamic model of changes in financial flows at the enterprise has been developed and implemented. The proposed model takes into account various items of expenses and profits in accordance with the state legislation. Calculations allow for dynamic analysis and determination of the impact of various indicators on the financial condition of the enterprise, which allows for faster adoption and implementation of decisions in managing financial flows. This dynamic model is a convenient tool for any enterprise in Ukraine. Practical value. The results that were obtained during the study can become the basis for creating the necessary digital tools for researching, analyzing and adjusting the financial flows of a particular enterprise. Now methods are available that allow analyzing and describing financial flows more accurately and forecasting their changes in the future. The methodology presented allows the creation of dynamic models that can account for complex dependencies between different indicators and forecast the behavior of financial flows in real time. The financial model allows the simulation of cash flows of planned activities and the evaluation of financial planning in advance, taking into account the conducted research. It is straightforward to use and allows the analysis of different scenarios of business development, significantly reducing the time required.

Thermal Exploration of Combined Rectangular and Semi-Circular Artificial Ribs in the Flow Regime of Solar Air Heater: A Computational and Experimental Approach

Abstract A roughened solar air heater is developed numerically and experimentally with a novel roughness in the absorber. The roughness incorporated is a combination of rectangular and semi-circular ribs. The analysis is done to improve the thermal characteristics considering two cases. Type A with ribs placed above the absorber and Type B with ribs placed below it. Several operating parameters are investigated including heat flux, Reynolds number (Re), relative obstacle relative height (h/H) ranging from 400 W/m2 to 1000 W/m2, 4000 to 10,000, and 0.4 to 1.0, respectively. The relative pitch is kept constant at 15 mm. The governing equations are simulated employing the renormalization group k–ε turbulence flow model. The results indicated that both Type A and Type B achieved significant improvements over the smooth duct. Type A exhibited a maximum Nusselt number of 4.24, while Type B achieved 3.93 in comparison with smooth duct at Re of 10,000, respectively. The thermal enhancement factor (TEF) ranges from 1.32 to 1.79 for Type A and 1.26 to 1.69 for Type B at a heat flux intensity of 1000 W/m2. Also at a relative height of 1.0, Type A demonstrated the highest TEF of 1.79 at Re = 10,000 and provided a maximum exergy efficiency of 11.2%.

Modelling hazards impacting the flow regime in the Hranice Karst due to the proposed Skalička Dam

Abstract. This study examines the hydrogeological hazard associated with the construction of the proposed Skalička Dam in the vicinity of the Hranice Karst. Prompted by the catastrophic regional floods in 1997 and 2010, the design of the dam aims to mitigate floods along the Bečva River downstream of the reservoir. However, concerns have been raised regarding the potential disturbance of the natural groundwater regime in the Hranice Karst and the source of mineral waters for the Teplice spa. This is due in particular to the dam's location in an area with limestone outcrops potentially susceptible to surface-water infiltration. Previous studies have also highlighted the strong correlation between the water level in the Bečva River and the water level in karst formations such as the Hranice Abyss, Zbrašov Aragonite Caves, and other caves in the locality. To address these concerns, a nonlinear reservoir-pipe groundwater flow model was employed to simulate the behaviour of the Hranice Karst aquifer and specifically the effects of the dam reservoir's impoundment. The study concluded that the lateral variant of the dam would have a practically negligible impact on the karst water system, with the rise in water level being only a few centimetres. The through-flow variant was found to have a more significant potential impact on water levels and the outflow of mineral water to the spa, with a piezometric rise of about 1 m and an increase in the karst water discharge to the Bečva River of more than 50 %. Based on these results, recommendations for further investigations concerning the design of the dam and its eventual construction have been formulated to reduce geological uncertainties and to minimize the potential impact of the hydraulic scheme on the hydrogeology of the karstic system.

Modeling and Simulation of Vehicle Velocity-Density on Buah Batu Road Using Decision Tree Regression

This study aims to explore and simulate the traffic flow model on Buah Batu Road using the velocity-density function generated by the Decision Tree Regression method. The model utilizes a macroscopic approach, specifically the Lightill, Whitham, and Richards (LWR) model, which considers vehicle interactions. Observational data were collected directly from Buah Batu Road and processed to produce a velocity-density function, which shows that vehicle speed decreases as density increases, following a non-linear but step-like pattern. The velocity function generated by the Decision Tree Regression indicates that for low density (ρ < 0.102), the average speed is predicted to be around 3.681 to 4.551, while at high density (ρ > 0.273), the speed drops to around 1.411 or lower. The simulation was conducted on a 60-meter road segment with a total simulation time of 5 minutes and a grid resolution of 300 points. At the beginning of the simulation, a peak density of 0.70 was recorded in the 15-25 meter segment, which then shifted and decreased to 0.50 in the 30-50 meter segment by the end. The results indicate that vehicle movement reduces density and improves traffic flow. Thus, the Decision Tree Regression method has proven effective in modelling and simulating the velocity-density relationship to understand traffic dynamics on Buah Batu Road.

Comprehensive Theoretical Formulation and Numerical Simulation of the Internal Flow in Pressure-Swirl Atomizers Type Screw-Conveyer

The present work shows the development of a comprehensive theoretical formulation for its application in the study of the internal flow of pressure-swirl atomizers with helical channels: “screw-conveyer”, which are characterized by presenting in their inlet channels, an angle of incidence or helix angle ψ. This angle originates a trigonometric factor (cosψ) that must be considered in the geometrical characteristics parameter of pressure-swirl atomizer (Ah), which consequently involves other geometric parameters, such as the annular section coefficient (φ), discharge coefficient (Cd), spray angle (2α), etc., being relevant in the internal flow study and design of the pressure-swirl atomizers type screw-conveyer. This theoretical formulation integrates an internal ideal flow model (Abramovich theory) with a model that considers the influence of the liquid viscosity (Kliachko theory) and hydraulic resistance of Idelchik. For the validation of this theoretical formulation, numerical simulation was used, considering the commercial software Ansys Fluent 2023 R2 furthermore, hexahedral meshes were generated with the ICEM CFD software 2023, for four cases of helix angle ψ (15°, 30°, 45° and 60°), with application of the RNG k-ε turbulence model and VOF multiphase model (volume of fluid) for the location of the liquid-gas interface and spray angle visualization.

Collaborative work processes in establishing a MiniMaria treatment center for youth substance addiction: a qualitative inquiry of county council healthcare and municipal efforts

BackgroundThis article is part of a larger study exploring the collaborative dynamics between key stakeholders in providing care to youths suffering from alcohol or substance use and their families in formulating policies and operational practices for county and country-wide application in similar settings. The focus of this article is to describe the collaborative processes between two stakeholders, a municipality, and a county council, in establishing a MiniMaria treatment center. While collaborative efforts between municipalities and county councils in health service provision are often acknowledged, little is known about how communication and decision-making processes between these entities shape the success of such initiatives. This study aims to fill this gap by providing insights into the communicative processes that foster organizational cohesion, agility, and innovation. The guiding research question is: What communicative processes occur between the county council and municipal stakeholders during the planning phase of the MiniMaria treatment center?MethodsThe municipality and county council were selected based on purposive sampling, owing to the proximity and accessibility of the field. An exploratory and descriptive design, incorporating a participatory research approach, was employed for this qualitative investigation.ResultsTwo central themes, each underpinned by specific subthemes sum up the essence of our findings. The first theme underscores the collaborative dynamics and shared objectives that have emerged through the project, thus showing the importance of a unified vision and mutual understanding in driving the initiative forward. The second theme points to the practical aspects of implementing the project, including recruitment strategies, and the significance of interpersonal communication.ConclusionsThis article sheds light on the establishment of a MiniMaria treatment center through collaboration between a municipality and county council, using the Four Flows Model to interpret communicative processes. Membership negotiation was crucial for defining roles and building a unified team identity, while activity coordination ensured aligned stakeholder efforts. Self-structuring facilitated internal organization and operational clarity, and institutional positioning aligned the initiative with broader healthcare norms, enhancing its credibility and impact. These communicative practices were central to get a grip on inter-organizational complexities, emphasizing communication’s constitutive role in organizational development and innovation.

Estimation of glacier-stored freshwater volume present in major tributaries of the Brahmaputra basin.

Estimation of the glacier-stored freshwater is important to understand the water security in the Himalayan region. While previous work has studied the western and central Himalayan glaciers, the eastern counterpart received less and more scattered attention. In this study, an attempt is made to quantify the total glacier-stored freshwater in the Brahmaputra basin and later compared with previous global models. Using open-source tools such as COSI-Corr and the Himalayan Glacier Thickness Mapper (HIGTHIM), the surface velocity and thickness of 1075 glaciers (> 1 km2) in the Brahmaputra basin were estimated, resulting in a current ice-volume estimate of 283 × 109 m3. Based on the laminar flow model, the mean ice volume ranges from 8284 to 230,186 m3, with an average of 36,570 m3. Sub-basin-wise evaluations of the total glacier-stored freshwater availability in the basin were also conducted, revealing that the Siang (89.998 × 109 m3, 31.45%) and Lohit (84.371 × 109 m3, 29.49%) sub-basins have significantly larger ice volumes than others. The average mean ice volume for each sub-basin are as follows: Teesta (45,233 m3), Sankosh (45,552 m3), Manas (39,581.7 m3), Subansiri (40,922.4 m3), Kameng (41,241.2 m3), Siang (36,120.5 m3), Dibang (31,792.2 m3), and Lohit (30,340.6 m3). Teesta, Sankosh, and Manas exhibit relatively higher average mean ice volumes than others. In comparison with the global studies, the present study's findings are acceptable with ensemble ice-volume estimates considering an uncertainty of ± 17.35%. Therefore, these results serve as a primary input for assessing the future changes in water resources and hazards related to water in the Brahmaputra basin.

"Mission-Aligned Funds Flow": Effect on Clinical Departments.

Academic medical centers struggle with the high cost of care, reduced reimbursement, intense competition, and low profit margins. Many factors, including a high proportion of publicly insured patients, a model rewarding procedural specialties, and research and educational support burden, led to faculty salary inequities, physician disengagement, and difficulty recruiting. UC Davis Health implemented an aligned funds flow model in July 2021 to create a mission-aligned model in which all departments had financial margins to optimize recruitment, retention, research, and teaching. The 3-year experience (academic years 2021-2024) with this model at UC Davis Health was characterized by physician compensation, physician recruitment, and profit increases. Total collections for departments increased by 4% in the first year, 0.2% in the second year, and 11.3% in the third year of funds flow. Total productivity increased by 4.9% during the first year, 3.6% during the second year, and 8.4% during the third year. Salaries increased in all departmental categories in year 3. Productivity and collections per faculty member increased during the first year and were stable during the second and third years. Parity among procedural, primary care, and hospital-based service lines was improved because departmental revenue was agnostic to payer mix and hospital agreements were more formulaic. The hospital contribution to funds flow increased from $67 million in 2022 to $101 million in 2024. Regular communication and transparency are critical to ongoing trust and success with implementation of sustaining funds flow. The new model resulted in improved physician compensation and increased hiring. However, the implementation of funds flow had a negative fiscal effect on the academic medical center, and sustainability may require fine-tuning to balance affordability. The authors plan to convert outpatient primary care to productivity-based models and decrease time-limited support for new faculty from 2 years to 1 year.

Thermal explosion and distribution of hydromagnetic Eyring–Prandtl double exothermic diffusion-reaction fluid in a porous channel

Harmful waste discharge poses a global threat to environmental degradation, as incomplete combustion of hydrocarbons can lead to unusual diseases and natural disasters, as well as toxic discharge. Therefore, this research aims to investigate the thermal explosion and distribution of hydromagnetic Eyring–Prandtl fluid during double exothermic combustion in a porous channel. The working Eyring–Prandtl fluid is assumed to be fully viscoelastic to inspire the combustion process in the absence of material deformation. A partial differential model of an electromagnetic pressure-driven flow is developed to govern the combustion reaction process in the presence of chemical kinetics, non-isothermal fixed wall constraints, and without fluid material reactant consumption. The model is transformed into an invariant form by introducing similarity variables; the resultant dynamical equations are solved via a finite difference semi-implicit scheme. The graphs and tables demonstrate that the rising parameter values for the double reaction step propelled heat transfer to help improve combustion processes. Also, the material dilatant parameter enhanced the fluid viscosity for increased chemical industrial usage which implies that, excessive heat generation due to exothermic combustion must be supervised to circumvent reactant species blowup. In addition, the magnetic field created complex dynamics in the fluid by introducing electromagnetic Lorentz forces, which changed the reaction rate and heat distribution inside the channel. Furthermore, there is a strong positive correlation between the results obtained in the current study and the existing published data.

Numerical Simulation of CBM Seepage Characteristics Based on Fracture Network Images

The natural fracture network within the coal body serves as the main pathway for gas migration, with its geometric characteristics significantly impacting coalbed methane flow. In order to enhance the numerical model for simulating coalbed methane flow based on fracture network images, we define porosity and permeability functions for these images and improve upon existing methods. By employing a pixel probability decomposition algorithm, we establish a geometric model of a rough discrete fracture network, which is imported into COMSOL Multiphysics to build a numerical model of gas flow. We analyze the impact of different fracture structures on coal seam permeability and find that gas primarily flows through interconnected fractures at much higher velocities compared to matrix pores. Furthermore, we observe that fracture network permeability increases with increasing porosity (0.0635–0.164), fractal dimension (1.571–1.755), maximum fracture branch length (0.0111–0.0249 m), and connectivity (0.808–2.789). Conversely, it decreases with an increasing fracture dip angle (1.61–88.39°) and tortuosity fractal dimension (1.0018–1.0195). Our simulation method based on fracture network imaging provides a simple yet feasible approach to simulate gas extraction while accurately capturing various stages in the extraction process, including the temporal and spatial evolution of gas velocity and pressure as well as differences between fractures and the coal matrix.

Upper convected Maxwell fluid in an isothermal flow with thermal radiation

In this research paper, a mathematical model of the isothermal flow of upper convected Maxwell (UCM) fluid with thermal radiation through a saturated porous media was studied in detail, with different physical parameters being considered. Maple 18 software is used to implement this strategy. The analysis of the results showed that the flow system was significantly influenced by the Schmidt, Darcy, and Deborah numbers, the unsteadiness parameter, the Maxwell parameter, the magnetic field parameter, and other physical characteristics. The influence of several physical characteristics on the flow system are discussed and shown graphically.

Recent Advances of PDMS In Vitro Biomodels for Flow Visualizations and Measurements: From Macro to Nanoscale Applications

Polydimethylsiloxane (PDMS) has become a popular material in microfluidic and macroscale in vitro models due to its elastomeric properties and versatility. PDMS-based biomodels are widely used in blood flow studies, offering a platform for improving flow models and validating numerical simulations. This review highlights recent advances in bioflow studies conducted using both PDMS microfluidic devices and macroscale biomodels, particularly in replicating physiological environments. PDMS microchannels are used in studies of blood cell deformation under confined conditions, demonstrating the potential to distinguish between healthy and diseased cells. PDMS also plays a critical role in fabricating arterial models from real medical images, including pathological conditions such as aneurysms. Cutting-edge applications, such as nanofluid hemodynamic studies and nanoparticle drug delivery in organ-on-a-chip platforms, represent the latest developments in PDMS research. In addition to these applications, this review critically discusses PDMS properties, fabrication methods, and its expanding role in micro- and nanoscale flow studies.

Selected social impact indicators influenced by materials for green energy technologies

The social risks of green energy transition are underexplored. One of the important questions is which materials used in green energy technologies offer the greatest social benefits, such as ensuring decent living conditions, and which pose the most social risks. To address this issue, we develop a dynamic material-energy flow model integrating system dynamics, social life cycle assessment, and geometallurgical approaches. The analysis focuses on critical materials: Rare Earth Elements, Nickel, Silicon, Graphite, Magnesium, Gallium, Germanium, Indium, Aluminum, Cobalt, Lithium, Zinc, and Tellurium used in wind turbines, electric vehicles, lithium-ion batteries and solar photovoltaic panels. We assess their social impact on work safety, gender equality, informal employment, labor income share, employment rate, and child labor—key issues addressed by Sustainable Development Goals 1, 5, and 8. Here we show that Aluminum production for electric vehicles, wind turbines and solar photovoltaic panels generates the most jobs and income opportunities, while extraction of Cobalt, Lithium, Silicon, and Zinc carry the highest social risks.

Magnetosheath Plasma Flow and Its Response to IMF and Geodipole Tilt as Obtained From the Data‐Based Modeling

AbstractLarge‐scale patterns of the steady‐state magnetosheath plasma flow and their dependence on the interplanetary magnetic field (IMF) have been reconstructed for the first time on the basis of large multi‐year multi‐mission pool of spacecraft observations, concurrent interplanetary data, and an empirical high‐resolution model. The flow model architecture builds upon a recently developed magnetosheath magnetic field representation by flexible expansions of its toroidal and poloidal components in a coordinate system, naturally conformed with the magnetopause and bow shock shapes. The model includes two physics‐based flow symmetry modes: the first one treats the magnetosphere as an axisymmetric unmagnetized obstacle, whereas the second mode takes into account the geodipole tilt, an important factor in the reconnection effects. The spacecraft data pool includes 1‐min average data by Themis (2007–2024), Cluster (2001–2022), and MMS‐1 (2015–2024) missions, as well as OMNI interplanetary data. The model drivers include the solar wind particle flux, IMF components, and the geodipole tilt angle. The model calculations faithfully reproduce the average plasma flow geometry and substantial effects have been found of the IMF orientation and magnitude, a principal factor that defines electromagnetic forces inside the magnetosheath. A strong dependence of the magnetosheath flow patterns on the Earth's dipole tilt indicates an important contribution of reconnection effects at the magnetopause to the solar wind particle transport around the dayside magnetosphere.