Fluid Wall Research Articles

Bucket-Handle Mesenteric Tears: A Comprehensive Review of Their Presentation and Management

Bucket-handle mesenteric tears remain a diagnostic challenge for clinicians. We aim to review the literature, including a single-surgeon series, to better understand their presentation and management.Three electronic databases (Ovid Medline, Embase, and PubMed) were searched for original research articles, describing relevant cases, from database inception to October 2021 using the following Medical Subject Heading (MeSH) terms: mesenteric avulsion, mesenteric tear, and blunt abdominal trauma. A retrospective review of cases managed under a single surgeon at our unit was also performed. Data extracted included demographics, mechanism of injury, presenting features, diagnostic imaging, surgical management, and patient outcome.In total, 19 studies were identified, including 22 patients (median age 34.5 years). The most common cause of injury was seat-belted road traffic accidents (77.3%), and patients commonly presented with abdominal pain (72.7%), tenderness (50%), positive seat-belt sign (54.5%), and haemodynamic compromise (45.5%). Computerised tomography scanning was the main imaging modality (68%), and the most common findings reported were abdominal free fluid (36.4%) and abdominal wall hernia (27.3%). The majority of patients were operated on within 24 hours of injury (68%), had a median length of stay of 14.5 days, and experienced an uncomplicated recovery (68%). There was no association between the development of complications and delayed surgical intervention >24 hours (p = 0.145). Our institution’s experience was similar, with 50% of patients undergoing surgical intervention within 24 hours. The median age was 32.5 years (50% female), and the median length of stay was 11 days.A high index of suspicion, serial monitoring, including blood tests, and imaging, with a low threshold for early repeat imaging, can provide a useful guide for identifying patients with bucket-handle tears.

Intrafollicular injection of nanomolecules for advancing knowledge on folliculogenesis in livestock

Despite the progress in assisted reproductive techniques, there is still a lack of rapid and minimally invasive in situ approaches for further enhancements of female fertility. Therefore, we synthesized clinically relevant liposome nanoparticles for ovarian intrafollicular injection to allow in vivo cellular imaging for future drug delivery, using the mare as an animal model. Ovarian follicles of living mares were injected in vivo with fluorescently labeled liposomes. Samples of the follicular wall (mural granulosa, theca interna, and theca externa), granulosa cells, and follicular fluid were harvested 24 h post-injection through the follicle wall biopsy (FWB), flushing, and aspiration techniques, respectively, using a transvaginal ultrasound-guided approach. In parallel, post-mortem dissected, and cultured porcine antral follicles were microinjected with doxorubicin-encapsulated liposomes to assess intracellular delivery potential. All injected mare and pig follicles were macroscopically healthy, and fluorescence imaging revealed successful intrafollicular binding to mural granulosa cells and progressive migration of liposomes to other follicle cell layers (theca interna, and theca externa), regardless of the follicle size. Intracellular delivery of doxorubicin was confirmed in all porcine follicle wall cell types. We conclude that the intrafollicular injection of nanomolecules is a promising approach for real-time monitoring of intrafollicular processes and potential utilization of in vivo cellular drug delivery to assist in follicle disease treatments and fertility improvement.

Bridging confined phase behavior of CH[formula omitted]-CO[formula omitted] binary systems across scales

Phase behavior of confined fluids may deviate significantly from that of the bulk fluid due to the fluid–wall interactions being a significant portion of all intermolecular interactions under confinement. Despite recent advancements in understanding confined phase behavior of pure fluids, confined phase behavior of mixtures remains an understudied topic. In this work, we examine the confined phase behavior of a CH4-CO2 binary system by combining Monte Carlo (MC) simulations, a cubic equation of state (EoS), and the lattice Boltzmann method (LBM). First, the effects of confinement on density and phase distribution in nano-size pores are established using Gibbs Ensemble MC calculations, which produce precise results of liquid and vapor confined pressures and account for the modification of the phase change location. By comparing the phase envelopes of bulk and confined mixtures at a fixed temperature, it is observed that the phase envelopes shrink with reductions in pore size. Based on this observation, we extend a modified Peng–Robinson EoS, which was originally developed for pure fluids under confinement, to mixtures via van-der-Waals-type mixing rules and by accounting for shifts in the critical properties of confined CH4-CO2. The resulting phase envelopes are in good agreement with the MC data. In addition, a local density model is used in combination with the confined EoS to calculate adsorption isotherms of CH4-CO2 mixtures and to characterize the behavior of confined matter in nanopores. Finally, we incorporate this EoS in a multicomponent multiphase LBM that uses a pseudopotential model to represent intermolecular forces. This workflow utilizes multiscale simulation techniques to bridge the behavior of multicomponent systems across scales and to shed light on the confined phase behavior of CH4-CO2 binary systems.

Molecular Insights into the Wall Slip Behavior of Pseudoplastic Polymer Melt in Nanochannels during Micro Injection Molding

Wall slip directly affects the molding quality of plastic parts by influencing the stability of the filling flow field during micro injection molding. The accurate modeling of wall slip in nanochannels has been a great challenge for pseudoplastic polymer melts. Here, an effective modeling method for polymer melt flow in nanochannels based on united-atom molecular dynamics simulations is presented. The effects of driving forces and wall–fluid interactions on the behavior of polyethylene melt under Poiseuille flow conditions were investigated by characterizing the slip velocity, dynamics information of the flow process, and spatial configuration parameters of molecular chains. The results indicated that the united-atom molecular dynamics model could better describe the pseudoplastic behavior in nanochannels than the commonly used finitely extensible nonlinear elastic (FENE) model. It was found that the slip velocity could be increased with increasing driving force and show completely opposite variation trends under different orders of magnitude of the wall–fluid interactions. The influence mechanism was interpreted by the density distribution and molecular chain structure parameters, including disentanglement and orientation, which also coincides with the change in the radius of gyration.

Computation of thermal energy in a rectangular cavity with a heated top wall

A heat exchanger is a device that transmits heat energy from one object to another, or within the same object. Examples of heat exchanger include a boiler, an oven and a cooker. Experimental techniques for testing these devices make it more costly and time-consuming. Consequently, computational fluid dynamics (CFD) can manage heat exchanger systems and their performance with ease. The actual impacts of what is being examined may then be predicted computationally which yields a precise output with approximate results. The designed geometry includes a rectangular duct with an inlet, outlet and two obstacles of equal height. The Navier–Stokes equations for the fluid flow are used. During the meshing process, the continuous geometric space of an item is divided into thousands or more forms, which helps to correctly identify the object’s physical shape. The desired model is computed numerically. Finite volume method (FVM) is used to study the results at a low Reynolds number (around [Formula: see text]. The goal is to theoretically analyze the transmission of heat and fluid resistance to the flow. The CFD findings with experimental data are compared to confirm the model predictions. A CFD model based on the FVM and experimental data from a flow cell is used to study how fluid moves through ducts. This study focuses on the pressure, velocity and temperature fields of a fluid moving through a rectangular duct. As the top wall fluid temperature rises, the temperature distribution changes. Increasing fluid flow declines the temperature distribution. Temperature distribution grows with duct heat flow. As the flow rate rises, so does dispersion. Furthermore, as flow rate and velocity distribution drop, pressure distribution rises.

Numerical studys on passive paramerters of a fluid-solid interaction problem derived by natural convection in a circular enclosure

The natural convection through a partitioned circular enclosure by a deformable middle wall was analyzed. To solve the FSI problem, a forceful connection between the fluid and flexible wall was established. In order to solve the problem under consideration, the Arbitrary Lagrangian-Eulerian (ALE) perspective was utilized. The finite element method (FEM), was also unilized in solving a set of model equations. Effect of wall Angle (30 ≤ η ≤ 90), flexibility (0.71 ≤ Eτ ≤ 200), Position of heat source and sink (-60 ≤ α ≤ +60) has been studied within a circular enclosure. The results indicate that a reduction in flexibility reduces the force (stress) applied to the wall as well as the average Nusselt number to some extent. Also, Increased angle of the wall leads to an enhancement in the Nu. The maximum applied stress and also wall distortion occur at specific positions of hot and cold sector, the buoyancy force and, therefore, the strength of the fluid flow are also higher, causing the heat transfer rate to increase. For The average Nusselt number, A decrease of 8.5 % for η = 90° has been reported compared to η = 30°. Also, the average Nusselt number for α = −60° is up to 124.5 % higher than for α = 60°.

Rheo-Engineered Microfluidics @ UNINA

<h2>Abstract</h2> The interest in microfluidic applications based on complex fluids is a result of the unique fluid dynamics of these systems, which enable the creation of effective devices for health care or biological and chemical analysis. In this area, processing suspensions of rigid particles in viscoelastic liquids offers a variety of possible applications where the rheology plays a key role. This contribution presents our activities on viscoelasticity-driven microfluidic applications with rigid particles. The effects of the fluid rheology, particle shape, channel geometry, wall properties, and particle volume fraction are addressed.

The Force on a Magneto-spherical Particle Oscillating in a viscous Fluid Perpendicular to an Impermeable Planar Wall with Slippage

The effect of a magnetic field and slip on the motion of a solid sphere moving perpendicular to an unbounded rigid wall in an unlimited viscous fluid is investigated. As the sphere vibrates perpendicularly to the rigid wall, its center line is accompanied by a low amplitude vibration. A slip condition is applied to the sphere surface, while a no-slip dynamic condition is applied to the wall. Additionally, a semi-analytical method and a numerical scheme using collocation are presented. Furthermore, we calculate the amplitude of the non-dimensional coefficients of drag force acting on the solid sphere using various values of frequency, separation, and magnetic parameters. In addition, streamlines are plotted. The results of the magnitude normalized drag force are compared with those in previous literature.

Culture-dependent evaluation of the respiratory microbiome in children with cystic fibrosis

The study aimed to assess the regional peculiarities of the respiratory profile of children with cystic fibrosis (CF) in the Dnipro region (Ukraine).&#x0D; Methods. Children living in the Dnipro region and aged younger than 18 years old with molecular-genetic confirmation of CF were enrolled in the study. Lung colonization was evaluated using a culture-dependent method. Sputum, mucus from the posterior pharyngeal wall and bronchoalveolar lavage fluid (BALF) were utilized.&#x0D; Results. The Firmicutes phylum was the most common and occupied 54.00 % of the general proportion. On the other hand, the Proteobacteria phylum demonstrated overexpression in CF airways and kept the second rank with 28.87 %.&#x0D; Sorensen's species similarity coefficient showed an allied affinity between the microbial burden of oropharyngeal samples with nasopharyngeal and sputum, QS = 0.61 and 0.91, respectively. However, the species composition within the nasal cavity was distinct from sputum and BALF (QS=0.47).&#x0D; The primary pathogens in childhood were S. aureus, H. influenza, P. aeruginosa and A. fumigatus. In contrast to gram-negative non-fermenters (GNNF), the prevalence of S. aureus isolates by age had a non-linear character. The commensal microbiota changed negatively with age. Among children under 12 years, the Streptococcus genus was identified in 23.08 % of the samples, but among the age category older than 15 – only in 9.22 %.&#x0D; 11.06 % of S. aureus had small colony variants (SCVs) morphotypes. Isolates of P. aeruginosa with the properties of SCVs were also found in children who underwent prolonged antimicrobial treatment. However, the most prominent was the mucoid phenotype – 34.31 % of isolates.&#x0D; Conclusions. Along with conventional microbiological properties, obligate pathobionts in children with CF exhibited changes, resulting in difficulties in identification. These included auxotrophic modification into SCVs and mucoid transformation.&#x0D; The culture-dependent technique gives crucial data about the profile of pathogens usually associated with CF, although it is sufficiently limited

Integrating particle tracking with computational fluid dynamics to assess haemodynamic perturbation by coronary artery stents.

AimsCoronary artery stents have profound effects on arterial function by altering fluid flow mass transport and wall shear stress. We developed a new integrated methodology to analyse the effects of stents on mass transport and shear stress to inform the design of haemodynamically-favourable stents.Methods and resultsStents were deployed in model vessels followed by tracking of fluorescent particles under flow. Parallel analyses involved high-resolution micro-computed tomography scanning followed by computational fluid dynamics simulations to assess wall shear stress distribution. Several stent designs were analysed to assess whether the workflow was robust for diverse strut geometries. Stents had striking effects on fluid flow streamlines, flow separation or funnelling, and the accumulation of particles at areas of complex geometry that were tightly coupled to stent shape. CFD analysis revealed that stents had a major influence on wall shear stress magnitude, direction and distribution and this was highly sensitive to geometry.ConclusionsIntegration of particle tracking with CFD allows assessment of fluid flow and shear stress in stented arteries in unprecedented detail. Deleterious flow perturbations, such as accumulation of particles at struts and non-physiological shear stress, were highly sensitive to individual stent geometry. Novel designs for stents should be tested for mass transport and shear stress which are important effectors of vascular health and repair.

A computational conjugate heat transfer study of a rectangular minichannel undergoing sinusoidal flow pulsations

The development of current and next generation high performance electronic devices has led to smaller components in more densely packed spaces. The increasing power levels have resulted in ever-increasing heat flux densities which necessitates the evolution of new liquid-based heat exchange technologies. Pulsating flow in single-phase cooling systems is viewed as a potential solution to the problems involving high heat flux densities. A review of published literature indicates a lack of time-resolved and space-resolved links between the hydrodynamic pulsating characteristics and associated heat transfer perturbations. The scope of this work involves the development of a validated three-dimensional conjugate heat transfer computational model to investigate hydrodynamically and thermally fully developed pulsating flows in a heated rectangular minichannel. Simulations were performed for a sinusoidal waveform with a fixed pulsation amplitude for varying pulsation frequencies in the range of 0.02 Hz to 25 Hz, corresponding to Womersley numbers in the range of 0.5 ≤Wo≤ 18.33. Low pulsation frequencies exhibited the well known parabolic profile for the fluctuating hydrodynamic and thermal parameters, i.e., velocity, wall shear, and wall temperature. As a result, the axial pressure gradient, velocity, and wall shear stress profiles were in phase and similar results were obtained for the oscillating wall and bulk fluid temperatures. For the inertia dominated high frequency flows, an increase in axial pressure gradient leads to a phase lag of π/2 when compared with the velocity and wall shear profiles. The shorter time period pulsations exhibit unique attributes in the form of flow reversal effects at local near wall regions. High near wall thermal gradients were observed as a result of stronger viscous effects due to a narrowing thermal boundary layer; consequently the transverse diffusion of heat was ineffective. A phase lag and a subsequent drop in the peak magnitudes existed between the oscillating bulk and wall temperatures for high frequency flows. Fluctuations in near wall heat flux profiles showed a dependency on the imposed pulsation frequencies. For the chosen pulsation profile and frequencies, the overall time averaged thermal performance indicates that pulsating flow performs worse than steady flow for a flow rate amplitude of 1. The highest thermal performance was achieved for Wo=5.1 while maintaining a low friction factor.

Rare Time Series of Hydrothermal Fluids for a Submarine Volcano: 14 Years of Vent Fluid Compositions for Brothers Volcano, Kermadec Arc, New Zealand

AbstractHydrothermal vent fluids from Brothers submarine arc volcano were previously collected in 2004, 2005, and 2017. We present new data from 2018 along with a unique time series of a submarine volcano hosting two distinct types of hydrothermal venting to better understand subsurface processes and how they evolve over time. Samples were collected from known venting locations along the NW Caldera, the Upper and Lower Cone sites, and the newly sampled Upper Caldera site. The NW Caldera wall and Upper Caldera vent fluid compositions are controlled by high-temperature water-rock interactions and phase separation between 2004 and 2018. Fe/Mn molar values suggest that the magmatic impact on all fields has been increasing over time. The Upper Cone has varying influences, including short-term pulses of magmatic degassing, as revealed in K-Mg-SO4 ternary diagrams, Fe/Mn values, and δD and δ18O data. The Lower Cone is dominated by low temperatures and CO2 degassing and shows a pulse in magmatic influence in 2017, followed by a decrease toward earlier conditions in 2018. The 2017 pulse was accompanied by the increase of an enigmatic, soluble MgSO4 phase, potentially due to the “mining” of a magmatic brine sequestered inside the cone. Stable isotope data across the sites indicate pulses of magmatic waters in 2004 and 2017, immediately followed by episodes of more seawater-dominated fluids in 2005 and 2018. Magmatic degassing, phase separation, permeability, and mineral solubility all strongly influence changes in vent fluid composition. This study highlights the dynamic nature of the Brothers volcano hydrothermal system and the changes in fluid chemistry that may affect resultant mineralization.

Analysis of the scaling mechanism and characteristics of a double-defects screen based on data from Hafaya oilfield

Corrosion defects of screen occurred frequently in sand control process due to the influence of formation factors. The main purpose of this study was to analyze screen scaling based on field data with CFD technology under different sizes, quantities and distribution modes of corrosion defects. A full presentation of turbulent Kinetic Energy contours, wall shear stress contours, fluid velocity and temperature on the screen surface are presented and discussed in the process of scaling. The distribution characteristics of CaCO3 in the scaling model were used to characterize the scaling characteristics. Furthermore, prediction model of scaling thickness was established to systematically evaluate the results. The conclusion of numerical analysis showed that with other conditions unchanged, the scale of radial distribution is larger than that of axial distribution. More over, the larger the defect width and distance, the less obvious scaling. However, the defect depth indicated the opposite results, which meant that the size factor has the greatest influence on scaling. Keeping the environmental conditions changed, velocity and temperature showed obvious influence on particle scaling. It reveals that the velocity of produced liquid has a great influence on the defect screen with different distribution modes.When the size condition of the defect were kept remained, the scaling amount of screen increases obviously with the increase of velocity. The influence of temperature on the two different distribution patterns of defects was not obvious. With the increased of the temperature, the amount of scaling in the pipe also increased similarly. Considering the results, this research could be used as basis to offer safe operating guidelines to reduce the scaling in the screen due to corrosion defects in oil production. To mitigate the impact of this factor on production, scaling can be addressed by reasonably increasing the velocity of the produced liquid and lowering the temperature with the defects exist.

Transducer Design for Clamp-on Guided Wave Flow Measurement in Thin-Walled Pipes

Clamp-on ultrasonic transit time difference flow meters provide opportunities for metering where it is impractical or undesirable to cut into an existing pipeline to install an alternative flow meter. Up until now, it has been difficult to perform this type of measurement on thin-walled metal pipes, due to the difficulty of interpreting the guided wave modes in the combined pipe wall and internal fluid system, but a new method has been reported recently that utilises these guided wave modes for flow measurement. Through computational modelling, and construction and testing of different transducers, the design considerations for clamp-on transducers are highlighted and their impact on guided wave flow rate measurement is evaluated. The design features considered include a curved contact face to provide focusing of the ultrasound within the pipe and a scattering surface to reduce internal reflections. It is found that additional unwanted ultrasonic modes can be minimised by ultrasonic transducer wedge design features such as profiling the curvature of the transducer to conform to the pipe wall or creating a scattering edge to minimise internal wedge reflections. It is also observed that minimising these unwanted modes does not offer any advantage for the transit time difference measurement used in calculating flow.

Reconfigurable Microfluidic Circuits for Isolating and Retrieving Cells of Interest.

Microfluidic devices are widely used in many fields of biology, but a key limitation is that cells are typically surrounded by solid walls, making it hard to access those that exhibit a specific phenotype for further study. Here, we provide a general and flexible solution to this problem that exploits the remarkable properties of microfluidic circuits with fluid walls—transparent interfaces between culture media and an immiscible fluorocarbon that are easily pierced with pipets. We provide two proofs of concept in which specific cell subpopulations are isolated and recovered: (i) murine macrophages chemotaxing toward complement component 5a and (ii) bacteria (Pseudomonas aeruginosa) in developing biofilms that migrate toward antibiotics. We build circuits in minutes on standard Petri dishes, add cells, pump in laminar streams so molecular diffusion creates attractant gradients, acquire time-lapse images, and isolate desired subpopulations in real time by building fluid walls around migrating cells with an accuracy of tens of micrometers using 3D printed adaptors that convert conventional microscopes into wall-building machines. Our method allows live cells of interest to be easily extracted from microfluidic devices for downstream analyses.

Sulfur formation associated with coexisting sulfide minerals in the Kemp Caldera hydrothermal system, Scotia Sea

The Kemp Caldera is a submarine caldera located in the southernmost part of the intra-oceanic South Sandwich arc, Scotia Sea. The caldera comprises a unique hydrothermal system in which elemental sulfur (S0) coexists with sulfide minerals at unusually high pH-values (pH25 °C > 5). During the 2019 R/V Polarstern PS119 expedition, samples from the white smoker vent fields in the center of the caldera were recovered by a remotely operated vehicle. The sampling of elemental sulfur took place at the vent sites “Great Wall” and “Toxic Castle”, which are located < 80 m apart. At Great Wall, sulfur is fine-crystalline, while at Toxic Castle S0 occurs in liquid form, forming amorphous and globular structures. Here, tabular plates of covellite are found as inclusions in the quenched sulfur. The fluids from both sites have pH-values of about 5.4 to 5.7 (at 25 °C) and show a relatively wide temperature range from 63 to > 200 °C. The isotope values of sulfide and elemental sulfur range from 4.6 to 5.8 ‰, while sulfate concentrations at Great Wall are lower than in seawater.Elemental sulfur in submarine arc/back-arc systems is commonly believed to form by disproportionation of SO2. It generally shows negative δ34S values and precipitates from acid-sulfate type hydrothermal fluids with pH-values as low as < 1. This formation mechanism, however, cannot explain the high pH and low sulfate concentration of the Great Wall fluid alongside high δ34S values of elemental sulfur and massive sulfides found at Kemp. Instead, we suggest that S0 formation at Kemp Caldera can be attributed to synproportionation of SO2 and H2S. This formation mechanism is thermodynamically feasible but has not been demonstrated to actually take place in hydrothermal systems. The association of elemental sulfur with covellite is also uncommon, but not unexpected in magmatic-hydrothermal systems. The uncommonly high pH-value is likely responsible for the precipitation of the metal sulfides, which are unusual for known acid-sulfate systems studied to date. Our study shows that the geochemical behavior of sulfur in arc/back-arc hydrothermal systems is more diverse than previously recognized.

Entropy analysis of MHD flow of Jeffrey fluid in an inclined channel

AbstractThis study is aimed at investigating the influence of entropy analysis of magnetohydrodynamic flow of Jeffrey fluid in an inclined micro‐channel in the presence of thermal radiation and field suction/injection. We have improved the mathematical model of the physical problem under consideration. The designed equations have been solved by applying the shooting‐based fourth‐order, Runge–Kutta method with the boundary conditions, which describe velocity slip and temperature jump conditions at the fluid–wall inter‐face. Numerical efforts are described graphically and mentioned quantitatively concerning different parameters such as Jeffery parameter, Bejan number, and entropy generation embedded in the problem. The numerical results for the expression of the irreversibility ratio are obtained. It is observed that the wall inclination strengthens the entropy production rate in the micro‐channel, and the thermal buoyancy layer induces an increase in fluid velocity as suction.

Experimental Study on Proppant Transport within Complex Fractures

Summary The process of proppant filling within complex fractures is a key factor that determines the effects of volumetric fracturing operation in shale. To address the need of simulating proppant transport within the complex fractures, a large size visual simulation equipment of particle transport within complex fractures was built. The equipment considers roughness and fluid leakoff on the fracture wall and includes branched fractures of different angles. We ensured that the fluid flow and proppant flow were similar to those in the actual fracture and carried out experiments to obtain the influence of operation parameters and fracture parameters on proppant transport, also including injection of special proppants and channel fracturing. Then, we quantified proppant placement through standardized processing of dune shape pictures. The results show that under the influence of perforation, the near-wellbore dune is distributed in a slope shape, and an increase in the perforation density causes dune migration toward the wellbore and proppant accumulation to a certain height within the wellbore. The carrier fluid flow velocity change from 1.0 to 1.5 m/s within the fracture has the greatest effect on the dune equilibrium height (DEH). The dune height only varies slightly after the proppant concentration reaches 12%. Small size proppants have better transport capacity in the slickwater, and the large size proppants are likely to settle down. Combination injection of increasing proppant size improves the filling effect of complex fractures significantly. Pulse injection and stopping pump during fracturing operation have little effect on the transport of conventional proppants. Nevertheless, stopping pump leads to a significant increase in the dune height of the lower density proppants. An increase in the flow rate within the branched fracture leads to the transition in the dune shape from triangle to trapezoid and rectangle. The dune height within the major fracture determines those within the branched fracture, and the proppant volume flowing into the branched fracture determines the dune length. Proppant accumulation within the branched fracture enhances the difficulty in the diversion of carrier fluid to the branched fracture. The proppant tumble area increases within the inclined fracture, which is conductive to proppant transport. The proppants form the dune through bridging within the horizontal fracture, and the dune is less stable than that within the vertical fracture. A reduction in the proppant density and size leads to a significant increase in the proppant transport distance, and the convection effect by concentration difference of the ultralow-density (ULD) proppant is of great significance for propping of the microfractures. In channel fracturing, the proppant and fiber agglomerates are formed at the fracture point with the relatively large fluid leakoff and wall roughness, and the agglomerates grow laterally against the fracture fluid flow direction. A reasonable increase in the injection rate enhances the connectivity between the channels within the fracture. This study provides guidance for the optimization of volumetric fracturing parameters.

Automatic measurement of fetal head circumference using a novel GCN-assisted deep convolutional network

The growth of the fetus can be effectively monitored by measuring the fetal head circumference (HC) in ultrasound images. Moreover, it is the key to assessing the fetus's health. Ultrasound fetal head image boundary is blurred. The ultrasound sound shadow results in a partial absence of the skull in the image. The amniotic fluid and uterine wall form a structure similar to the head texture and grayscale. All these factors result in challenges to ultrasound fetal head edge detection. The new convolutional neural network (CNN) named GAC Net was proposed in this paper, which can effectively solve the above problems. GAC Net is an end-to-end network model constructed by the encoder and decoder. In order to suppress the interference of ultrasound image quality defects on the HC measurement, the graph convolutional network (GCN) module was added to the connection channel between the encoder and the decoder. The new attention mechanism enhanced the network's ability to perceive border areas. Experiments were performed on the HC18 fetal head ultrasound image data set. The following objective evaluation indicators were calculated, including the Hausdorff distance (HD), the absolute difference (AD), the difference (DF), and the Dice similarity coefficient (DSC) of head circumference. Experimental results showed that GAC-Net had an HD of 1.22 ± 0.71 mm, an AD of 1.75 ± 1.71 mm, a DF of 0.19 ± 2.32 mm, and a DSC of 98.21 ± 1.16%. The overall performance of the proposed algorithm exceeded the state-of-the-art methods, which fully proved the effectiveness of the GAC Net presented in this paper.

Effects of electrically conductive walls on turbulent magnetohydrodynamic flow in a continuous casting mold

In the present study, we have performed a series of numerical simulations of the turbulent liquid metal flow in a laboratory-scale setup of the continuous casting. The liquid metal flow was subjected to an external non-uniform magnetic field reproducing a realistic electromagnetic brake (EMBr) effect. The focus of this research was on the effects of the finite electrical conductivity of Hartmann walls on the flow and turbulence in the mold. To be able to simulate distributions of the electric potential and current in both the fluid and solid wall domains, we applied our recently developed and validated in-house conjugate MHD solver based on the open-source code OpenFOAM. The dynamic Large Eddy Simulation (LES) method was used to simulate the turbulent flow. The results obtained for the neutral (non-MHD) and MHD cases over a range of the imposed EMBr strengths – all for the perfectly electrically insulated walls – were compared with the available Ultrasound Doppler Velocimetry (UDV) measurements. A good agreement between simulations and experiments was obtained for all simulated cases. Next, we completed a series of simulations including a wide range of the finite electric conductivities (ranging from a weakly to perfectly conducting wall conditions) of the Hartmann walls for a fixed value of the imposed EMBr. The obtained results demonstrated a significant influence of the electric wall conductivities on the flow and turbulence reorganization. It is expected that here provided insights can be applicable for the new generation of the laboratory- and real-scale continuous casting setups.