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Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage 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.)

The electromagnetic stirring (EMS) and argon blowing are the widely recognized and extensively employed technologies to control the flow pattern in slab continuous casting, and their interaction is directly linked to the final product. To investigate the flow pattern, bubble characteristics under mold EMS and argon blowing, a mathematical model coupling the electromagnetic field, two‐phase flow is constructed. The population balance model (PBM) under the Eulerian frame is applied to describe the bubbles breakage and coalescence. The results show that the flow regime under the interaction of argon blowing and EMS transfers from bubble ascending flow to intermediate flow to horizontal recirculation flow as EMS current increases, and the large argon flow rate could suppress the formation of horizontal recirculation flow. Meanwhile, EMS can promote the coalescence of bubbles, with the increasing EMS current, the bubble numbers decrease first and then increase, and the bubble mean diameter increases first and then decreases. For obtaining the horizontal recirculation flow, the suitable argon flow rate and EMS current should be matched suitably. [ABSTRACT FROM AUTHOR]

Based on a diesel hydrogenation unit in Middle East, INPLANT software is for hydraulic calculations of the two-phase flow pipeline in the reaction system. The effects of pipeline diameter, gas-liquid ratio and fluid load on the transition of two-phase flow patterns in horizontal pipelines are analyzed. The results show that the unsteady slug flow can be transformed into stable annular flow by increasing the gas-liquid ratio of the fluid; changing the pipe diameter and fluid load cannot transform the two-phase flow pattern of the pipeline studied in this paper from slug flow to annular flow; however, when the liquid phase velocity is reduced to a sufficiently low, the flow pattern can be transformed into wavy flow. The calculation results are used to guide the operation adjustment of the unit, improving the gas-liquid ratio of the fluid can eliminate the pressure fluctuations of the reaction system. It shows that the flow pattern transformation trend simulated by the software is close to the actual production, and the accuracy is high. [ABSTRACT FROM AUTHOR]

This research analyses the flow patterns in an Oscillatory Central Baffled Reactor (OCBR) using Computational Fluid Dynamics (CFD) simulations under various oscillation conditions. Frequency (f and amplitude (x0) are examined as critical parameters for enhancing fluid mixing and energy efficiency in high viscosity fluids, such as biofuels. The findings highlight the significant impact of the Strouhal number (St) on the flow behavior, showing improved fluid mixing with an increase in the oscillatory Reynolds number (Re0) from 125.6 f = 2 Hz, x0 = 2 mm) to 392.7 f = 2.5 Hz, x0 = 5 mm), corresponding to a decrease in the St from 0.2 to 0.08. The simulations indicated the appearance of stable vortices and a better distribution of the Weibel dead zones at an oscillation cycle (t/T) of 0.5. During the course of the study, the pressure distribution within the OCBR and its dependence on oscillation amplitude were shown, which significantly impacted the pressure drop from 8.8 to 123 Pa as Re0 was raised. In order to alleviate the endpoints for high resistance of sharp edged baffles, two modified baffle designs (semi-central and smooth- edge central baffles) were used. The findings showed that the performance of the semi-central baffle design in terms of dead zone reduction and shear stress was superior to those of the other designs for both upward and downward flows, indicating its suitability for enhancing the performance of the OCBR. This research offers important developments in the efficient mixing processes needed in industrial applications and indicates some areas for effective testing and validation of the models developed. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter 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.)

Wall deposition is the main problem in a spray dryer that affects the quality of the powder and decreases the dryer operation. In the current study, the influence of using an air pressure nozzle on the conical section of the dryer chamber was examined by simulation of flow pattern in a pilot plant spray dryer using computational fluid dynamics (CFD) technique and Ansys Fluent software (Ver. 17.0). The governing equations are solved in an axisymmetric geometrical model meshed by quadratic elements. Flow pattern was studied and compared in two conditions: before and after considering air pressure nozzle in the dryer chamber wall. Verification of velocity magnitude revealed that there was a little difference (5% to 7%) between numerical and experimental values and there was a good correlation (R²≥ 95%) between them. Flow pattern in the dryer chamber in absence of wall pressure nozzle showed recirculation zones were formed at the end of cylinder part of the chamber. Considering wall pressure nozzle in the model caused deflection of inflow towards the dryer wall and extension of chamber central core flow. The simulation results showed deviation of particle deposition from cone section towards the cylinder and ceiling parts of dryer. [ABSTRACT FROM AUTHOR]

Modifying the PIVC tip to direct infusates toward areas of highest hemodilution may reduce vein wall damage. This study compared flow patterns between a traditional PIVC with a central opening and one with an off-axis aperture. Methods: This was an exploratory observational analysis conducted at a tertiary care emergency department (ED) comparing flow patterns of two intravenous catheters: PIVC 1 (2.95 cm 20 gauge [Autoguard, Becton Dickinson]) and PIVC 2 (3.68 cm 20 gauge [Osprey, SkyDance Vascular]). Adult ED patients with PIVCs placed via traditional palpation/visualization method and with ultrasound capturing the flushing were eligible participants. Ultrasounds were reviewed to determine vein, catheter, and flow characteristics. The primary outcome was angle of the infusate leaving the catheter. Secondary outcomes included direction of catheter tip against vein wall, distance away from vein wall, vasospasm, and laminar/turbulent flow. Results: Data from December 2023 included 28 catheters (10 PIVC 1, 18 PIVC 2). The average patient age was 53.7 years; 53.6% were female. Vein diameter/depth were similar: 0.35 cm/0.41 cm for PIVC 1 and 0.37 cm/0.47 cm for PIVC 2. The catheter tip pointed posteriorly towards the vein wall in 60% of PIVC 1 vs 11.1% in PIVC 2 (P=0.018). The angle of infusate flow away from the vein wall was 0.20° (SD 0.63) for PIVC 1 and 7.61° (SD 5.71) for PIVC 2 (P< 0.001). Flow at 0° occurred in 90% of PIVC 1 vs 16.7% in PIVC 2 (P< 0.001). Conclusion: In this exploratory investigation, a peripheral vascular access device with an off-axis tip aperture of demonstrated a sharper infusate flow angle away from the vein wall compared to a traditional central opening device. This redirection may reduce vein wall trauma and complications, though further research is needed to pair clinical outcomes with this technology. [ABSTRACT FROM AUTHOR]

The coupling between a transonic buffeting flow and a supercritical airfoil with harmonic heave motion was studied. A parametric space of the heave frequency and amplitude was investigated using a verified fluid–structural interaction framework. The spatial-temporal flow pattern around the transonic airfoil was studied using dynamic mode decomposition (DMD) to unveil the physical coupling mechanism. The results show three types of flow responses under the heave motion: (I) A buffet frequency response with a λ -shape shock wave structure and recirculation zone at the shock foot. The aerodynamic performance was alike the scenario in the flow past the stationary airfoil. (II) A transitional response with a weakened shock and enhanced boundary layer. The aerodynamic performance deteriorated sharply at f = f buffet and recovered after the frequency was past the buffet frequency. The flow pattern was characterized by a double-shock structure that interacted with the enhanced boundary layer. (III) A heave frequency response with the dominant heave motion. The variance in the aerodynamic loading increased significantly at f > f buffet and there were higher heave amplitudes in this stage. The driving motion of the airfoil transferred the energy of the buffet mode to the boundary layer with a more even energy balance according to the energy contribution analysis of the DMD modes. [ABSTRACT FROM AUTHOR]

【Objective】 The inlet forebay with a diffusion angle is a component of pump stations that helps distribute water flow evenly before it reaches the pump. We present a method in this paper to optimize the design of the inlet forebay, using the Xuliu Irrigation Station as a case study. 【Method】 The proposed method utilized the Navier-Stokes equations and the RNG k-ε turbulence model. Three-dimensional water flow in the forebay was numerically simulated under various scenarios, including the current configuration, modifications to the guide walls, and the addition of support columns. The optimal forebay design was determined by comparing the flow patterns generated in each scenario. 【Result】 Both guide walls and support columns improve flow patterns. Installing support columns increases the uniformity of average axial flow velocity distribution and the velocity-weighted average angle at the channel outlet to 97.74% and 88.42°, respectively, slightly surpassing the performance of the guide wall scheme and improving by 1.14% and 1.25° over the current configuration. At the channel inlet, the uniformity of average axial flow velocity distribution and velocity-weighted average angle were 62.86% and 65.82°, respectively, which were significantly higher than those achieved with the guide wall scheme and represented increases of 26.4% and 36.9° over the current configuration. The support column scheme also reduced the proportion of the vortex area in the forebay to 5%, compared to 7% with the guide wall scheme and 45% with the current configuration. 【Conclusion】 Installing support columns effectively improves the uniformity of water flow diffusion and reduces vortex areas, enhancing flow patterns in the forebay compared to the guide wall scheme. These results provide guidance for renovating the forebay at the Xuliu Irrigation Station and similar irrigation projects.

The penta-hybrid nanofluid is a nanofluid that contains five different types of nanoparticles. It can achieve higher heat transfer rates than conventional hybrid nanofluids due to the synergistic effects of the nanoparticles. It also has more diverse physical and thermal properties, which make it more adaptable for various applications. Therefore, this research examines the influence of localized magnetic fields on the vortex dynamics in a penta-hybrid nanofluidic flow in a vertical cavity with an aspect ratio of 1:10, driven by a top and bottom lid moving in the opposite direction. The stream-vorticity formulation is used to solve the dimensionless governing partial differential equation. A confined magnetic field in the form of horizontal and vertical strips has been applied instead of a uniform magnetic field throughout the flow domain, which is more realistic. Moreover, MATLAB codes developed by the authors are used to investigate how these parameters affect the flow and thermal properties of the nanofluids. The results suggest that magnetic fields have an impact on how stress, flow patterns, and temperature are distributed. Moreover, the presence of a magnetic field influences the spacing of isotherms, indicating a more even temperature distribution. It has also been observed that stress distribution is affected by the magnetic field, with higher stress levels near walls and regions with velocity-induced stress. However, in certain areas, the magnetic field can decrease shear stress depending on its strength and orientation. These study findings have implications for designing and operating nanofluidic devices. For instance, utilizing a magnetic field can help regulate flow patterns, temperature distribution, and stress distribution within nanofluidic channels. This capability could prove beneficial for a range of applications, such as cell separation, drug delivery, and nanofluidic heat exchange systems.

The study utilized computational fluid dynamics (CFD) simulations employing the volume of fluid (VOF) model to analyze silicone oil–air flows in a vertical pipe with a diameter of 67 mm. Various structured meshes ensured grid independence, and the k‐ε realizable model addressed turbulence. The analysis characterized bubbly to annular flows, involving the evaluation of flow patterns, radial void fractions, void fraction time series, probability density functions (PDFs), power spectral densities (PSDs), and mean void fractions. Results indicated a transition from bubbly to annular flow with increasing gas velocities and notable changes in radial void fraction profiles. Void fraction exhibited significant variations with distinct flow patterns at constant liquid velocity. PDFs identified flow regimes, and PSDs revealed frequency patterns. CFD results were validated against experiments, demonstrating good agreement. The validated CFD model was utilized to investigate radial gas velocities and pressure drops, revealing a shift from uniform velocity distributions to irregular patterns and a decrease in total pressure drop with an increase in gas superficial velocity. The model was also applied to a water‐air system to explore two‐phase flow behaviour. The impact of superficial gas velocity on flow patterns and radial void fractions was studied through numerical analysis and compared with the silicone oil‐air system. Results showed that at extreme gas velocities (0.06 and 5.53 m/s), silicone oil exhibited bubbly and annular flows, while water displayed cap bubbly and churn flows. The significant variation in radial void fraction at these velocities emphasized the impact of fluid properties. [ABSTRACT FROM AUTHOR]

A small leakage in the primary circuit of a nuclear power plant reactor may trigger the occurrence of countercurrent flow which probably develops into a flooding regime followed by the zero penetration caused core cooling failure. During extensive studies in the flooding phenomena in the PWR hot leg, the geometry effects have been widely investigated. The present study investigates the effects of I/D ratios of the riser on the interfacial fluctuations during the counter-current flow on a 1/30 scaled down PWR hot leg geometry. Here, the liquid film fluctuations were acquired by using parallel wire array probes on the basis of a conductance concept. Three I/D ratios which were varied consisted 1.9 (R1), 3.9 (R2) and 8.3 (R3). The obtained data were analyzed on the basis of both time and frequency domains. From the PDF the flooding regime obtains multimodal distributions, while the PSD approaches lower frequencies with higher magnitudes corresponding to either the occurrence of water blockage or slugs. Keywords: I/D ratio, water level fluctuation, counter-current flow, PWR hot leg, parallel wire array probe, stochastic analysis.

This research is aimed to investigate the accuracy and cost-effectiveness of numerical simulation method for the study of flow in a waterwheel system by comparing the results to the results of experiment, as well as by comparing the computational load of various solution schemes. The simulation is performed using Ansys Fluent with sliding mesh interface (SMI) method to treat the interface between rotating waterwheel region and static channel region. The governing equations are solved using the SIMPLE and Coupled schemes, and the effects of spatial and temporal resolutions are investigated. In general, the values of torque and power and the flow patterns obtained using numerical simulation are in a good agreement with those obtained using the experiment, which confirms the reliability of the simulation method. Considering the accuracy and computational load, it is recommended to use the Coupled scheme instead of the SIMPLE scheme for numerical simulation using SMI method.

Abstract Dissolved air flotation (DAF) is an effective method for separating suspended oil and solid particles from wastewater by utilizing small air bubbles. This study aims to investigate the impact of key factors, such as saturating pressure and water flow rate, on the separation of fine oil droplets from a water stream. The macroscopic flow patterns within the cell were analyzed using particle image velocimetry (PIV), while Digital Image Analysis (DIA) was employed to study microscopic phenomena, including oil droplet rising velocity and oil-bubble contact mechanisms. Our findings propose a safe operating window (specifically, water flow rate and saturation pressure) for the effective separation of oil droplets without any oil escaping into the clean water stream. It was found that the oil droplet rising velocity increases with the saturation pressure up to 200 kPa. However, a further increase in the pressure of the air saturating chamber leads to a decrease in oil droplet rising velocity. Additionally, we identified a peak in rising velocity at an oil droplet size of approximately 200 µm. Below this threshold, the rising velocity increases with droplet size, while for droplet sizes exceeding 200 µm, the rising velocity decreases with size. This behavior can be explained by the conflicting effects of droplet size increment according to the Stokes law for the rising velocity of oil droplets. As the droplet size increases, the average density of the bubbles/droplet aggregate rises, reducing the ∆ρ in the Stokes law and subsequently lowering the aggregate rising rate. However, as per the Stokes law, the oil droplet rising velocity increases proportionally to the square of its size.

The luminal surface of the endothelium is exposed to dynamic blood flow patterns that are known to affect endothelial cell phenotype. While many studies have documented the phenotypic changes by gene or protein expression, less is known about the role of blood flow pattern on the endothelial cell (EC) lipidome. In this study, shotgun lipidomics was conducted on human aortic ECs (HAECs) exposed to unidirectional laminar flow (UF), disturbed flow (DF), or static conditions for 48 h. A total of 520 individual lipid species from 17 lipid subclasses were detected. Total lipid abundance was significantly increased for HAECs exposed to DF compared to UF conditions. Despite the increase in the total lipid abundance, HAECs maintained equivalent composition of each lipid subclass (% of total lipid) under DF and UF. However, by lipid composition (% of total subclass), 28 lipid species were significantly altered between DF and UF. Complimentary RNA sequencing of HAECs exposed to UF or DF revealed changes in transcripts involved in lipid metabolism. Shotgun lipidomics was also performed on HAECs exposed to proinflammatory agonists lipopolysaccharide (LPS) or Pam3CSK4 (Pam3) for 48 h. Exposure to LPS or Pam3 reshaped the EC lipidome in both unique and overlapping ways. In conclusion, exposure to flow alters the EC lipidome and ECs undergo stimulus-specific lipid reprogramming in response to proinflammatory agonist exposure. Ultimately, this work provides a resource to profile the transcriptional and lipidomic changes that occur in response to applied flow that can be accessed by the vascular biology community to further dissect and extend our understanding of endothelial lipid biology. [ABSTRACT FROM AUTHOR]

The present study aims to examine the changing hydro-geomorphological properties of the Mayurakshi River located in a plateau fringe region in Jharkhand and West Bengal. The field investigation of 14 cross-sectional sites has been conducted during the post-monsoon season of 2021 to determine important geomorphic parameters such as channel depth, width, bank height, hydraulic radius, and wetted perimeter. Post-processed kinematic survey and electromagnetic current meter tool have been used to measure the river bed profile and channel velocity, respectively, to obtain more accurate locational information. The primary objective of this study is to compare field-observed discharge data with the discharge volume predicted by a few hydraulic and hydrological models in order to determine the models that are best suited for further application in a scientifically accepted and cost-effective manner. The results demonstrate that there is a noticeable rise in flow velocity from upstream (0.22 m/s) to downstream of the river (0.85 m/s), which is also supported by the results of Manning's equation and kinematic wave parameter. The most correct relationship is then presented by minimizing the deviations between the calculated and analytical discharges at three separate stages. The results show that the proposed Manning's technique is quite accurate with the observed data, as determined by the mean absolute percentage error (60.16%), root mean square error (30.53%), and normalized root mean square error (0.05) indices. [ABSTRACT FROM AUTHOR]

Lateral cavities are a popular object of study in hydraulic research as they are widely found in rivers and hydraulic facilities and significantly impact flow patterns, sediment transport, and water quality in aquatic ecosystems. While the effects of open-channel cavities on various aspects including characteristics of three-dimensional structures have been extensively studied, the role of vertical flow structures in the cavity has not been focused on. This study examines the relationship between the shallowness parameter and the three-dimensional flow effects on the dynamics of an open-channel lateral cavity flow with horizontal vortex motion, comparing the conventional two-dimensional model (2DC), advanced depth-integrated models including general bottom velocity calculation method (GBVC) with the ability to consider vertical flow structures, simplified bottom velocity calculation method with the shallow water assumption (SBVC), a three-dimensional model (3DC), and experimental data. The comparison results demonstrate that the three-dimensional flow effect significantly impacts the velocity distribution and vortex evolution in the cavity. The GBVC model demonstrates a good agreement with the flow patterns by the 3DC model and experimental results in the cavity, whereas the 2DC and SBVC models are unsuitable for deep-water conditions. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. 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.)

Proton exchange membrane fuel cells are a prime choice for substitute electricity producers. Membrane electrode assembly (MEA), bipolar electrodes, and current collectors belong to only a limited number of primary parts of the proton exchange membrane fuel cell (PEMFC). Bipolar plates are among the most famous elements in the fuel cell; they are responsible for the electrochemical reaction, as well as the flow of gases from one bipolar plate to another. A bipolar plate is to be a good electro-conducting, non-corrosive, and a high mechanical strength product. The attainability of the specification is achieved by graphite and metallic materials, each one having its own merits and demerits that are discussed in this article. Likewise, making the second pass for the flow pattern is equally important for the cell to have good performance and efficiency. The emergence of innovative and new bipolar plate designs has caused the achievement of high performance of these plates. The present review article principally focuses on the experimental study of diverse flow fields in the design of PEMFC and on the influence of various geometrical properties on the general operation of fuel cells made of PEMFC, and also on the manufacturing procedure utilized for building contemporary fuel cells. [ABSTRACT FROM AUTHOR]

In industrial production and water resource management involving fluid flows, two-phase flow measurement in complex environments has always been a research hotspot. In this study, a broadband detection device (40–110 MHz) suitable for two-phase flow in pipes was designed in a laboratory environment, the impedance response of two-phase flow was investigated under different salinity conditions and flow patterns, and a new impedance dispersion model suitable for two-phase flow in pipes was built. The experimental results show that the new model can better describe the rules of impedance dispersion in two-phase flow and is universally applicable, and that the equivalent solution resistance and interfacial polarization frequency have a stable functional relationship with water holdup. Based on the static experimental results, water holdup evaluation models for four flow patterns were established, and the dynamic detection results were predicted. The prediction results show that the new method proposed herein is not affected by changes in salinity and flow pattern when the flow pattern is known, and that its accuracy can meet the production requirements. This study expands the application range of traditional single-frequency conductivity detection techniques and provides a new idea for the development and improvement of systems for online detection of water holdup in two-phase flow. [ABSTRACT FROM AUTHOR]

Accurately and instantly estimating the hydrodynamic characteristics in two-phase liquid–gas flow is crucial for industries like oil, gas, and other multiphase flow sectors to reduce costs and emissions, boost efficiency, and enhance operational safety. This type of flow involves constant slippage between gas and liquid phases caused by a deformable interface, resulting in changes in gas volumetric fraction and the creation of structures known as flow patterns. Empirical and numerical methods used for prediction often result in significant inaccuracies during scale-up processes. Different methodologies based on artificial intelligence (AI) are currently being applied to predict hydrodynamic characteristics in two-phase liquid–gas flow, which was corroborated with the bibliometric analysis where AI techniques were found to have been applied in flow pattern recognition, volumetric fraction determination for each fluid, and pressure gradient estimation. The results revealed that a total of 178 keywords in 70 articles, 29 of which reached the threshold (machine learning, flow pattern, two-phase flow, artificial intelligence, and neural networks as the high predominance), were published mainly in Flow Measurement and Instrumentation. This journal has the highest number of published articles related to the studied topic, with nine articles. The most relevant author is Efteknari-Zadeh, E, from the Institute of Optics and Quantum Electronics. [ABSTRACT FROM AUTHOR]

River interaction is a problematic place in hydraulic engineering. This is rooted in creating an intricate behavior that leads to the development of vortex flow at the intersections and results in sediment deposition in these areas. This phenomenon depends on various factors, from flow rate ratio, intersection angle, channel geometry, longitudinal slope to bed resistance, and lateral channel width ratio to the main channel. Studying flow patterns is a necessary action that can assist in predicting the changes in bed morphology and preventing issues, such as main channel blockage while increasing the flow rate in the main channel. The SSIIM2.0 model's capacity to simulate three-dimensional flow at a confluence was used to examine the effects of bed morphology and flow parameters on junction angle, flow rate ratio, and lateral channel width ratio. With correlation values of 0.9 and 0.68 for velocity and bed profiles, the results show that this model can reasonably predict these variables. Additionally, the effect of various junction angles (45, 60, 75, 90, and 105 degrees) on hydraulic flow, particularly maximum bed shear stress, temporal variation of shear stress, and dimensions of the separation area, were examined. At the 45° angle, a significant separation area was not observed, but the results showed that with an increase in the junction angle, the dimensions of the separation area are increased. Dimensionless length of the separation zone has decreased by 18% due to a change in the connection angle from 60° to 105°. Meanwhile, the width of the separation zone has increased by 60%. Furthermore, the results indicate that increasing the tributary angle from 45° to 105° resulted in a 91.8% increase in maximum bed shear stress at the junction location. [ABSTRACT FROM AUTHOR]

Dissolved air flotation (DAF) is an effective method for separating suspended oil and solid particles from wastewater by utilizing small air bubbles. This study aims to investigate the impact of key factors, such as saturating pressure and water flow rate, on the separation of fine oil droplets from a water stream. The macroscopic flow patterns within the cell were analyzed using particle image velocimetry (PIV), while Digital Image Analysis (DIA) was employed to study microscopic phenomena, including oil droplet rising velocity and oil-bubble contact mechanisms. Our findings propose a safe operating window (specifically, water flow rate and saturation pressure) for the effective separation of oil droplets without any oil escaping into the clean water stream. It was found that the oil droplet rising velocity increases with the saturation pressure up to 200 kPa. However, a further increase in the pressure of the air saturating chamber leads to a decrease in oil droplet rising velocity. Additionally, we identified a peak in rising velocity at an oil droplet size of approximately 200 µm. Below this threshold, the rising velocity increases with droplet size, while for droplet sizes exceeding 200 µm, the rising velocity decreases with size. This behavior can be explained by the conflicting effects of droplet size increment according to the Stokes law for the rising velocity of oil droplets. As the droplet size increases, the average density of the bubbles/droplet aggregate rises, reducing the ∆ρ in the Stokes law and subsequently lowering the aggregate rising rate. However, as per the Stokes law, the oil droplet rising velocity increases proportionally to the square of its size. [ABSTRACT FROM AUTHOR]

• Flow boiling of R134a in a plate heat exchanger with wavy corrugations was studied. • Three major flow patterns were identified with the variation of vapor quality. • The variation of heat transfer coefficient and wall temperature were discussed. • A new piecewise Nu correlation was developed based on flow pattern transition. As a common component in various applications, the two-phase heat transfer of plate heat exchanger has been frequently studied. However, further investigations are still required on the flow pattern, especially for those with new plate structures brought with the emergence of new applications. This study presented an experimental investigation on the flow boiling of R134a in a plate heat exchanger with mini-wavy corrugations designed for thermal management system of electric vehicle (EV). The flow pattern transitions in the test section were captured and discussed, meanwhile the effects of vapor quality and mass flux on the variation of heat transfer coefficient (HTC) were analyzed. Based on the observation, the two-phase flow pattern developed from pulsating film flow, then rough stream flow and finally to thin stream flow with the increase of vapor quality. The flow pattern map was determined with the superficial momentum of the liquid and vapor phase refrigerant, while the empirical correlations were developed based on two-phase Weber number to predict the transitions between the flow patterns. The HTC showed an intermediate increase firstly under low vapor qualities, and rapidly decreased after reaching the peak value at the vapor quality of 0.45–0.6. In addition, the experimental data were compared with the present correlations, and a new Nu correlation was developed considering the transitions of flow patterns, showing an optimal prediction on the experimental data with the mean absolute error of 11.3%. [ABSTRACT FROM AUTHOR]

Many efforts have been dedicated to examining the flow characteristics around a pair of cylinders. Despite the straightforward geometry, the flow dynamics around a cylinder prove to be intricate. The practical applications of this phenomenon extend across various engineering domains, including oil and gas transmission lines, heat exchangers, pipelines, and the construction of successive skyscrapers. The current investigation delves into the examination of the critical distance ratio, fluctuating velocity, flow pattern, and drag surrounding two sequential circular and square cylinders. The governing equations are solved using the finite volume method (FVM). For momentum, turbulent kinetic energy, and turbulent dissipation rate equations, the upwind second-order discretization is used. The findings, acquired at a Reynolds number of 32,000 for distance ratios ranging from 0.25 to 10, are then compared with those from single-cylinder cases. The results highlight the significant influence of both geometry and the distance between cylinders on the observed flow patterns. The critical distance ratio is obtained as s c = 2 and 2.5 for the case of two sequential circular and square cylinders, respectively, while for the case of combined circular and square cylinders, it is calculated as s c = 3. The non-dimensional fluctuating velocity decreases by 7%, 26%, and 38% in the case of two sequential circular cylinders with distance ratios of S* = 1, 2, and 3 at the first station, respectively, compared to a single circular cylinder. The drag coefficient is 50% lower in the two sequential circular and square cylinders case compared to the single square cylinder. [ABSTRACT FROM AUTHOR]

Fluid production from unconsolidated reservoirs often leads in sand production, which poses a number of issues. Sand deposition in flowlines can result in significant pressure dips, pipe and facility damage, and obstructions that decrease productivity. More research is needed to understand the movement and deposition of sand in oil--water--sand (O--W--S) fluxes. This article focuses on O--W--S flows in a 6-meter-long horizontal pipe with an inner diameter of 0.0381 m. The study looks at the flow behavior of high viscosity oil-water (O--W), wateresand (W--S), and oil--water--sand (O--W--S) flows. Experiments were carried out at 250 psig pressure in a laboratory flow test facility using various heavy synthetic oils (viscosities ranging from 3500 cP to 7500 cP at 25°C) and tap water. The sand concentration varied from 1% to 10%, with an average sand particle diameter of 145 mm and material density of 2630 kg/m³. Water cuts ranged from 0.0 to 1.0. The experimental results revealed a minor change in pressure gradient between (O--W) and (O--W--S) flows. However, increasing the sand concentration in (O--W--S) flow resulted in higher pressure losses. The reduction factor of pressure gradient indicated that the highest decrease in pressure drop occurred at higher superficial oil velocities. Furthermore, a direct relationship was observed between the reduction factor and the decrease in water cut. The results also showed that the minimum required transportation velocity for sand slurry decreased with increasing superficial oil velocity, while the minimum transportation condition increased with higher sand concentration. The comparison between the expected pressure gradient from Bannwart and McKibben et al. and the actual experimental data demonstrated significant accuracy for the oil viscosities and superficial oil velocities used in the study. [ABSTRACT FROM AUTHOR]

This work presents an experimental study on oil–water flow downstream of a restriction. The flow pattern, volumetric phase distribution, and their impacts on pressure drop are discussed. We employed two techniques to visualize the oil–water flow patterns, a high-speed camera and an Electrical Capacitance Volume Tomography (ECVT) system. The ECVT system is a non-intrusive device that measures the volumetric phase distribution at the pipe cross-section with time, which plays a critical role in determining the continuous phase in the oil–water flow, and therefore the oil–water flow pattern. In this study, we delved into the oil–water flow pattern and volumetric phase distribution for different valve openings, flow rates, and water cuts, and how they impact the pressure drop. The experimental results have demonstrated a strong relationship between the oil–water flow pattern and the pressure gradient, while the oil–water flow pattern is significantly influenced by the flowing conditions and the valve openings. The impacts of water cuts on the oil–water flow pattern are more obvious for smaller valve openings. For large valve openings, the oil and water phases tend to be more separated. This results in a moderate variation in the pressure gradient as a function of water cuts. However, it becomes more complex as the valve opening decreases. The pressure gradient generally increases with decreasing valve openings until the flow pattern becomes an oil-in-water dispersed flow. The impact of the valve on the pressure gradient is more pronounced in water-dominated flow when the water cut is above the inversion point, while it seems to be most obvious for medium water cut conditions. [ABSTRACT FROM AUTHOR]

Abstract High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH3-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier.

Vortex-induced vibration (VIV) is characterized as a phenomenon of limited amplitude vibration. Understanding the basic nature and underlying mechanism of VIV is necessary for predicting the vibration amplitude. In this study, using Large Eddy Simulation (LES) of forced vibration, a detailed investigation of the flow pattern and wind load during VIV of a 4:1 rectangular cylinder is conducted. The results indicate that both vibration amplitude (y 0 /D) and wind speed (U R) significantly influence the flow pattern and wind load. Notably, an increase in vibration amplitude leads to a predominance of motion-induced force and a corresponding amplification of the fluctuating lift coefficient. Additionally, a decrease in the phase difference between lift force and displacement is observed, establishing this phase difference as a critical parameter for predicting vibration amplitude. Regarding wind speed, it is observed that as U R increases, the predominance of motion-induced force diminishes, resulting in a concurrent decrease in the fluctuating lift coefficient. Upon further investigation into the work performed by various forces within a single vibration cycle, it has been determined that as the vibration amplitude escalates, the work of the lift force (energy input W I) initially increases, then diminishes, whereas the work of the damping force (energy dissipation W O) continuously rises. The intersection of these two trajectories signifies the point of energy equilibrium between input and output, thereby establishing the vibration amplitude of VIV. The predicted vibration amplitudes, grounded in this principle, have been corroborated by experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the gas–liquid two-phase flow within a Tesla valve under zero-gravity conditions is numerically studied. Based on the VOF model and the inlet two-phase separation method, the forward and reverse flow patterns and pressure drop changes in a Tesla valve at different inlet velocities were analyzed. At an inlet velocity of 0.1–0.2 m/s, the flow pattern was slug flow, the bubbles were evenly distributed in different positions in the Tesla valve, and the velocity difference between the main pipe and the arc branch pipe was small. When the inlet velocity was 0.4 m/s, the main flow pattern was annular flow, and there was a phenomenon of gas–liquid phase separation through different flow channels, which was related to centrifugal force. At an inlet velocity of 0.6–0.8 m/s, bubbly flow and slug flow coexisted, which was related to the uneven velocity. In the study range, the difference in the forward and reverse pressure drops of two-phase flow was smaller than that of single-phase flow, and the two-phase diodicity decreased first and then increased with the change in inlet velocity, reaching minimum values of 0.78 at 0.2 m/s and 1.44 at 0.8 m/s. [ABSTRACT FROM AUTHOR]

The pre-engineering diversion project in narrow river valley with high water head, high discharge and complex geological conditions faces the issue of high speed water discharge, which requires higher energy dissipation body type. Based on hydraulic physics model test, the energy dissipation type at the outlet of diversion tunnel of a hydraulic project was optimized and explored, and four layout schemes including right bank orientation, tunnel line deviation, left bank diversion and forced energy dissipation + left bank diversion were proposed. Through the determination and comparison of hydraulic parameters such as water flow pattern, velocity and erosion characteristics, the compound energy dissipation type of forced energy dissipation + left bank diversion was finally recommended, and the adaptability of the recommended type to the large and small flow conditions was tested and analyzed throughout the diversion process. The test results show that the composite energy dissipation body type has higher energy dissipation efficiency under each working condition, the flow velocity of cofferdam and left bank near shore is obviously reduced, the dispersed water flow can effectively block backflow, the intensity of water surface fluctuation is weakened, the main flow returns to the channel smoothly, the scouring and siltation situation is good and the left bank is protected from scouring. The composite energy dissipation body type can meet the project energy dissipation, safety and stability requirements, and can provide reference for the outlet design of the diversion tunnel project with similar characteristics. [ABSTRACT FROM AUTHOR]

In this work, we employed laser speckle contrast imaging coupled with the analysis of several statistical moments on the recorded images to recognize the shape of an object through the analysis of the pattern of a flow around it. We postulated that a flow through different geometries would generate a unique flow structure and thus the mathematical analysis of the differences can be utilized to detect and recognize various shape geometries. To this aim, the flow of scattered liquid that had passed through objects of different shapes was illuminated by a laser beam and the diffused speckle image was recorded by a camera. In the computer, the captured speckle image was first converted to a flow image and then mathematically analyzed to recognize the shape of the objects. Three out of the eight statistical metrics were found to be the best candidates for the recognition of shapes, thus proving our hypothesis. [ABSTRACT FROM AUTHOR]

The article presents experimental results of boiling heat transfer during FC-770 flow in a group of five minichannels with a common heated wall. The flow orientation was changed from 0° to 180°, with a 15° increment. During the experiments, the temperature of its outer heated wall surface was measured by an infrared camera. At the same time, flow patterns were captured through the glass plate opposite the heated wall using a high-speed camera. The purpose of the calculations was to determine local heat transfer coefficients on the contact surface between the working fluid and the heated surface in the central minichannel, using a simplified 1D calculation method. The results in the form of dependences of the temperature of the heated wall and the heat transfer coefficient as a function of the distance from the channel inlet for various flow orientations were analysed. Furthermore, typical boiling curves and two-phase flow patterns were presented. The mean relative error of the heat transfer coefficient was determined for various flow orientation. The dependence of the void fraction as a function of heat flux was illustrated for various angles of minichannel inclination to the horizontal plane. It was observed that the void fraction increased with heat flux and with increasing angle of inclination of the minichannel to the horizontal plane. [ABSTRACT FROM AUTHOR]

The optimization design of the double-layered material tank is essential to improve the material mixing efficiency and quality in chemical engineering and lithium battery production. The draft tube structure and double-layered impellers affect the flow patterns of the fluid–solid transfer process, and its flow pattern recognition faces significant challenges. This paper presents a fluid–solid mixing transfer modeling method using the CFD-DEM coupling solution method to analyze flow pattern evolution regularities. A porous-based interphase coupling technology solved the interphase force and could be used to acquire accurate particle motion trajectories. The effect mechanism of fluid–solid transfer courses in the double-layered mixing tank with a draft tube can be obtained by analyzing key features, including velocity distribution, circulation flows, power, and particle characteristics. The research results illustrate that the draft tube structure creates two major circulations in the mixing transfer process and changes particle and vortex flow patterns. The circulating motion of the double-layered impellers strengthens the overall fluid circulation, enhances the overall mixing efficiency of the fluid medium, and reduces particle deposition. Numerical results can offer technical guidance for the chemical extraction course and lithium battery slurry mixing. [ABSTRACT FROM AUTHOR]

Recanalization poses challenges after coil embolization in cerebral aneurysms. Establishing predictive models for postembolization recanalization is important for clinical decision making. However, conventional statistical and machine learning (ML) models may overlook critical parameters during the initial selection process. In this study, we automated the identification of significant hemodynamic parameters using a PointNet-based deep neural network (DNN), leveraging their three-dimensional spatial features. Further feature analysis was conducted using saliency mapping, an explainable artificial intelligence (XAI) technique. The study encompassed the analysis of velocity, pressure, and wall shear stress in both precoiling and postcoiling models derived from computational fluid dynamics simulations for 58 aneurysms. Velocity was identified as the most pivotal parameter, supported by the lowest P value from statistical analysis and the highest area under the receiver operating characteristic curves/precision-recall curves values from the DNN model. Moreover, visual XAI analysis showed that robust injection flow zones, with notable impingement points in precoiling models, as well as pronounced interplay between flow dynamics and the coiling plane, were important three-dimensional features in identifying the recanalized aneurysms. The combination of DNN and XAI was found to be an accurate and explainable approach not only at predicting postembolization recanalization but also at discovering unknown features in the future. [ABSTRACT FROM AUTHOR]

An experimental investigation of R245fa flow boiling in the horizontal flow (θ fd = 0°), vertical upward flow (θ fd = 90°), and vertical downward flow (θ fd = –90°) was carried out using a bare stainless-steel tube (BT) with an inner diameter of 10.02 mm and an effective heating length of 820 mm. The experimental condition was performed under a saturation pressure of 0.6 MPa, a heat flux varying from 4.99–74.60 kW/m2, a mass flux range of 197.94–696.63 kg/(m2·s), and a vapour quality range from 0.01 to 0.9. Five flow patterns, stratified flow, intermittent flow, churn flow, annular flow, and drying flow, could be observed in the experiment. When the heat flux was relatively low (q ≤ 15 kW/m2)), the variation of the heat transfer coefficient with flow direction was relatively gradual. However, when q ≥ 30 kW/m2, a distinct 'U'-shaped trend in the heat transfer coefficient is observed with the flow direction transitioning from vertical downward to horizontal and then to vertical upward. Due to the effect of buoyancy force, the heat transfer performance was relatively better at θ fd = –90° The friction pressure drop in the horizontal flow was the smallest, and the maximum value always occurred at θ fd = 90° Meanwhile, the experimental data for heat transfer coefficient and pressure drop was compared to the well-known correlations from the literature. The predictive correlation by Fang et al. for the heat transfer coefficient was in good agreement with the experimental data. Regarding frictional pressure drop, the Filho, Muller-Steinhagen and Heck and Zakaria correlations were recommended for pressure drop in horizontal flow, upward flow, and downward flow, respectively. [ABSTRACT FROM AUTHOR]

Spur dikes are structures built along riverbanks that serve two purposes: stabilizing the banks and minimizing erosion risk by controlling water flow in the river channel. The current study used L-shaped spur dikes in an alluvial channel to analyze the bed morphology and flow pattern in the spur dikes zone with the influence of no-seepage and two distinct seepage velocities, V S 1 = 0.075 mm/s and V S 2 = 0.15 mm/s near the channel bed z / h < 0.2. The experimental study was also done to examine and compare the transformation in the local scour depth for the seepage condition. According to the study results, downward seepage movement causes significant modification in the channel's bed elevation and the development of scour depth. Observations indicate that the maximum local scour occurs at the first spur dike's leading edge. Seepage velocity V S 1 results in a 16.1% increase in the maximum scour depth compared to the no-seepage scenario. In comparison, seepage velocity V S 2 causes an increase of 25.2% in the maximum scour depth. Due to downward seepage, the flow distribution is shifted down near the channel's boundary. With an increase in the seepage rate, the magnitude of velocity, Reynold shear stress, turbulent kinetic energy, and bed shear stress also rise close to the channel's boundary. The current study also examined bursting events near the channel's bed under seepage and no-seepage conditions. These events included outward interaction, inward interaction, ejection, and sweep. Quadrant analysis of velocimeter data revealed that ejection and sweep were the dominant events contributing to the production of Reynolds shear stress in seepage and no-seepage flows. Meanwhile, outward interactions and inward interactions made minor contributions compared to ejection and sweep events to the Reynolds shear stress. [ABSTRACT FROM AUTHOR]

Purpose: The cross-limb (CL) technique is a commonly used endovascular treatment for addressing unfavorable anatomical features in patients with abdominal aortic aneurysm (AAA). The configuration of CL stent-graft plays a critical role in determining the postoperative hemodynamic properties and physiological behaviors, which ultimately impact the efficacy and safety of endovascular AAA treatment. This study aims to investigate the relationship between hemodynamics and CL stent-graft configuration from a hemodynamic perspective. Methods: Five distinct geometric models of cross-limb (CL) stent-graft configurations were constructed by optimizing the real clinical computed tomography angiography (CTA) data. These models varied in main body lengths and cross angles and were used to perform numerical simulations to analyze various hemodynamic parameters. Flow pattern, distribution of wall shear stress (WSS)-related parameters, localized normalized helicity (LNH), pressure drop, and the displacement force of all models were examined in this paper. Results: In patient-specific cases, helical flow and WSS increase with the main body. However, it also generated secondary flow in localized areas, leading to increased oscillation in the WSS direction. Notably, increasing the stent graft's main body length or decreasing the cross angle reduced the displacement force exerted on the stent-graft. Reducing the cross angle did not significantly alter the hemodynamic characteristics. Conclusion: In the clinical practice of CL deployment, it is crucial to carefully consider the stent-graft configuration and the patient specific to achieve optimal postoperative outcomes. This study provides valuable insights for guiding stent selection and treatment planning in patients with abdominal aortic aneurysm undergoing CL techniques, from a hemodynamic perspective. [ABSTRACT FROM AUTHOR]

The hydrodynamic characteristic of the multiphase mixed-transport pipeline is essential to guarantee safe and sustainable oil–gas transport when extracting offshore oil and gas resources. The gas–liquid two-phase transport phenomena lead to unstable flow, which significantly impacts pipeline deformation and can cause damage to the pipeline system. The formation mechanism of the mixed-transport pipeline slug flow faces significant challenges. This paper studies the formation mechanism of two-phase slug flows in mixed-transport pipelines with multiple inlet structures. A VOF-based gas–liquid slug flow mechanical model with multiple inlets is set up. With the volumetric force source term modifying strategy, the formation mechanism and flow patterns of slug flows are obtained. The research results show that the presented strategy and optimization design method can effectively simulate the formation and evolution trends of gas–liquid slug flows. Due to the convective shock process in the eight branch pipes, a bias flow phenomenon exists in the initial state and causes flow patterns to be unsteady. The gas–liquid mixture becomes relatively uniform after the flow field stabilizes. The design of the bent pipe structure results in an unbalanced flow velocity distribution and turbulence viscosity on both sides, presenting a banded distribution characteristic. The bend structure can reduce the bias phenomenon and improve sustainable transport stability. These findings provide theoretical guidance for fluid dynamics research in offshore oil and gas and chemical processes, and also offer technical support for mixed-transport pipeline sustainability transport and optimization design of channel structures. [ABSTRACT FROM AUTHOR]

Currently, microchannels are widely used in liquid-liquid heterogeneous mass transfer systems due to its excellent mass transfer performance. However, because of the passive mixing principle of traditional microchannels, the improvement of mass transfer performance has a bottleneck. This work proposes a novel rotating millimeter channel reactor (RMCR), capable of achieving liquid-liquid heterogeneous mass transfer enhance by centrifugal force. Three typical flow patterns of slug flow, parallel-droplet flow, and parallel flow in the RMCR were observed by high-speed photography technology. The volumetric mass transfer coefficient (KOa) of the RMCR increased with the increase of the total volumetric flow rate and rotational speed (N) increased. Compared with N = 0 r/min, the KOa of the RMCR increases by 61.5 % at 200 r/min, ranging from 0.013 to 0.021 s−1. The RMCR proposed in this work is expected to be applied to the liquid-liquid heterogeneous mass transfer system with high processing capacity and easy plugging. [ABSTRACT FROM AUTHOR]

Hydrogen production from electrolytic water is one of the most crucial techniques for generating green hydrogen. If the flow of hydrogen gas and alkali water in the transportation pipe exhibits slug flow, vibrations may occur, leading to potential accidents. The study of preventing slug flow is significant for pipe design. However, currently, there is no available research on the gas-liquid two-phase flow patterns of hydrogen gas and alkali water. Therefore, this study investigates the gas-liquid two-phase flow patterns in the pipe transporting hydrogen gas and alkali water and provides recommendations to prevent slug flow. Firstly, a numerical model based on the Volume of Fluid (VOF) method is established to simulate the two-phase flow of hydrogen gas and alkali water. Then, the effects of hydrogen gas and alkali water flow rates, pipe orientation, pipe diameter, and pipe length on the gas-liquid two-phase flow patterns are studied. Subsequently, the two-phase flow patterns are analyzed under different pipe layouts, including horizontal-vertical pipes, horizontal-horizontal pipes, horizontal-vertical-horizontal pipes, etc. The research reveals that increasing the pipe diameter, reducing the pipe length and increasing the hydrogen gas flow rate can effectively prevent slug flow in vertical pipes. Additionally, horizontal pipes and horizontal-horizontal pipes are less likely to experience slug flow. Furthermore, the consecutive appearance of two elbows induces slug flow even at higher hydrogen apparent velocities. Extending the length of the pipe between two consecutive elbows can effectively suppress the occurrence of slug flow. The present work can provide an important reference for the design of pipes used in hydrogen production from electrolytic water. [Display omitted] • The flow pattern of hydrogen-alkali water two-phase flow is studied. • Six different structures of pipes are studied, especially those containing elbows. • Two consecutive elbows with short distances can easily induce a slug flow. • Altering flow rates and pipe structural parameters can suppress slug flow. [ABSTRACT FROM AUTHOR]

High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH3-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier. [ABSTRACT FROM AUTHOR]

AbstractMicrostructures on the sidewall or bottom wall, have shown excellent heat transfer performance in the single-phase convective heat transfer of microchannel heat sinks. For increasing the heat flux, phase-change heat transfer was highlighted as an effective approach. However, more complicated mechanisms of boiling heat transfer make less study focused on the microchannel with microstructure. In this work, a bionic microchannel with concave cavities and bionic ribs was proposed to enhance the boiling heat transfer. Numerical simulations, along with the volume of fluid (VOF) analysis combined with a phase-change model, were used to investigate the effect of the microstructure on the behavior of bubbles in the subcooled flow boiling. The results showed that the microstructure promotes bubble nucleation and the occurrence of more small bubbles around big bubbles. Thus, it enhances boiling heat transfer. Meanwhile, the microstructure was found to be beneficial in maintaining a stable liquid film evaporation under annular flow and suppressing boiling instability. Ultimately, compared with rectangular microchannels, the reported wall temperature and inlet pressure are more stable in the proposed bionic microchannel, the heat transfer coefficient and critical heat flux of the bionic microchannel were found to be 1.45 times higher, with mass flux G of 498 kg/(m2·s) and heat flux qw of 600 kW/m2. [ABSTRACT FROM AUTHOR]

This study investigates the effect of gravity on the flow pattern and thermal efficiency of a single-loop oscillatory heat pipe. To simulate the influence of gravity, the deployment angles of the mechanism are varied (30°, 45°, 60°, and 90°). OpenFoam software is implemented to model boiling and condensation in the oscillating heat pipe, utilizing the volume of fluid (VOF) method. The evaporator is supplied with 55.5 W of heat power, the condenser wall temperature is maintained at 300 K, and the filling ratio of heat transfer fluid (water) is 40%. The findings revealed that decrease in gravitational force results in the thermal resistance be increased and the thermal performance of heat pipes be diminished. Expectedly, the best thermal performance in the oscillating heat pipe is observed in vertical mode, however, this study also examines the influence of reduced gravity. The simulation results show that the bubble pattern is first initiated by the bubble nucleation at the start of the heating process. Consequently, by bubble coalescence the slug and annular regimes can be observed. The phenomenological analysis of the dissolution, bubble coalescence, growth, and contraction observed in this study are discussed. [ABSTRACT FROM AUTHOR]