Search

In arid and semi-arid regions, groundwater is often the only available water source. However, overexploitation and pollution have led to a decrease in groundwater quantity and quality. Therefore, the proper management of groundwater resources is essential to promote sustainable development. Numerical simulation models (NSMs) have emerged as a valuable tool to address these challenges due to their ability to accurately and efficiently model groundwater systems. This study provides a comprehensive systematic review to evaluate the current knowledge on using numerical groundwater flow models for planning and water resource management in countries in the American region. A total of 166 research articles were published between the years 2000 and 2024. We analyzed and summarized details such as the study regions, numerical simulation methods and applied software, performance metrics, modeling units, modeling limitations, and prediction scenarios. In addition, we discuss alternatives to address the constraints and difficulties and suggest recommendations for future research. The continued research, improvement, and development of numerical groundwater models are essential to ensure the sustainability of groundwater resources. [ABSTRACT FROM AUTHOR]

Reliable predictions of the flow rate and viscous dissipation in the melt conveying zone of single‐screw extruders are crucial for designing high‐quality and efficient extrusion processes. Full‐scale computational fluid dynamics simulations offer deep insights into the process, but they cover only specific use cases. Conversely, state‐of‐the‐art analytical approximation models suffer from a systematic error by neglecting channel curvature. To overcome these limitations, we employed a hybrid modeling approach that efficiently combines analytical, numerical, and data‐based techniques. First, the mathematical problem was formulated for a three‐dimensional, isothermal Stokes flow of power‐law fluids in curved channel segments of unit length, and the theory of similarity was applied to render it in a dimensionless form. Using the finite‐volume method, the flow problem was then solved numerically for a wide range of extrusion setups. Finally, by means of symbolic regression and genetic programming, three dimensionless approximation equations were derived from the numerical dataset. These regression models provide continuous and remarkably accurate predictions of both flow rate and viscous dissipation rate, and clearly outperform existing approximations due to the included effects of channel curvature. Implemented within screw design software, our novel regression models will enable faster progress in screw design and process troubleshooting. Highlights: Three‐dimensional flow of power‐law fluids in helical screw channelsGeneralized problem description using dimensional analysisMelt conveying simulations considering both curvature and flight effectsIntegration of process knowledge into symbolic regression modelingAnalytical screw characteristic curves with extended scope of validity [ABSTRACT FROM AUTHOR]

This paper contains the results of numerical investigations into two cooling system types for cells of three types. The galvanic cell geometries which were considered were pouches, cylinders and prisms. By design, the cooling system for a vehicle is specialised to prevent an uncontrolled temperature increase at higher discharge rates. Consideration was given to the question of which cooling method would be sufficient to reduce the temperature rise of battery cells. The first cooling method investigated is one that uses direct contact with the air flow to cool the cells, a method that is very commonly used in automotive engineering, as it is less complicated. This study employs a method that uses a fan to induce forced convection, increasing the airflow over cells housed within a thermoplastic composite container. Another method, fluid cooling, is notable for its greater efficiency due to the use of a non-conducting coolant, which has also better energy absorption properties. In this study, immersion cooling was employed, utilising oil circulation through cells contained within a thermoplastic composite container, which was facilitated by a pump system. This publication shows the influence of the cell's geometry and the type of cooling system on the temperature rise of cells when they are discharging at the appropriate power rate. The results of this study highlight the differences in cooling performance between the two methods, providing a clear basis for selecting the most suitable solution for specific applications. [ABSTRACT FROM AUTHOR]

This study aims to establish a systematic approach for characterizing recycled polyolefins of unknown composition, with a specific focus on predicting their performance in film extrusion. We explore various characterization techniques, including differential scanning calorimetry (DSC), Fourier‐transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and rheometry to assess their effectiveness in identifying the polyethylene (PE) fractions within polypropylene (PP) recyclates. By integrating experimental data with modeling techniques, we aim to provide insights into the predictive capabilities of these techniques in determining processing behaviors. The research highlights the superior fidelity of DSC in predicting the relative fraction and type of PE in a PP recyclate. FTIR is also identified as a high‐fidelity approach, albeit requiring application‐specific calibration. TGA, capillary, and oscillatory rheometry are recognized for their ability to distinguish between grades of recycled polyolefins but provide aggregate behaviors rather than detailed constituent information. 3D flow simulation of the cast film extrusion investigated the effect of the viscosity characterization method, non‐isothermal assumption, and process settings but could not fully replicate the observed variations in the cast film processing of two industrial polyolefins with similar melt flow rates and viscosity behaviors. This underscores the practical challenge of predicting processing issues prior to actual processing, necessitating reliance on reliable instrumentation suites and human expertise for diagnosing and remedying variations. Highlights: Two industrial recycled polypropylene materials having similar melt flow rates exhibit drastically different cast film processing behaviors.DSC and FTIR provide reasonable approaches for identifying constituent materials.Modeling of the melt viscosities characterized by capillary and parallel plate rheology suggests that viscosity variations relative to the power‐law behavior assumed in the coat hanger die design is a predominant driver of cast film instabilities. [ABSTRACT FROM AUTHOR]

Monitoring and protecting flowing watercourses is a complex and challenging task that requires the collaboration and coordination of various stakeholders such as governments, industries, farmers, consumers and environmental groups. The study of the dynamics of the concentration of polluting factors and especially the concentrations of heavy metals and highlighting a seasonal variation is a necessary element from this point of view. In this article, we present the results of our analyses carried out in two measurement campaigns executed in 10 monitoring points along the Danube River, between Braila city and Isaccea city in the pre-deltaic area, during the summer season and autumn season 2022. The importance of this area is given by the fact that the Danube Delta is part of the UNESCO heritage, and the monitoring of polluting factors is a necessity in the desire to protect this area. The data measured during the July and August 2022 campaign cover a wide range of chemical species: Phosphate, CCO, CBO5, NH4+, N-NO2, N-NO3−, N-Total, P-PO4 3−, SO42−, Cl−, phenols, as well as metals with a harmful effect: Al, As, Cd, Cr, Fe. The study includes an evaluation based on the statistical approach of the results to highlight the significant correlations and differences identified between the two data sets. Next, to highlight the obtained results, a numerical model was considered using HEC-RAS and ESRI ArcGIS applications in a two-dimensional unsteady flow model in order to obtain the non-homogenous concentrations' distributions in the studied area. These two-dimensional models have been less studied in the specialized literature. In this way, interesting results could be obtained, and prediction methods regarding the dynamics of metal concentrations could be structured. The data obtained were used for the terrain model from the USGS service, and the flows of the Danube and its two tributaries were simulated using the data provided by the national services. In this work, we present the results obtained for the dynamics of the concentrations of the metals Al, As, Cd, Cr and Fe and the evaluation of the specific absorption coefficients for the explanation and correlation with the results of the measurements. Except for the numerical model presented, we would like to highlight the existence of some contributions of the main tributaries of the Danube in the study area. Such a systematic study has not been carried out due to conditions imposed by the border authorities. From this point of view, this study has an element of originality. The study is part of a more complex project in which the spatio-temporal distribution of the polluting factors in the water was evaluated, and the habitats in the study area were inventoried—especially those of community interest. In this way, we were able to expose the self-purification capacity of the Danube and highlight the existence of a concentration reduction gradient along the course of the river. The aspects related to the influence of the distribution of polluting factors on the state of health will be the subject of another article. [ABSTRACT FROM AUTHOR]

The dilute-foam dispersion system improves oil recovery by reducing interfacial tension between oil and water, altering wettability, and diverting displaced fluids by plugging larger pores. An optimized foaming system is obtained by formability evaluation experiments, in which the half-life for drainage and foaming volume by different types and concentrations of surfactants are analyzed, followed by the addition of partially hydrolyzed polyacrylamide (HPAM) with varied concentrations to enhance the foam stability. Using COMSOL Multiphysics 5.6 software, the Jamin effect and plugging mechanism of the water–gas dispersion system in narrow pore throats were simulated. This dispersion system is applied to assist CO2 huff-n-puff in a low-permeability core, combined with the online NMR method, to investigate its effects on enhanced oil recovery from the pore scale. Core-flooding experiments with double-pipe parallel cores are then performed to check the effect and mechanism of this dilute-foam dispersion system (DFDS) on enhanced oil recovery from the core scale. Results show that foam generated by combining 0.6% alpha-olefin sulfonate (AOS) foaming agent with 0.3% HPAM foam stabilizer exhibits the strongest foamability and the best foam stability. The recovery factor of the DFDS-assisted CO2 huff-n-puff method is improved by 6.13% over CO2 huff-n-puff, with smaller pores increased by 30.48%. After applying DFDS, the minimum pore radius for oil utilization is changed from 0.04 µm to 0.029 µm. The calculation method for the effective working distance of CO2 huff-n-puff for core samples is proposed in this study, and it is increased from 1.7 cm to 2.05 cm for the 5 cm long core by applying DFDS. Double-pipe parallel core-flooding experiments show that this dispersion system can increase the total recovery factor by 17.4%. The DFDS effectively blocks high-permeability layers, adjusts the liquid intake profile, and improves recovery efficiency in heterogeneous reservoirs. [ABSTRACT FROM AUTHOR]

Considering the importance of knowing and awareness of the watersheds water balance status, and analyzing the hydrological behavior of watersheds for planning and implementing water-related projects, the need to use new technologies in predicting water balance components is more evident than ever. Based on this, in the Kashkan basin by utilizing the TOPKAPI-X hydrological model, the water balance components of the basin were simulated according to the cellular network design. Digital maps of the basin, land use, outlet point, soil texture, elevation, and continuous time series of temperature, precipitation, and discharge in the daily time step are the main inputs of the model. The model in each cell network balances the water balance of the entire period. Model calibration was done for the 15 years of the statistical period (1999 to 2014) and model validation for the 6-year period (2014 to 2020). The results showed that 27.02 and 28.43 percent of the total precipitation of the Kashkan basin was discharged from the basin as total runoff (respectively for calibration and validation periods), which is consistent with the observation data at the outlet hydrometry station. Next, to evaluate the efficiency of the model, the simulated values in both statistical periods were compared to the observational discharge. Statistical methods such as the Nash-Sutcliffe evaluation criteria showed that the TOPKAPI-X model predicted the water balance components such as actual and potential evapotranspiration, infiltration, and the amount of runoff, especially the total runoff, in this basin with relatively good accuracy (coefficient above 60%). [ABSTRACT FROM AUTHOR]

For the purpose of efficient algae cultivation, the Photo Bio-Reactor (PBR) must be designed according to the needs of the algae to be cultivated. We performed our experiment with a loop reactor with a total volume of 14 liters. Among other things, the mixing of the gas and liquid phases, the value and change of the light intensity reaching the algae, and the degree of algae deposition on the walls of the equipment depend on the flow caused by the bubble column in the equipment. Using the ANSYS FLUENT simulation environment, we optimized the efficiency of the gas intake that determines the flow.

Floods are considered one of the most significant natural threats to cities and their infrastructure, especially when urban resilience is weak of floods, due to both human and natural factors. This is the case in the Algerian city of Tebessa, where urban resilience is low in the watershed of Wadi Nagues, which divides the city from north to south. Informal expansion along the riverbanks and inadequate city infrastructure increases the risk of flooding in the city. This study aims to identify the factors that increase flood hazards in Wadi Nagues and analyze maximum daily rainfall values to determine the maximum flood flow and volume during different return periods of 10, 50, 100, and 200 years, in order to map the floodplain of the river. This is accomplished using Geographic Information Systems (GIS) and HEC-RAS software for flood simulation. The results of the flood simulation in Wadi Nagues show that river waters inundate the southern areas of informal expansion, the airport, the railway, Houari Boumediene neighborhoods, and the Constantine Road – which is an economic artery for the city. The peak flow reaches 86.82 m³/h, and the volume of flow is 159.20 m³/s, in a during a 200-year return period. Field surveys also reveal several other human factors that increase the risk of flooding, such as informal expansion, lack and weakness of flood protection hydraulic structures, and poor river water cleanliness. This necessitates intervention to protect the city from flood hazard. [ABSTRACT FROM AUTHOR]

Liquid composite molding (LCM) is a common technology for manufacturing the polymer composites. The LCM process involves a non-isothermal flow of resin which influences the curing stage. The gradient of curing degree generated before gel point in curing stage seriously affects the quality of composites. The optimized design of cure cycle plays a crucial role in reducing gradient of curing degree. In this paper, the influence of non-isothermal flow on curing stage is considered. Based on ANSYS FLUENT software, the 3D non-isothermal resin filling-curing co-simulation is applied. The flow parameters, temperature parameters, and curing reaction parameters are fully considered in the co-simulation simulation, which can realize the multi-field coupling of thermal-flow-chemical field in the LCM process. The effectiveness of the co-simulation is verified by non-isothermal experiment of LCM process. An optimization method of cure cycle which the gradient of curing degree decreases significantly before the gel point is proposed. Through this method, the data obtained from the cyclic co-simulation to determine the temperature and heating rate at different curing times, and finally the optimal cure cycle, is obtained. Furthermore, these results have industrial significance for improving the LCM manufacturing of the key composite parts in aircraft, automobile, and ship technology. [ABSTRACT FROM AUTHOR]

Exploring the transport characteristics of leakage gas in the condenser can facilitate quicker identification of leak points when using Helium tracer gas method for detection. We construct a 3-D physical model of the condenser to simulate the Helium gas leakage process within the tube bundle. On the steam side, we adopt RNG k-e, porous media, steam condensation, and convective diffusion models to describe steam and leakage gas-flow. On the waterside, we use the tube bundle thermal resistance model to describe the steam-water heat transfer. The research concludes with three key points. When the centripetal pressure gradient is insufficient, there will be leakage gas enrichment, resulting in flowing out in the form of diffusion. When there is no centripetal pressure gradient in the tube bundle region, it will extract only a small amount of upstream leakage gas along with steam through the flow. When reaching a stable level for leakage gas, the leakage intensity is proportional to the outlets' flow rate but is independent of the transport form. The deviation of the mass-flow rate decreases with the mesh quantity increasing, which is less than 2% when the mesh quantity is over 638228. The deviation between simulated and actual values of the two parameters is less than 5%, which reveals the good agreement between numerical calculation and actual work conditions. These conclusions can assist employees and researchers in evaluating data on leak points and enhancing detection techniques. [ABSTRACT FROM AUTHOR]

The concepts of digital twins (DTs) have been widely studied to predict system performance, shorten design cycles, and implement preventive maintenance, but mainly, in large-scale enterprises. It is extremely beneficial to the whole manufacturing sector, since DTs can be readily implemented in small and medium-sized enterprises (SMEs) with basic computer aided engineering (CAE) tools; over 95% enterprises are SMEs. This paper aims to prove the feasibility of using commercial CAE tools, such as SolidWorks Simulation, to design air-quenching processes for SMEs. SMEs can benefit to explore new business opportunities, reduce system design cycle, and improve existing air-quenching processes. To our knowledge, it will be the first work of adopting DTs in conceptual design of an air-quenching process in sense that (1) the need of simulating an air-quenching process before physical implementation is discussed thoroughly; (2) heat transfer processes are classified, governing mathematical models for various heat transfer behaviors are introduced to present an evaluation model of a heat transfer process; (3) main process variables of air-quenching are identified; (4) a DT of an air-quenching process is developed and simulated to verify the capabilities of commercial SolidWorks Simulation; (5) case studies are developed to show how a CAE tool can be used in DTs. The findings from the reported work are summarized with a debrief of our future work. [ABSTRACT FROM AUTHOR]

While there are multiple methods to ventilate protective clothing, there is still room for improvement. In our research, we are using ventilation elements that are positioned at the ventilation holes in the air space between the body and clothing. These ventilation elements allow air to flow freely while preventing sun radiation, rain drops, and insects from directly accessing the body. Therefore, the shape of the ventilation element is crucial. This led us to study the shape optimization of ventilation elements through the utilization of metamodels and numerical approaches. In order to accomplish the objective, it is crucial to thoroughly evaluate and choose suitable criteria for the optimization process. We know from prior research that the toroidal cut-out shape element provides better results. In a previous study, we optimized the shape of this element based on the minimum pressure difference as a criterion. In this study, we are using different criteria for the shape optimization of ventilation elements to determine which are most effective. This study involves a metamodeling strategy that utilizes local and global approximations with different order polynomials, as well as Kriging approximations, for the purpose of optimizing the geometry of ventilation elements. The goal was achieved by a sequential process. (1) Planning the position of control points of Non-Uniform Rational B-Splines (NURBS) in order to generate elements with a smooth shape. (2) Constructing geometric CAD models based on the design of experiments. (3) Compute detailed model solutions using SolidWorks Flow Simulation. (4) Developing metamodels for responses using computer experiments. (5) Optimization of element shape using metamodels. The procedure is repeated for six criteria, and subsequently, the results are compared to determine the most efficient criteria for optimizing the design of the ventilation element. [ABSTRACT FROM AUTHOR]

Gravity assistance is a critical factor influencing CO2--eoil mixing and miscible flow during EOR and CO2 geological storage. Based on the NaviereStokes equation, component mass conservation equation, and fluid propertyecomposition relationship, a mathematical model for pore-scale CO2 injection in oilsaturated porous media was developed in this study. The model can reflect the effects of gravity assistance, component diffusion, fluid density variation, and velocity change on EOR and CO2 storage. For nonhomogeneous porous media, the gravity influence and large density difference help to minimize the velocity difference between the main flow path and the surrounding area, thus improving the oil recovery and CO2 storage. Large CO2 injection angles and oil--CO2 density differences can increase the oil recovery by 22.6% and 4.2%, respectively, and increase CO2 storage by 37.9% and 4.7%, respectively. Component diffusion facilitates the transportation of the oil components from the low-velocity region to the main flow path, thereby reducing the oil/CO2 concentration difference within the porous media. Component diffusion can increase oil recovery and CO2 storage by 5.7% and 6.9%, respectively. In addition, combined with the component diffusion, a low CO2 injection rate creates a more uniform spatial distribution of the oil/CO2 component, resulting in increases of 9.5% oil recovery and 15.7% CO2 storage, respectively. This study provides theoretical support for improving the geological CO2 storage and EOR processes. [ABSTRACT FROM AUTHOR]

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents part of the research on avoiding or reducing the surging effects that appear in the axial compressor intake manifold of a gas turbine. This research has led to an original solution validated by numerical simulations and experimental investigations. The increased amount of air suddenly required in the transient regime of the gas turbine is introduced into the intake manifold through slits arranged perpendicular to the direction of flow, on an aerodynamic profile at a certain angle to it and a certain distance from the minimum transversal section. The slits are arranged on the opposite sides of the gallery and connect with a transverse channel of the airfoil, in which there is air under pressure, from which the introduction of additional air is ordered. The numerical and experimental results extended to the influence of many geometric and mechanical parameters, proving that the proposed solution is as effective as possible compared to the classic ejector solution. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an emerging water treatment method that shows great promise for efficient desalination purposes. It enables the production of purified, potable water by effectively removing ions from seawater and brackish water. In this study, a unique capacitive deionization (CDI) cell design with an expansion part and without a spacer was proposed. It was then optimized using computational fluid dynamics (CFD) with ANSYS 21 (academic version) software to ensure a uniform flow distribution across the electrode surface, thus maximizing the utilization of the electrode. Subsequently, the developed optimum CDI cell was fabricated using 3D printing, and its desalination performance was evaluated in a batch system using NaCl solution. The optimum CDI cell design enhanced the salt adsorption capacity of the process by 47% compared to the first proposed design. The effect of operating parameters like potential, flow rate, and time on the salt adsorption capacity were investigated with the optimum CDI cell design. The maximum salt adsorption capacities were approximately 2.9 mg/g, 6.0 mg/g, and 14.7 mg/g for 2 mM, 20 mM, and 200 mM NaCl concentrations, respectively, at a potential of 1.2 V, a flow rate of 20 mL/min, and an adsorption/desorption period of 15 min. The electrodes exhibited a stable performance and full regeneration over long adsorption/desorption cycles. The findings of this study highlight the effectiveness of the proposed CDI cell design in enhancing salt removal efficiency. These results contribute to the advancement of water treatment technologies by providing insights into optimizing CDI processes for more efficient and sustainable desalination operations. [ABSTRACT FROM AUTHOR]

In arid and semi-arid regions, groundwater is often the only available water source. However, overexploitation and pollution have led to a decrease in groundwater quantity and quality. Therefore, the proper management of groundwater resources is essential to promote sustainable development. Numerical simulation models (NSMs) have emerged as a valuable tool to address these challenges due to their ability to accurately and efficiently model groundwater systems. This study provides a comprehensive systematic review to evaluate the current knowledge on using numerical groundwater flow models for planning and water resource management in countries in the American region. A total of 166 research articles were published between the years 2000 and 2024. We analyzed and summarized details such as the study regions, numerical simulation methods and applied software, performance metrics, modeling units, modeling limitations, and prediction scenarios. In addition, we discuss alternatives to address the constraints and difficulties and suggest recommendations for future research. The continued research, improvement, and development of numerical groundwater models are essential to ensure the sustainability of groundwater resources.

This paper contains the results of numerical investigations into two cooling system types for cells of three types. The galvanic cell geometries which were considered were pouches, cylinders and prisms. By design, the cooling system for a vehicle is specialised to prevent an uncontrolled temperature increase at higher discharge rates. Consideration was given to the question of which cooling method would be sufficient to reduce the temperature rise of battery cells. The first cooling method investigated is one that uses direct contact with the air flow to cool the cells, a method that is very commonly used in automotive engineering, as it is less complicated. This study employs a method that uses a fan to induce forced convection, increasing the airflow over cells housed within a thermoplastic composite container. Another method, fluid cooling, is notable for its greater efficiency due to the use of a non-conducting coolant, which has also better energy absorption properties. In this study, immersion cooling was employed, utilising oil circulation through cells contained within a thermoplastic composite container, which was facilitated by a pump system. This publication shows the influence of the cell’s geometry and the type of cooling system on the temperature rise of cells when they are discharging at the appropriate power rate. The results of this study highlight the differences in cooling performance between the two methods, providing a clear basis for selecting the most suitable solution for specific applications.

Deep reinforcement learning (DRL) is gaining attention as a machine learning tool for effective active control strategy development. This study focuses on employing DRL to develop an efficient active control strategy for flow around three circular cylinders arranged in an equilateral-triangular configuration in a two-dimensional channel. The analysis of control outcomes reveals that DRL induces vortices of varying sizes between the cylinders, resulting in large elliptical vortices at the rear. This enhancement in flow stability leads to a significant 40.40% reduction in cylinder drag force and an approximate 8.23% decrease in overall drag oscillations. Our research represents a pioneering application of DRL for stabilizing complex flow around multiple cylinders, yielding remarkable control effectiveness. The noteworthy outcomes in controlling the stability of complex flows highlight the capability of DRL to grasp intricate nonlinear flow dynamics, showcasing its potential for investigating active control strategies within complex nonlinear systems. [Display omitted] • Demonstrating deep reinforcement learning in non-linear, complex flow problems. • Remarkable 40.40% drag reduction, 8.23% less overall drag fluctuations. • Efficient implementation of real-time, multi-point active control for complex flow. [ABSTRACT FROM AUTHOR]

Knowledge of fracture properties and associated flow processes is important for geoscience applications such as nuclear waste disposal, geothermal energy and hydrocarbons. An important tool established in recent years are hydro-mechanical models which provide a useful alternative to experimental methods determining single fracture parameters such as hydraulic aperture. A crucial issue for meaningful numerical modeling is precise imaging of the fracture surfaces to capture geometrical information. Hence, we apply and compare three distinct fracture surface imaging methods: (1) handheld laser scanner (HLS), (2) mounted laser scanner (MLS) and (3) Structure from Motion (SfM) to a bedding plane fracture of sandstone. The imaging reveals that the resolution of the fracture surface obtained from handheld laser scanner (HLS) is insufficient for any numerical simulations, which was therefore rejected. The remaining surfaces are subsequently matched and the resulting fracture dataset is used for detailed fracture flow simulations. The resulting hydraulic aperture is calibrated with laboratory measurements using a handheld air permeameter. The air permeameter data provide a hydraulic aperture of 81 ± 1 µm. For calibration, mechanical aperture fields are calculated using stepwise increasing contact areas up to 15%. At 5% contact area, the average hydraulic aperture obtained by MLS (85 µm) is close to the measurement. For SfM, the measurements are fitted at 7% contact area (83 µm). The flow simulations reveal preferential flow through major channels that are structurally and geometrically predefined. Thus, this study illustrates that resolution and accuracy of the imaging device strongly affect the quality of fluid flow simulations and that SfM provides a promising low-cost method for fracture imaging on cores or even outcrops. Highlights: We evaluate a handheld laser scanner, a mounted laser scanner and the Structure from Motion method for imaging of fracture surfaces. We use the scanned geometries for flow simulations and calibrate the results with air permeameter measurements. Our study reveals that the handheld laser scanner is unsuitable for fracture surface imaging due to low resolution and accuracy. The simulations performed with geometries obtained by the mounted laser scanner and the Structure from Motion method provided comparable results. The Structure from Motion method seems to be promising for fracture investigations in field applications due to the high flexibility and low costs. [ABSTRACT FROM AUTHOR]

Based on the tortuous capillary network model, the relationship between anisotropic permeability and rock normal strain, namely the anisotropic dynamic permeability model (ADPM), was derived and established. The model was verified using pore-scale flow simulation. The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed. In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs, the effect of effective surface porosity on the permeability in all directions is consistent. With the decrease of effective surface porosity, the sensitivity of permeability to strain increases. The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity, while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity. For layered reservoirs with the same initial tortuosity in all directions, the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop. When the tortuosity is less than 1.6, the decrease rate of horizontal permeability is higher than that of vertical permeability, while the opposite is true when the tortuosity is greater than 1.6. This phenomenon cannot be represented by traditional dynamic permeability model. After the verification by experimental data of pore-scale simulation, the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions. [ABSTRACT FROM AUTHOR]

During the production of fiber-reinforced plastics using resin transfer molding (RTM), various characteristic defects and flaws can occur, such as fiber displacement and fiber waviness. Particularly in high-pressure RTM (HP-RTM), fiber misalignments are generated during infiltration by local peaks in the flow rate, leading to a significant reduction in the mechanical properties. To minimize or avoid this effect, the manufacturing process must be well controlled. Simulative approaches allow for a basic design of the mold filling process; however, due to the high number of influencing variables, the real behavior cannot be exactly reproduced. The focus of this work is on flow front monitoring in an HP-RTM mold using phased array ultrasonic testing. By using an established non-destructive testing instrument, the effort required for integration into the manufacturing process can be significantly reduced. For this purpose, investigations were carried out during the production of test specimens composed of glass fiber-reinforced polyurethane resin. Specifically, a phased array ultrasonic probe was used to record individual line scans over the form filling time. Taking into account the specifications of the probe used in these experiments, an area of 48.45 mm was inspected with a spatial resolution of 0.85 mm derived from the pitch. Due to the aperture that had to be applied to improve the signal-to-noise ratio, an averaging of the measured values similar to a moving average over a window of 6.8 mm had to be considered. By varying the orientation of the phased array probe and therefore the orientation of the line scans, it is possible to determine the local flow velocities of the matrix system during mold filling. Furthermore, process simulation studies with locally varying fiber volume contents were carried out. Despite the locally limited measuring range of the monitoring method presented, conclusions about the global flow behavior in a large mold can be drawn by comparing the experimentally determined results with the process simulation studies. The agreement between the measurement and simulation was thus improved by around 70%. [ABSTRACT FROM AUTHOR]

The squeeze‐film damping (SQFD) is an important dissipation mechanism of Micro‐Electro‐Mechanical Systems resonators. The current SQFD models of perforated plates treat borders of plate and holes as the constant pressure boundary, without considering border effect. In this paper, the border effect on SQFD is studied by expanding simulation area. At the same time, based on the research of non‐perforated plate border effect, the calculation size of the perforated plate hole cell is modified, and the modified SQFD model of the perforated plate has been built. Compared with simulation results, it shows the border effect has a great influence on SQFD of perforated plate. The precision of the modified model is higher than that of recent models. For a rectangular plate, the maximum error of the modified model is 12%, while for the recent model it is 40%. For a circular plate, the modified model is 38%, while the recent model is 58%. [ABSTRACT FROM AUTHOR]

This study proposes a novel approach for the wall-boundary immersed flow simulation, wherein the Navier-Stokes equation is modified to include a level-set definition of a solid body in fluid flow by an approach of viscosity solution of thickened interface. Following to the previous work for slip wall condition (Oshima, 2023a), a model of wall shear stress on no-slip condition is additionally proposed. One-, Two- and Three-dimensional simulations validate accuracy and applicability of wall model for theoretical and practical application.

Abstract Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining industries. However, accurately simulating the fluid flow in realistic fracture networks (compared to the statistical fracture networks) is still challenging due to the fracture complexity and computational burden. This work proposes a simple yet efficient numerical framework for the flow simulation in fractured porous media obtained by 3D high-resolution images, aiming at both computational accuracy and efficiency. The fractured rock with complex fracture geometries is numerically constructed with a cell-based discrete fracture-matrix model (DFM) having implicit fracture apertures. The flow in the complex fractured porous media (including matrix flow, fracture flow, as well as exchange flow) is simulated with a pipe-based cell-centered finite volume method. The performance of this model is validated against analytical/numerical solutions. Then a lab-scale true triaxial hydraulically fractured shale sample is reconstructed, and the fluid flow in this realistic fracture network is simulated. Results suggest that the proposed method achieves a good balance between computational efficiency and accuracy. The complex fracture networks control the fluid flow process, and the opened natural fractures behave as primary fluid pathways. Heterogeneous and anisotropic features of fluid flow are well captured with the present model.

The dilute-foam dispersion system improves oil recovery by reducing interfacial tension between oil and water, altering wettability, and diverting displaced fluids by plugging larger pores. An optimized foaming system is obtained by formability evaluation experiments, in which the half-life for drainage and foaming volume by different types and concentrations of surfactants are analyzed, followed by the addition of partially hydrolyzed polyacrylamide (HPAM) with varied concentrations to enhance the foam stability. Using COMSOL Multiphysics 5.6 software, the Jamin effect and plugging mechanism of the water–gas dispersion system in narrow pore throats were simulated. This dispersion system is applied to assist CO2 huff-n-puff in a low-permeability core, combined with the online NMR method, to investigate its effects on enhanced oil recovery from the pore scale. Core-flooding experiments with double-pipe parallel cores are then performed to check the effect and mechanism of this dilute-foam dispersion system (DFDS) on enhanced oil recovery from the core scale. Results show that foam generated by combining 0.6% alpha-olefin sulfonate (AOS) foaming agent with 0.3% HPAM foam stabilizer exhibits the strongest foamability and the best foam stability. The recovery factor of the DFDS-assisted CO2 huff-n-puff method is improved by 6.13% over CO2 huff-n-puff, with smaller pores increased by 30.48%. After applying DFDS, the minimum pore radius for oil utilization is changed from 0.04 µm to 0.029 µm. The calculation method for the effective working distance of CO2 huff-n-puff for core samples is proposed in this study, and it is increased from 1.7 cm to 2.05 cm for the 5 cm long core by applying DFDS. Double-pipe parallel core-flooding experiments show that this dispersion system can increase the total recovery factor by 17.4%. The DFDS effectively blocks high-permeability layers, adjusts the liquid intake profile, and improves recovery efficiency in heterogeneous reservoirs.

Abstract The squeeze‐film damping (SQFD) is an important dissipation mechanism of Micro‐Electro‐Mechanical Systems resonators. The current SQFD models of perforated plates treat borders of plate and holes as the constant pressure boundary, without considering border effect. In this paper, the border effect on SQFD is studied by expanding simulation area. At the same time, based on the research of non‐perforated plate border effect, the calculation size of the perforated plate hole cell is modified, and the modified SQFD model of the perforated plate has been built. Compared with simulation results, it shows the border effect has a great influence on SQFD of perforated plate. The precision of the modified model is higher than that of recent models. For a rectangular plate, the maximum error of the modified model is 12%, while for the recent model it is 40%. For a circular plate, the modified model is 38%, while the recent model is 58%.

Ecosystems in deep lakes are vulnerable to mixing regime alterations induced by global warming. Detection of mixing regime shifts contributes to a better understanding of the changes that occur in lake ecosystems due to climate change. In the winter of 2018/2019, the monomictic mixing in Lake Biwa, Japan, was partially incomplete. To identify the determining factor, our study reproduced this interruption in monomictic mixing using a realistic three-dimensional lake circulation model and heat budget analysis. The results revealed that weak surface cooling was primarily caused by a decrease in wind speed during the winter rather than by an increase in the air/water temperature, leading to the weak overturn and interruption in monomictic mixing. The results outlined that the mixing regime in Lake Biwa may be shifting from a monomictic to an oligomictic system because of atmospheric stilling or wind speed reductions affected by global warming. [ABSTRACT FROM AUTHOR]

Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining industries. However, accurately simulating the fluid flow in realistic fracture networks (compared to the statistical fracture networks) is still challenging due to the fracture complexity and computational burden. This work proposes a simple yet efficient numerical framework for the flow simulation in fractured porous media obtained by 3D high-resolution images, aiming at both computational accuracy and efficiency. The fractured rock with complex fracture geometries is numerically constructed with a cell-based discrete fracture-matrix model (DFM) having implicit fracture apertures. The flow in the complex fractured porous media (including matrix flow, fracture flow, as well as exchange flow) is simulated with a pipe-based cell-centered finite volume method. The performance of this model is validated against analytical/numerical solutions. Then a lab-scale true triaxial hydraulically fractured shale sample is reconstructed, and the fluid flow in this realistic fracture network is simulated. Results suggest that the proposed method achieves a good balance between computational efficiency and accuracy. The complex fracture networks control the fluid flow process, and the opened natural fractures behave as primary fluid pathways. Heterogeneous and anisotropic features of fluid flow are well captured with the present model. Highlights: Simple yet efficient method for fluid flow simulation in digital fracture network Fracture representation using a cell-based DFM with implicit fracture aperture A pipe-based cell-centered finite volume method for fluid seepage simulation Achieve a good balance between computational efficiency and accuracy Capture heterogeneous and anisotropic fluid flow characteristics [ABSTRACT FROM AUTHOR]

In micro-electrical discharge machining (micro-EDM) using the non-hollow circular cross-section tool electrode with the side flushing technique, when the aspect ratio of machined micro-hole is expected to be further increased, the discharge debris expelling speed and the working fluid renewal efficiency are weakened, which hinders the improvement of machining efficiency and accuracy with increased machining depth. In order to reveal the flow behavior of the working fluid in the micro-EDM gap, so as to realize the high-precision and high-efficiency machining of micro-hole with high aspect ratio, a three-phase flow simulation model of fluid, bubble, and debris is established in Fluent under the ideal assumption that the spark discharges occur continuously to generate high-pressure bubbles. The simulation results show that when the boundary condition of the flushing pressure at the side gap entrance is set to 0, the pressure wave emitted when the high-pressure bubble expands, which is formed by the instantaneous gasification of the working fluid between electrodes under high temperature, is the source of pneumatic force that drives the working fluid flow at the micron scale. Affected by the gap flow channel structure and the viscous resistance from inner wall, the flow velocity direction of the fluid dragging the discharge debris to rise up and expel will change, forming a dynamic alternation process of flowing into and out of the side machining gap entry. As the machining depth increases, due to the energy attenuation of the pressure wave propagating from the bottom gap to the side gap entrance, the expelling speed of the discharge debris decreases exponentially at the side gap entrance, resulting in the reduced machining efficiency and accuracy. However, when the simulated bubble generation frequency is increased to the megahertz level, the expelling efficiency of debris has a step-like improvement. The continuous and high-frequency generation of high-pressure bubbles can maintain a high pressure gradient in the bottom gap, and the discharge debris is able to continuously move upward without falling back to accumulate in the bottom gap, which is beneficial to the stable and smooth machining process, realizing the high-precision and high-efficiency machining of micro-hole with high aspect ratio. [ABSTRACT FROM AUTHOR]

X-ray computed tomography was applied in imaging 3D-printed gyroids used for bioseparation in order to visualize and characterize structures from the entire geometry down to individual nanopores. Methacrylate prints were fabricated with feature sizes of 500 µm, 300 µm, and 200 µm, with the material phase exhibiting a porous substructure in all cases. Two X-ray scanners achieved pixel sizes from 5 µm to 16 nm to produce digital representations of samples across multiple length scales as the basis for geometric analysis and flow simulation. At the gyroid scale, imaged samples were visually compared to the original computed-aided designs to analyze printing fidelity across all feature sizes. An individual 500 µm feature, part of the overall gyroid structure, was compared and overlaid between design and imaged volumes, identifying individual printed layers. Internal subvolumes of all feature sizes were segmented into material and void phases for permeable flow analysis. Small pieces of 3D-printed material were optimized for nanotomographic imaging at a pixel size of 63 nm, with all three gyroid samples exhibiting similar geometric characteristics when measured. An average porosity of 45% was obtained that was within the expected design range, and a tortuosity factor of 2.52 was measured. Applying a voidage network map enabled the size, location, and connectivity of pores to be identified, obtaining an average pore size of 793 nm. Using Avizo XLAB at a bulk diffusivity of 7.00 × 10−11 m2s−1 resulted in a simulated material diffusivity of 2.17 × 10−11 m2s−1 ± 0.16 × 10−11 m2s−1. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Beijing University of Civil Engineering & Architecture is the property of Journal of Beijing University of Civil Engineering & Architecture Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this article is to redesign centrifugal radial fans used in HVAC installations, using the analysis of aerodynamic flows and velocities distributions in the fan. Numerical simulations based on the reference model from the Pumps and Fans laboratory were performed using the Solid Works program, Flow Simulation module. Following the simulations, information regarding the fluid flow in the machine rotor and casing, the most suitable shape of the blades resulted, and redesign solutions through 3D printing technologies were proposed. Numerical simulations with Flow Simulation on three-dimensional models were carried out, for a better analysis of the volume of air passing through the fan, but also for the prediction of some negative effects: the appearance of vortices that lead to high noises/acoustic disturbances, the appearance of additional vibrations, but also sudden and uncontrolled variations in the pressure force. Following the numerical analysis, it was found that for the new blade profiles the velocities are uniform, which greatly reduces the noise and vibrations in the operation of the fan. The redesign also aims to reduce the energy consumption of these fans. [ABSTRACT FROM AUTHOR]

While there are multiple methods to ventilate protective clothing, there is still room for improvement. In our research, we are using ventilation elements that are positioned at the ventilation holes in the air space between the body and clothing. These ventilation elements allow air to flow freely while preventing sun radiation, rain drops, and insects from directly accessing the body. Therefore, the shape of the ventilation element is crucial. This led us to study the shape optimization of ventilation elements through the utilization of metamodels and numerical approaches. In order to accomplish the objective, it is crucial to thoroughly evaluate and choose suitable criteria for the optimization process. We know from prior research that the toroidal cut-out shape element provides better results. In a previous study, we optimized the shape of this element based on the minimum pressure difference as a criterion. In this study, we are using different criteria for the shape optimization of ventilation elements to determine which are most effective. This study involves a metamodeling strategy that utilizes local and global approximations with different order polynomials, as well as Kriging approximations, for the purpose of optimizing the geometry of ventilation elements. The goal was achieved by a sequential process. (1) Planning the position of control points of Non-Uniform Rational B-Splines (NURBS) in order to generate elements with a smooth shape. (2) Constructing geometric CAD models based on the design of experiments. (3) Compute detailed model solutions using SolidWorks Flow Simulation. (4) Developing metamodels for responses using computer experiments. (5) Optimization of element shape using metamodels. The procedure is repeated for six criteria, and subsequently, the results are compared to determine the most efficient criteria for optimizing the design of the ventilation element.

This study proposes a novel approach for the wall-boundary immersed flow simulation, wherein the Navier-Stokes equation is modified to include a level-set definition of a solid body in fluid flow. The proposed numerical model is defined via a system of differential equations based on the law of conservation and has a continuous approximate profile near the solid body. It yields a stable viscosity solution using a simple algorithm and scheme without any upwind schemes, numerical limiters, or addition filters. The model is numerically validated via solutions of flow around a cylinder, which are consistent with theoretical and experimental results for both steady and unsteady cases based on the wide Reynolds number (Re=8–160) of laminar flow condition.

Various stamp materials can significantly affect the filling quality of nanoimprint lithography (NIL). The effects of different stamp materials on the imprinting process were investigated from the angles of residual layer (RL) thickness, contact pressure, and filling proportion. The selection of various stamp materials affects the thickness and uniformity of the RL. Soft stamps (PDMS, PU) leave a thin but uneven RL distribution, while the RL imprinted by hard stamps (Si, Ni) is thicker but more uniform. The contact pressure using soft stamps is relatively more evenly distributed than hard stamps. The uneven distribution of contact pressure leads to poor cavity‐filling proportion, especially for hard stamps. This study offers guidance for choosing proper nanoimprint stamp materials for different NIL applications. [ABSTRACT FROM AUTHOR]

CO2 immiscible flooding is an environmentally-friendly and effective method to enhance oil recovery in ultra-low permeability reservoirs. A mathematical model of CO2 immiscible flooding was developed, considering the variation in crude oil viscosity and starting pressure gradient in ultra-low permeability reservoirs based on the non-Darcy percolation theory. The mathematical model and numerical simulator were developed in the C++ language to simulate the effects of fluid viscosity, starting pressure gradient, and other physical parameters on the distribution of the oil pressure field, oil saturation field, gas saturation field, oil viscosity field, and oil production. The results showed that the formation pressure and pressure propagation velocity in CO2 immiscible flooding were lower than the findings without considering the starting pressure gradient. The formation oil content saturation and the crude oil formation viscosity were higher after the consideration of the starting pressure gradient. The viscosity of crude oil considering the initiation pressure gradient during the formation was higher than that without this gradient, but the yield was lower than that condition. Our novel mathematical models helped the characterization of seepage resistance, revealed the influence of fluid property changes on seepage, improved the mathematical model of oil seepage in immiscible flooding processes, and guided the improvement of crude oil recovery in immiscible flooding processes. [ABSTRACT FROM AUTHOR]

The performance of a heat sink is significantly influenced by the type of cooling used: passive or active (forced), the shape of the heat sink, and the material from which it is made. This paper presents a review of the literature on the influence of geometry and surface parameters on effective heat transfer in heat sinks. The results of simulation studies for three different heat sink fin geometries and cooling types are presented. Furthermore, the influence of the surface texture of the heat sink fins on the heat transfer efficiency was determined. It was shown that the best performance in terms of geometries was that of a wave fin heat sink. When the surface texture was analyzed, it was found that an increase in the amplitude values of the texture decreases the heat dissipation efficiency in the case of active cooling, while for passive cooling, an increase in these parameters has a beneficial effect and increases the effective heat transfer to the surroundings. The cooling method was found to be the most important factor affecting heat dissipation efficiency. Forced airflow results in more efficient heat transfer from the heat sink fins to the surroundings. [ABSTRACT FROM AUTHOR]

Introduction and Objective : In recent years, river flow forecasting is one of the most important issues for water resources management in Iran. This prediction requires statistics and information, unfortunately, most of the basins of the country lack data of the desired quantity and quality. Material and Methods: Therefore, hydrological modelling and the use of artificial intelligence are examples of solutions that are used to solve this challenge in hydrology. The criteria for selecting the appropriate model for this process are to evaluate the performance of the models according to the hydrological conditions of each region. In this research, IHACRES model and Artificial Neural Network (ANN) were used to predict the streamflow in Bakhtiary basin. The data from 1984 to 1994 were used as calibration period and the data from 1995 to 2006 were used for validation. Results: The evaluation results of the hydrological model and the artificial neural network were evaluated using Kling -Gupta, Nash -Sutcliffe indices, coefficient of determination, mean squared error and absolute mean error. Results showed that the artificial neural network had better results in the simulation in all the evaluated evaluation criteria. Conclusion: According to the results of the methods used in the research, the artificial neural network method has a more accurate prediction of the Bakhtiary river flow than the hydrological model. [ABSTRACT FROM AUTHOR]

Copyright of Light Industry Machinery is the property of Light Industry Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)