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To analyze the influence of different ignition positions on the propagation of deflagration characteristics and the disaster mechanism in the hydrogen deflagration process in the tunnel, this study compares and verifies the experimental data of tunnel model deflagration based on the CFD code GASFLOW-MPI. A combustion velocity model based on the accelerated separation effect is used, and the effect of heat transfer on the consequences of deflagration is considered. The propagation laws of pressure waves, fluid velocity and temperature in the tunnel are analyzed, and it is found that the changing trends of shock waves and fluid velocity in the tunnel are consistent, but completely opposite in the tunnel outside. The effects of different ignition positions on the hydrogen deflagration characteristics are compared and analyzed. The results show that when ignition occurs at different heights of the center of the premixed region, the impact on the deflagration characteristics is relatively small, while when ignition occurs at different horizontal distances in the premixed region, the impact on the deflagration characteristics is relatively large; the peak overpressure of side ignition is far lower than the case where ignition occurs in the center of the premixed region, but the maximum flow velocity is much higher than the center ignition. The impact on temperature is the smallest. In general, in areas close to the hydrogen/air premixed zone, side ignition results in more severe consequences, whereas in areas far from the premixed zone and outside the tunnel, central ignition leads to more severe consequences. This study provides theoretical support for understanding the disaster-causing mechanisms of hydrogen/air premixed gas deflagration in tunnels under different ignition positions. • Deflagration behaviors of hydrogen-air mixtures in the tunnel were studied. • Heat transfer and flame instability are taken into account in numerical simulations. • The deflagration consequences of different ignition positions are discussed. • Side ignition causes the least peak overpressure in the tunnel. [ABSTRACT FROM AUTHOR]

The study investigates the effect of tube shrinkage rate on the explosion characteristics of premixed hydrogen-air in a confined space using Large Eddy Simulation (LES). The wrinkle factor of the flame surface density model is dynamically modeled based on the Fureby and Muppala (FurebyM) model. The numerical results from this model can be better verified with previous experimental results. The results indicate that a lower shrinkage rate results in longer flame propagation time from the reducer region. The peak flame front velocities were 68.6 m/s, 83.6 m/s, 96.4 m/s, and 103.6 m/s for tube shrinkage rates of 0.25, 0.5, 0.75, and 1.0, respectively. There is also a negative correlation between explosion overpressure and varying shrinking rates. The split tulip flame forms at a shrinkage rate of 0.25. Analysis of the flame structure and velocity flow field suggests that this phenomenon may be related to the formation of multiple fish-tail vortex structures on the left side of the flame front. Moreover, the effect of different shrinkage rates on the flame structure and the velocity flow field before the propagation of the premixed flame to the reducer region is relatively insignificant for tube structures with different shrinkage rates. This study provides a theoretical basis for protection against confined space explosions with premixed hydrogen-air mixtures. • The wrinkle factor in the flame surface density model is dynamically modeled and the accuracy of the model is verified. • The effect of tube shrinkage on the deflagration characteristics of hydrogen-air was investigated. • The flame structure evolves into a split tulip flame for a shrinkage of 0.25. [ABSTRACT FROM AUTHOR]

Dynamic Ultrasound Localization Microscopy (DULM) has first been developed for non-invasive Pulsatility measurements in the rodent brain. DULM relies on the localization and tracking of microbubbles (MBs) injected into the bloodstream, to obtain highly resolved velocity and density cine-loops. Previous DULM techniques required ECG-gating, limiting its application to specific datasets, and increasing acquisition time. The objective of this study is to eliminate the need for ECG-gating in DULM experiments by introducing a motion-matching method for time registration. We developed a motion-matching algorithm based on tissue Doppler that leverages the cyclic tissue motion within the brain. Tissue Doppler was estimated for each group of frames in the acquisitions, at multiple locations identified as local maxima in the skin above the skull. Subsequently, each group of frames was time-registered to a reference group by delaying it based on the maximum correlation value between their respective tissue Doppler signals. This synchronization ensured that each group of frames aligned with the brain tissue motion of the reference group, and consequently, with its cardiac cycle. As a result, velocities of MBs could be averaged to retrieve flow velocity variations over time. Initially validated in ECG-gated acquisitions in a rat model (n = 1), the proposed method was successfully applied in a mice model in 2D (n = 3) and in a feline model in 3D (n = 1). Performing time-registration with the proposed motion-matching method or by using ECG-gating leads to similar results. For the first time, dynamic velocity and density cine-loops were extracted without the need for any information on the animal ECG, and complex dynamic markers such as the Pulsatility index were estimated. Results suggest that DULM can be performed without external gating, enabling the use of DULM on any ULM dataset where enough MBs are detectable. Time registration by motion-matching represents a significant advancement in DULM techniques, making DULM more accessible by simplifying its experimental complexity. [ABSTRACT FROM AUTHOR]

This research compares auxiliary energy-assisted friction stir welding (FSW) techniques with conventional FSW when joining dissimilar materials. Specifically, it conducts numerical modeling and experimental validation for the effectiveness of plasma-assisted FSW and induction-assisted FSW for DH36 steel and 6061-T6 aluminum alloy. Fully coupled 3D computational fluid dynamics (CFD) models, incorporating the multi-species transport method, were developed, where the species mass fractions of the workpieces are transported through diffusion, convection, and reaction sources for individual species. Based on the temperature validation, the dedicated heat flux based on the rectangular heat flux and Gaussian heat flux distribution were considered for induction coil and plasma arc heating on the DH36 steel side, respectively. The established conventional and auxiliary energy-assisted FSW models were validated against experimentally observed temperature fields and the joints' material features. Results indicate that the assistance of plasma and induction auxiliary energy sources increased the temperature field, strain rate, and flow velocity without forming stagnant zones on the steel side caused by reduced dynamic viscosity. In plasma arc-assisted FSW, the steel could not extrude effectively from the base steel sheet due to deficient heat and flow velocity input; therefore, defect-prone coarse steel fragments were blended with the Al matrix. In induction-assisted FSW, the uninterrupted steel layer was extruded from the steel side and placed on the Al side, which was caused by enhanced heat build-up and flow velocity. Moreover, induction-assisted FSW achieved symmetric material flow on both advancing and retreating sides, resulting in defect-free welds. [ABSTRACT FROM AUTHOR]

To determine the spray characteristics of internal-mixing gas-liquid injector under various operating conditions, the experimental facilities for spraying are established. By means of high-speed camera, laser particle size analyzer and PIVlab, the effects of gas and liquid flow conditions on the spray characteristics, such as position of jet impingement, spray angle, breakup length, velocity distribution and droplet size, have been investigated in detail. Experimental results demonstrated that there are two types of atomization for this injector, namely impact atomization and aerodynamic atomization. The impingement position of the liquid jets is outside of the injector exit. Alternatively, no impingement occurs between the jets. The spray angle increases with the increase of liquid flow rate, and decreases with the increase of gas flow rate. The breakup length decreases with the increase of the liquid or gas flow rate. The higher the liquid flow rate, the greater the velocity distributed along the axial and radial direction. However, the effect of gas flow rate on the velocity along the axial and radial directions acts differently at different spatial position. An increase in the liquid flow rate causes the droplet diameter to increase first and then decrease. The droplet size will decrease when the gas-liquid momentum ratio increases. • Two types of atomization process: "aerodynamics fragmentation" and "impact fragmentation". • Effects of gas/liquid flow rates on the position of jet impingement, spray angle, breakup length, velocity distribution and droplet size. • Effects of operating conditions on the two atomization mechanisms: "aerodynamics fragmentation" and "impact fragmentation". • The dominant factor (mutual impact between the liquid jets or gas-liquid interaction) in atomization process depends on the gas flow rate. [ABSTRACT FROM AUTHOR]

• Ammonia condensation has been experimentally studied in 8 mm and 11 mm tubes. • A new phenomenological model has been proposed for ammonia condensation. • The lowest condensation HTCs characterise the downstream flow. The paper proposes the experimental study of ammonia condensation in aluminium tubes with 8 mm and 11 mm internal diameters. The new study aimed to compare and extend the existing ammonia in-tube condensation data. The lines were tested mainly in horizontal configuration at mass velocities of 20 to 160 kg·m−2s−1, saturation temperature of 35 to 65 °C and inlet vapour quality of 0.1 to 0.9. Shah (1979), laminar-laminar Dobson and Chato (1998), and Cavallini et al. (2001) models predict well ammonia condensation HTCs at mass velocities of 120 to 160 kg·m−2s−1. A new phenomenological model has been proposed for the mass velocities of 20 to 120 kg·m−2s−1, predicting the test data with an accuracy of ±20 %. Similar ammonia condensation HTCs have been obtained for horizontal and upstream flows at a mass velocity above 120 kg·m−2s−1. The lowest condensation HTCs at the considered boundary conditions characterise the downstream configuration of an in-tube condenser at a mass velocity below 120 kg·m−2s−1. However, inclining the ID 8 mm tube by 15° from the normal substantially increases the condensation HTCs by 10 to 30 %, depending on vapour quality. At the inclinations of 15 to 45° from the horizontal line toward the downstream flow, the condensation HTCs exceed the ones of horizontal flow by 10 to 15 % at the vapour quality of <0.5 and low mass velocity of 80 kg·m−2s−1. [ABSTRACT FROM AUTHOR]

Lateral intakes are very important for diverting a portion of the river flow and providing the proper flow depth. In cases where small dams are used to operate and control the river's water level for the intake and to meet downstream water needs, the opening and closing of the dam gates before the construction of the intake and during its operation are important. In the current study, the problem of reducing the water head in the intake basin of the Hemmat dam pumping station, especially in the seasons of low water and the accumulation of sediment in the intake inlet of the Hemmat dam located in the Khuzestan province of Iran, has been investigated. Focusing on different arrangements of opening and closing gates, using a spur dike and flow rates of 143, 100, 62, 32, and 12 m3/s to investigate velocity changes and the depth of flow at the water inlet, computational fluid dynamics (CFD) simulations were done. With the spur dike, the water intake efficiency is increased by 384% compared to the project's current state (operation without any flow control structure), and the hydraulic conditions resulting in sedimentation are eliminated. The flow depth of the water intake channel, with the spur dike, increases by 10% compared to the condition without it. It is worth mentioning that gate management also affects water supply efficiency. The results of the current study are a good example of the successful application of computer simulations for sustainable systems engineering. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the impact of microbubble degradation and flow velocity on Sub-Harmonic Aided Pressure Estimation (SHAPE), and to explore the correlation between subharmonic amplitude and pressure as a single factor. We develop an open-loop vascular phantom platform system and utilize a commercial ultrasound machine and microbubbles for subharmonic imaging. Subharmonic amplitude was measured continuously at constant pressure and flow velocity to assess the impact of microbubble degradation. Flow velocity was varied within a range of 4–14 cm/s at constant pressure to investigate its relationship to subharmonic amplitude. Furthermore, pressure was varied within a range of 10–110 mm Hg at constant flow velocity to assess its isolated effect on subharmonic amplitude. Under constant pressure and flow velocity, subharmonic amplitude exhibited a continuous decrease at an average rate of 0.221 dB/min, signifying ongoing microbubble degradation during the experimental procedures. Subharmonic amplitude demonstrated a positive correlation with flow velocity, with a variation ratio of 0.423 dB/(cm/s). Under controlled conditions of microbubble degradation and flow velocity, a strong negative linear correlation was observed between pressure and subharmonic amplitude across different Mechanical Index (MI) settings (all R2 > 0.90). The sensitivity of SHAPE was determined to be 0.025 dB/mmHg at an MI of 0.04. The assessment of SHAPE sensitivity is affected by microbubble degradation and flow velocity. Excluding the aforementioned influencing factors, a strong linear negative correlation between pressure and subharmonic amplitude was still evident, albeit with a sensitivity coefficient lower than previously reported values. [ABSTRACT FROM AUTHOR]

Artificial waterways are characterized by dams and locks that slow water flow. Such conditions can influence the environment of freshwater organisms, including the zooplankton community. Our research aimed to assess the impact of environmental and hydrological conditions on the zooplankton of sites upstream and downstream of canal locks. The study was carried out in 2021 and 2022. Water samples were collected monthly from two canals during the growing season. We evaluated how water flow velocity and selected environmental parameters (i.e., water temperature, Secchi disk visibility, conductivity, oxygen concentration, saturation, pH and chl-a concentrations) influence the zooplankton diversity (T) density (N) and biomass (B). Our study showed that the zooplankton of the canals was highly diverse. Rotifers dominated over crustaceans in diversity and density at all sites of canals. The statistical analysis revealed differences in environmental and biological conditions between habitats located upstream and downstream of locks. Rotifers density and biomass changed approximately proportionally to changes in chlorophyll at sites upstream of locks. It supports the hypothesis that rotifer communities are defined by the bottom-up effect linked to food supply (phytoplankton). The growth of crustaceans (density and biomass), as well as total zooplankton biomass, was affected by water temperature at sites downstream of the lock. [ABSTRACT FROM AUTHOR]

To investigate the relationship between left atrial appendage (LAA) morphology, quantified based on fractal dimension (FD), and LAA hemodynamic parameters in patients with atrial fibrillation (AF), in an effort to reveal the effect of LAA shape on blood flow. 225 patients with AF who underwent cardiac computed tomography angiography (CTA) and transesophageal echocardiography (TEE) were enrolled. LAA morphology was quantified based on FD on cardiac CTA images, and LAA hemodynamic parameters, including injection fraction (EF), filling peak flow velocity (FV), maximum speed of emptying (PEV), and wall motion velocity (WMV), were assessed using TEE. We divided the patients with AF into two groups based on a mean LAA FD of 1.32: the low FD group (n=124) and the high FD group (n=101). Compared to the low FD group, there were more patients with LAA circulatory stasis/thrombus (P =0.008) in the high FD group, as well as lower LAA FV (P =0.004), LAA PEV (P =0.007), and LAA WMV (P =0.007). LAA FD was an independent and significant determinant of LAA EF (β = -11.755, P =0.001), LAA FV (β = -17.364, P =0.004), LAA PEV (β = -18.743, P <0.001), and LAA WMV (β = -7.740, P =0.001) in multiple linear regression analysis. LAA FD is an essential determinant of LAA hemodynamic parameters, suggesting that the relatively complex morphology of the LAA may influence its hemodynamics, which can correlate with embolic events. • To investigate the relationship between LAA FD and LAA hemodynamic parameters. • LAA FD was negatively associated with LAA EF, LAA FV, LAA PEV, and LAA WMV. • LAA FD was an independent determinant of LAA EF, LAA FV, LAA PEV, and LAA WMV. [ABSTRACT FROM AUTHOR]

Geobag stability has not been extensively studied under river current loading. In this study, the impacts of geobag characteristics (shape, bag material, and fill ratio of sand) and channel side slope (flat and 1V:2H) on a single geobag's stability were systematically investigated in a physical model to form the solid foundation for the research of group geobags. Overall, a geobag with a higher fill ratio, combined with the more flexible cloth material, was found to be the most stable. Critical Shields parameters were estimated between 0.0018 and 0.019, and the cross-sectional averaged flow velocity at incipient motion ranged from 0.49 m/s to 1.08 m/s. A shape factor was introduced to better describe the relationship between geobag characteristics and their stability on both riverbed configurations. Both the fill ratio and the bed side slope had higher importance on the geobag's stability compared to the relative depth, bag shape, and angle of flexibility. • Fill ratio affects geobag stability more than bag shape and bed configuration. • Critical Shields parameters were determined based on local shear stress. • A shape factor was proposed to better correlate bag stability to bag characteristics. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the fractional magnetohydrodynamic (MHD) flow model of a generalized second-grade fluid through a porous medium with Hall current. The fully discrete numerical scheme for solving the model is developed using the L 2 − 1 σ formula and Legendre spectral method in time and space, respectively. On the basis of sum-of-exponentials (SOE) technique, a fast L 2 − 1 σ formula for the Caputo fractional derivative is employed to reduce the computational and storage cost. The stability and convergence in L 2 -norm of the fast L 2 − 1 σ spectral scheme are proved relatively simply, with the accuracy order O (τ 2 + N − r + ε) , where τ is the time step, N is the polynomial degree and ε is the SOE tolerance error. Besides, we also consider the nonuniform meshes in time to effectively deal with the weak singularity of the solution at the initial time. Finally, theoretical analysis and the effectiveness of the fast algorithm are verified by numerical examples, the effect of various physical parameters on the fluid flow velocity is analyzed. [ABSTRACT FROM AUTHOR]

Mixing characteristics play an important role on the operational process of rotating detonation combustor (RDC). In this paper, a series of numerical calculations were conducted to analyze the influence of injection diameter, injection position, reactant mass flow rate, and equivalence ratio on mixing characteristics. Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed in detail. The findings indicated that all four injection conditions had significant influence on mixing characteristics, among which injection position was the most significant factor. When injection position was in convergent section, the mixing characteristics were better than those in ignition section. Reducing the fuel diameter gradually improved mixing characteristics, but also increased total pressure loss. The change of reactant mass flow rate had a minimal effect on mixing characteristics. As equivalence ratio decreased, mixing characteristics decreased and total pressure loss decreased. In addition, the comparative analysis also showed that penetration depth of hydrogen had an impact on flow field disturbance and distribution of return region, which led to the difference in mixing characteristics. When hydrogen was injected into the convergent structure section where air flow velocity did not reach sonic speed and was in acceleration phase, total pressure loss would be effectively reduced in combustor dome. • A new rotating detonation combustor model with convergent inlet structure was built. • Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed using RANS and LES. • Mixing characteristics of RDC were significantly enhanced when the injection position was in convergent structure section. [ABSTRACT FROM AUTHOR]

This study examines the molecules motion influences and thermal attributes in power-law non-Newtonian dissipative fluids' magnetohydrodynamic behavior, Joule heating, electromigration, and Cattaneo-Christov effects. Effects of Hall on both flow velocity and temperature, as well as the heat transport are considered. The investigation looks at heat transference that occurs when there is a slippage consequence, how the temperature influences the viscosity of the fluid, and how the potential parameters influence the exponential non-Newtonian flow of fluid via an extensible sheet. Runge-Kutta-Fehlberg's approach, which is based on the shooting procedure, was used to develop computational solutions for nonlinear ordinary differential equations. When exposed to a deformation that is generated by expansion, pressure, or agitation, a dilatant fluid is characterized by a phenomenon in which its viscosity rises and may harden. This phenomenon is referred to as the dilatation phenomenon. High shearing rates provide the impression that it is stable. When expanded, subjected to pressure, or agitated, dilatant fluids become more viscous and transform into solids. Both the non-equilibrium that occurs within the fluid and the reduction of the irreversibility processes that occur within it are caused by the acquired charges that are a result of Hall effect of fluid molecules. [ABSTRACT FROM AUTHOR]

To investigate the feasibility of obtaining black-blood imaging with a large FOV from the neck to the aortic arch at 3 T using a newly modified Relaxation-Enhanced Angiography without Contrast and Triggering for Black-Blood Imaging (REACT-BB). REACT-BB provides black-blood images by adjusting the inversion time (TI) in REACT to the null point of blood. The optimal TI for REACT-BB was investigated in 10 healthy volunteers with TI varied from 200 ms to 1400 ms. Contrast ratios were calculated between muscle and three branch arteries of the aortic arch. Additionally, a comparison between REACT-BB and MPRAGE involved evaluating the depiction of high-intensity plaques in 222 patients with stroke or transient ischemic attack. Measurements included plaque-to-muscle signal intensity ratios (PMR), plaque volumes, and carotid artery stenosis rates in 60 patients with high-intensity plaques in carotid arteries. REACT-BB with TI = 850 ms produced the black-blood image with the best contrast between blood and background tissues. REACT-BB outperformed MPRAGE in depicting high-intensity plaques in the aortic arch (55.4% vs 45.5%) and exhibited superior overall image quality in visual assessment (3.31 ± 0.70 vs 2.89 ± 0.73; p < 0.05). Although the PMR of REACT-BB was significantly lower than MPRAGE (2.227 ± 0.601 vs 2.285 ± 0.662; P < 0.05), a strong positive correlation existed between REACT-BB and MPRAGE (ρ = 0.935; P < 0.05), and all high-intensity plaques that MPRAGE detected were clearly detected by REACT-BB. REACT-BB provides black-blood images with uniformly suppressed fat and blood signals over a large FOV from the neck to the aortic arch with comparable or better high-signal plaque depiction than MPRAGE. • New flow-independent black blood imaging without respiratory triggering. • Robust and uniform blood and fat suppression over a large field of view. • Blood signal suppression unaffected by blood flow velocity or vascular anatomy. • Superior to conventional method in depicting vulnerable plaque in aortic arch. • Useful for detecting vulnerable plaques from neck to aortic arch in a short time. [ABSTRACT FROM AUTHOR]

Neurovascular coupling (NVC) represents the increase in regional blood flow associated with neural activity. The aim here was to describe a new approach to non-invasive measurement of NVC by spectral analysis of the cerebral blood flow velocity (CBFV) with transcranial Doppler. In a sample of 20 healthy participants, we monitored systolic CBFV in the left posterior cerebral artery (PCA) during off (eyes closed) and on (flickering checkerboard) periods. The contralateral middle cerebral artery was simultaneously monitored as a control. Each participant was submitted to three experiments, each having five cycles, with increasing duration of the cycles, from 10 s (0.1 Hz) to 20 s (0.05 Hz) and lastly 40 s (0.025 Hz), half the time for on and for off periods, constituting a total of 6 min. The successive cycles were expected to cause oscillation in CBFV in a sinusoidal pattern that could be characterized by spectral analysis. We also measured the classic CBFV overshoot as the relative increase in percentage of systolic CBFV from baseline. The relationship and agreement between the two methods were analyzed by linear regression and Bland–Altman plots. In every participant, a clear peak of amplitude in the PCA CBFV spectrum was discernible at 0.1, 0.05 and 0.025 Hz of visual stimulation. On average, this amplitude was 7.1 ± 2.3%, 10.9 ± 3.5% and 17.3 ± 6.5%, respectively. This response contrasted significantly with an absent peak in middle cerebral artery monitoring (p < 0.0001). The spectral amplitude and classic overshoot were highly correlated and linearly related (p < 0.0001). NVC can be quantified by the spectral amplitude of PCA CBFV at slower and higher frequencies of visual stimulation. This method represents an alternative to classic overshoot without the need for stimulus marking or synchronization. [ABSTRACT FROM AUTHOR]

• The flow characteristics of vertical slot fishways at different slopes (1.5%, 3.0%, 4.5%, 6.0%) were systematically studied. • The turbulence and energy dissipation in a fishway increase with increasing slope. • The distribution of vorticity shows little variability with increasing slope but may interfere with the passage of fish through the vertical slot. • An increase in water depth has no significant effect on the flow characteristics in the pool. The effects of a vertical slot fishway slope (with slope values from 1.5% to 6%) on a flow field are numerically investigated, using a re-normalization group k – ε model. The distribution of the velocity, turbulence kinetic energy (TKE), average energy dissipation rate per unit volume (E), and vorticity for different slopes are systemically explored. The results indicate that, with an increase in slope, the appearance of downward flow in conjunction with an increase in vertical velocity results in three-dimensional flow characteristics. The recirculation region in H s , at a 6.0% slope, was 20.9% less than that at a 1.5% slope. Meanwhile, the flow velocity in the vertical slot region grew with increasing slope, which would limit the passage of fish with burst speed lower than the velocity in the vertical slot region. The TKE and E may locally exceed the threshold at larger slopes. Furthermore, vorticity distribution shows little variability with increasing slope, but may interfere with the equilibrium of the fish in the vertical slot region. In addition, the change in water level has little effect on the flow field, which is changed by the increase in slope. These findings can aid vertical slot fishway designs especially in terms of the efficiency of fish passage. [ABSTRACT FROM AUTHOR]

This study investigates the flow and hemodynamics of small perforator blood vessels that branch from the basilar artery (BA) in the brain. Using advanced imaging techniques and computational fluid dynamics (CFD) simulations, detailed 3D geometries of the perforators were acquired through barium contrast injection, micro-CT scans, and data processing. The hybrid geometry, combining micro-CT scans and mesh extraction algorithms, provided accurate vessel models. The influence of different types of finite volume on the analysis was examined, with polyhedral elements showing the most efficient ratio of the analysis time to convergence level. Additionally, the effect of boundary conditions on hemodynamic parameters was studied. Simulations using 0.0 mmHg pressure conditions at the outlets directed flow mainly through the BA, neglecting the perforator branches. In contrast, non-zero outlet pressure conditions significantly increased the flow in the perforators, leading to non-physiological flow velocities and overestimation of hemodynamic parameters. The assumption of pressure conditions of 0 mmHg at outlets was found to be valid for simple single vessel geometries, but not for more complex vascular systems. This research contributes valuable information on the complex flow patterns and hemodynamics of small perforator blood vessels in the brain and emphasizes the importance of accurately modeling geometry and boundary conditions in such studies. [ABSTRACT FROM AUTHOR]

[Display omitted] Experiments with dilute methane–oxygen mixtures at pressures of 100–200 Torr on the flame front propagation towards the flow of combustible gas created by a fan showed that both the mean flame velocity and the length of the 'flame jump' through a hole in a flat obstacle increase with increasing counter flow velocity; i.e. , the flame accelerates towards the counter flow of combustible gas from the fan. [ABSTRACT FROM AUTHOR]

An experimental study of the effect of lowered temperatures (from 25 °C to −5 °C) on the velocity and viscosity of composite liquid fuel (CLF) flow in mini-channels was performed at low Reynolds numbers. Examined CLFs are composed of water, coking coal, and sludge from coking coal processing, mixed with lignite polymer, acidic sodium pyrophosphate, isononylphenol and a mixture of mono-and dialkylphenols with ethylene oxide. The method of adjusting the critical ratio between the Reynolds numbers at the actual liquid flow rate of the local consumer and at the pump flow rate has been developed for CLF pipeline transport in off-season and winter temperature conditions. It is based on the constant regulation of the pump flow rate, depending on the current external temperature. Under a controlled decrease in the pump flow rate and a CLF temperature of −5 °C, its transportation by pipeline was successfully performed at laboratory conditions. [Display omitted] • Low-Reynolds composite liquid fuel flow under sub-ambient temperatures is examined. • Scalable mini-channel flow optimization method is developed to transport fuel slurry. • Method is based on pump flow rate regulation considering current ambient temperature. • Fuel slurry pipeline transportation is successfully performed at −5 °C. • Fuel flow velocity and relative viscosity are determined in pipeline at −5 °С0.25 °С. [ABSTRACT FROM AUTHOR]

This work focuses on the analytical solution to the Riemann problem (RP) for a 1-D non-ideal flow of dusty gas with external force. Here it is presumed that external force is a continuous function of time. We explicitly obtain the elementary wave curves to 1-D non-ideal flow of dusty gas with external force and determine these wave curves in form of characteristics. Exhaustive calculations were performed for the elementary wave solutions, such as the rarefaction wave, shock wave, and contact discontinuity. We examine the influence of dust particles on density, velocity of flow, and shock speed and their implications on the solution of RP. Also, the implication of addition of external force is that all solutions are not self similar. [ABSTRACT FROM AUTHOR]

Post-operative brain injury in neonates may result from disturbed cerebral perfusion, but accurate peri-operative monitoring is lacking. High-frame-rate (HFR) cerebral ultrasound could visualize and quantify flow in all detectable vessels using spectral Doppler; however, automated quantification in small vessels is challenging because of low signal amplitude. We have developed an automatic envelope detection algorithm for HFR pulsed wave spectral Doppler signals, enabling neonatal brain quantitative parameter maps during and after surgery. HFR ultrasound data from high-risk neonatal surgeries were recorded with a custom HFR mode (frame rate = 1000 Hz) on a Zonare ZS3 system. A pulsed wave Doppler spectrogram was calculated for each pixel containing blood flow in the image, and spectral peak velocity was tracked using a max-likelihood estimation algorithm of signal and noise regions in the spectrogram, where the most likely cross-over point marks the blood flow velocity. The resulting peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistivity index (RI) were compared with other detection schemes, manual tracking and RIs from regular pulsed wave Doppler measurements in 10 neonates. Envelope detection was successful in both high- and low-quality arterial and venous flow spectrograms. Our technique had the lowest root mean square error for EDV, PSV and RI (0.46 cm/s, 0.53 cm/s and 0.15, respectively) when compared with manual tracking. There was good agreement between the clinical pulsed wave Doppler RI and HFR measurement with a mean difference of 0.07. The max-likelihood algorithm is a promising approach to accurate, automated cerebral blood flow monitoring with HFR imaging in neonates. [ABSTRACT FROM AUTHOR]

At high current density, the mass transfer in proton exchange membrane fuel cells (PEMFC) is significantly influenced by the flow field structure. In this paper, a bilateral track flow field (BTFF) is proposed to improve the transverse and longitudinal mass transfer as well as the water removal capacity of PEMFC. The geometry of the BTFF is optimized by orthogonal tests to obtain the optimal combination of geometric parameters and levels. Then using numerical modeling, the impact of the optimized BTFF (BT6) on the efficiency of the PEMFC was examined. The results show that BT6 significantly improves the utilization of the under-rib region by shortening the reactive gas diffusion path length to obtain a more uniform oxygen distribution, and the average oxygen concentration in the midline of the under-rib of the BT6 is increased by 102.60%, furthermore, the current density is increased by 16.32% compared with that of the parallel flow field (case0). In addition, by reducing the cross-sectional area of the gas flow channel, the BT6 has a higher gas flow velocity, which accelerates the removal of cathode liquid water, and the average liquid water saturation in the midline of the under-rib of the BT6 is reduced by 15.26% compared with case0. Finally, by analyzing the net power density of PEMFC, it can be found that the net power density of BT6 is increased by 15.68% compared with case0, which has good practical application value. • A novel bilateral track flow field is proposed and optimized by orthogonal test. • Locally improved structure enhances transverse and longitudinal mass transfer. • The average oxygen concentration under-rib of the optimized flow field has increased by 102.60%. • The optimized flow field net power density has increased by 15.68%. [ABSTRACT FROM AUTHOR]

This paper aims to numerically investigate the effects of high compression ratio (CR) on the performance of ammonia-hydrogen engines. In this work, four CRs from 10.7 to 13.7 with scanning spark timing (ST) from 28°CA to 0°CA BTDC were analyzed. The main results are as follows: As the CR increases, there is a trade-off relationship between the dissipation rate of turbulence and the turbulent kinetic energy (TKE). Initially, the TKE rises as the CR increases. As the CR continues to rise, the tendency for an increase in TKE diminishes, while the turbulent dissipation rate consistently rises. Additionally, there is an escalation in heat transfer loss. Therefore, there is a trend of rising and then falling in the flow velocity and turbulence intensity with the increase of the CR. Ammonia-hydrogen flame propagation is susceptible to temperature and flow field, and a high CR can improve ignition stability, shorten combustion duration, minimize cooling loss, and enhance output power. Unfortunately, the emission of NOx gradually rises as the CR increases. At high CR, the combustion performance is optimized by adjusting ST, and the maximum IMEP and ITE are 4 bar and 38.3 %, respectively. The ST for maximum braking torque (MBT) should be gradually delayed toward TDC as the CR increases. • As the compression ratio increases, the flow velocity first rises and then decreases. • The turbulent dissipation rate increases with increasing compression ratio. • A high compression ratio improves ignition stability and combustion velocity. • The NOx gradually increases with the increase of the compression ratio. • A high compression ratio improves the power and economy of NH3-H2 engines. [ABSTRACT FROM AUTHOR]

A CFD model coupled with population balance equations is developed to systematically study the effects of column internals on specific interfacial area generated in a pulsed sieve plate column (PSPC). The model has been validated against experimental data on holdup and Sauter mean drop diameter in laboratory scale PSPCs of different geometries. The column internals comprised of sieve plates with varying hole diameter, fractional open area and interplate spacing. Typically the standard sieve plate cartridge is characterised by sieve plates (3.2 mm diameter sieve holes with an fractional open area of 23%) placed 50 mm apart. A systematic response surface methodology has been adopted to determine the relative importance of these parameters on specific interfacial area. 3 factor 3 level Box Behnken design has been adopted. Specific interfacial area decreases with an increase in sieve hole diameter, interplate spacing and open area. Sieve hole diameter is found to be the most significant parameter affecting specific interfacial area. Important hydrodynamic variables like flow velocities in continuous and dispersed phases and how column internals affect them are also discussed. • 2D CFD-PB model of PSPC to predict specific interfacial area. • Model extensively validated against experimental data for PSPC. • Box-Behnken study to numerically study effect of internals on specific interfacial area. • Hole diameter is the most influence parameter affecting specific interfacial area. [ABSTRACT FROM AUTHOR]

Stellate ganglion block (SGB) may have protective effects in patients at risk of vasospasm following subarachnoid hemorrhage (SAH) due to reduced sympathetic activity. However, the safety and clinical outcomes of SGB in this scenario are not definitively known. The objective was to evaluate the safety, clinical outcomes, and cerebral blood flow velocity in patients submitted to SGB or cervical sympathectomy with SAH. Following Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, a systematic review and meta-analysis of studies investigating SGB or cervical sympathectomy use in SAH were conducted. PubMed, Cochrane Library, and Embase were evaluated. Patients with mRS from 0 to 2, GOS from 4 to 5, or symptom resolution were considered favorable clinical outcomes. Related mortality was defined as death by vasospasm or delayed cerebral ischemia. The analysis included 8 studies comprising 182 patients. Only 2 studies employed SGB prophylactically. The results revealed favorable outcomes in 52% of patients (95% CI: 37%–65%). The overall incidence of complications was 2% (95% CI: 0% –26%). The mortality rate was 13% (95% CI: 7%–21%), with a vasospasm-related mortality rate of 11% (95% CI: 2%–20%). A decrease of cerebral blood flow velocity was reported in 4 studies. The notable reduction in cerebral blood flow velocity following SGB, alongside positive outcomes and a low occurrence of mortality and complications, highlights its significance as a therapeutic intervention for vasospasm following SAH. While the number of studies evaluating SGB as a preventive measure is limited, the promising results emphasize the importance of future research. [ABSTRACT FROM AUTHOR]

This work presents the results of two-dimensional numerical simulation of processes, arising from the interaction of an incoming flow of a well-mixed stoichiometric hydrogen-air mixture with a wedge in a bounded region at high Mach velocities using Navier-Stokes type equations taking into account chemical interactions. The Mach number of the incoming flow from 9 to 12 were considered. Various wave configurations were obtained depending on the velocity of the incoming flow. For the flow Mach number of 9, the presence of a detonation wave perpendicular to the flow was obtained. For high flow velocities, another similar wave configuration of the same type was obtained. • A simulation of a flow interaction with a wedge at high Mach speeds was carried out • A well-mixed stoichiometric hydrogen-air mixture was considered • Hong's kinetic mechanism was considered • Two wave configurations were obtained depending on the velocity of the flow • For Mach number equal 9 the detonation wave perpendicular to the flow was obtained [ABSTRACT FROM AUTHOR]

Children with moyamoya are at high risk for incident and recurrent stroke. Transcranial Doppler (TCD) ultrasound is an attractive option to screen high-risk populations for moyamoya and to provide stroke risk stratification information due to its safety and cost-effectiveness. We used TCD to evaluate cerebral blood flow velocities in children with presurgical moyamoya and to determine if velocities differ between children with stable and unstable disease. Fourteen participants aged ≤21 years with a radiographic diagnosis of moyamoya or moyamoya-like arteriopathy underwent a research TCD at a median age of 7.2 years. TCDs were performed outside of the setting of acute stroke and before surgical revascularization. Arteriopathy was classified as unstable if the participant had a stroke or transient ischemic attack within three months preceding the TCD. Middle cerebral artery and internal carotid artery (ICA) blood flow velocities were elevated. The median M1 velocity was 138 cm/s (interquartile range [IQR] 106 to 168). Individual M1 flow velocities were a median of 5.0 S.D.s above age-based normative values. The median distal ICA velocity was 146 cm/s (IQR 124 to 163). Individual ICA flow velocities were a median of 5.9 S.D.s above normative values. Participants with unstable arteriopathy had higher M1 velocities compared with those with stable arteriopathy (170 vs 119 cm/s, P = 0.0003). We did not identify velocity differences based on comorbid conditions or age. These preliminary data suggest that TCD is a promising tool for screening for cerebral arteriopathies in high-risk pediatric populations and assessment for unstable disease. [ABSTRACT FROM AUTHOR]

Hydraulic erosion technology (HET) is a method of injecting a large amount of water into a blocked fracture to enhance its permeability. However, the incipient motion characteristics of the deposited particles in a fracture during hydraulic erosion are still unclear. This study conducted particle incipient motion experiments under the hydraulic conditions in a fracture, and investigated the particle incipient motion behavior and the variation in the characteristics of the threshold flow velocity with a change in the particle diameter. In addition, a new formula was developed to predict the threshold flow velocity of the deposited particle in the fracture, and the effects of fluid density, viscosity, and viscous sub-layer thickness on the threshold flow velocity were discussed. Furthermore, a method for optimizing the process parameters of HET was proposed. Results revealed that hydraulic erosion causes three particle motion states and four particle motion behavior in fractures. In addition, with an increase in the particle diameter, the threshold flow velocity first decreased and then increased. Further, increasing the fluid density and reducing the fluid viscosity were observed as two effective means for reducing the threshold flow velocity in fractures. Furthermore, an increasing fluid density was more sensitive to a reduction in the threshold velocity in fractures. These findings are expected to guide the optimization of the process parameters of HET. [Display omitted] [ABSTRACT FROM AUTHOR]

The hemispheric differences in the impact of the geomagnetic storms of June 2015 and December 2015 are investigated. A meridional chain of ground observatories along 95°E ± 10°E (conjugate point-GNSS receiver/Ionosonde), satellite in-situ measurements (SWARM/COSMIC/C-NOFS), and Total Electron Content maps are utilized. Symmetric negative (positive) effects were noted during the main phase of the June (December) storm but hemispheric asymmetry was manifested during the recovery phase. The quiet time hemispheric asymmetry was reversed during both storms with positive TEC effects on the winter side. Differential VTEC and NmF2 responses exhibited seasonal variation. On 23 June 2015, the VTEC enhancements in the southern low latitude were large and consistent in contrast to the weak response in NmF2. In contrast, during the December storm, the NmF2 depletion in southern low latitude was more severe than the corresponding depletion in VTEC. The topside density/TEC enhancement in the southern low latitude recorded by SWARM was much higher than 300 % during the morning of 23 June. The SWARM Ne/TEC profile as well as the ground GPS TEC map showed a third latitudinal maximum around −45° dip angle of field lines in southern low latitudes on 23 June, in addition to the conventional EIA crests. Similarly, an early morning maximum was recorded at + 45° dip (northern hemisphere) on 21 December. The hmF2 measured by the southern hemisphere ionosonde and COSMIC satellite showed an anomalously higher altitude of the F2-layer on 23 June while C/NOFS recorded equator-ward meridional flow velocity. The reversal of the hemispheric asymmetry and the additional storm time transient maximum on the winter side is attributed to the equator-ward winds surge in the winter hemisphere due to storm time heating of the polar region. [ABSTRACT FROM AUTHOR]

With green energy advancing, the demand of high-sensitive hydrogen sensor is strongly urgent for wide demanding applications, such as energy storage, leak detection, and chemical production. The utilization of resistive hydrogen sensors has brought revolutionary developments for the field of high-performance devices. Regrettably, design and optimization of the hydrogen sensor structure for response enhancement seems to have been overlooked. In this study, we design and manufacture a bionic tridimensional stereoscopic hydrogen sensor (TSHS) based on topology optimization reinforced by artificial neural network, subjected to gas flow. Measurement and observation of TSHS at room temperature demonstrates a 3-times higher flow velocity when compared with the Spiral-serpentine array and the tolerance between simulation and experiment is less than 1 % under the same conditions. Base on theoretical investigation and test validation, the TSHS, which causes itself to favorably stable and exceptional electrical performances at ultralow hydrogen concentration, opening up plenty of opportunities for high-efficiency detection sensors as well as allows for topology optimization in gas detection, early warning equipment and biosensor. • Topology optimize iterative evolution for stereoscopic hydrogen sensor. • Circular tridimensional stereoscopic sensor primitive for performance improvement. • Artificial neural network optimize for tridimensional stereoscopic pixel topology. • Experimental results validates the accuracy of the calculation results. [ABSTRACT FROM AUTHOR]

Using local slurry laminar flow to align alumina platelet in the slurry and fabricate textured alumina by ceramic stereolithography has been shown with potential. However, the alignment process of alumina platelet and the corresponding texturing of alumina based on this method have not yet been revealed. This study systematically analyzed the mechanism of aligning alumina platelet in the local flow and the evolution of the microstructure of textured grain. The results showed that with the increase of the alumina platelet content in the slurry, the thickness of the grains gradually decreased. After sintering at 1600 °C for 2 h, textured alumina had mainly the crystal plane of (1010). The textured alumina with 15 vol% alumina platelet addition had the highest Lotgering factor (65 %) of (1010). The alumina platelet located in the middle and bottom of the local flow field aligned slower during the flow process. The distribution of flow velocity gradient was the main factor determining the alignment of alumina platelet. [ABSTRACT FROM AUTHOR]

A Pt–Co/Al 2 O 3 bimetallic catalyst for catalytic hydrogen combustion (CHC) is prepared and its performance is evaluated. A colloidal dispersion of a Pt-sulphite complex is used as the Pt precursor instead of the conventional H 2 PtCl 6 solution. The prepared catalyst maintains its catalytic activity at a temperature of up to 337 °C for 500 h of continuous CHC. To assess the catalytic activity and thermal conductivity of the catalyst, a catalytic cartridge for a recombiner section is designed. The thermal distribution over the catalytic surface during CHC is measured, using an infrared camera, as a function of inlet hydrogen concentration (0–10 vol%) and gas flow velocity (4–12 m/s). Hydrogen conversion is also determined, to evaluate the catalytic activity of the prepared catalysts. Results of this study indicate that the Pt reactive metal can be partially replaced with Co—thus reducing the cost of the catalyst, without diminishing the catalyst performance towards CHC. [Display omitted] • Reactive Pt–Co bimetallic catalyst was prepared for catalytic hydrogen combustion. • Pt colloidal dispersion resulted in deposition of Pt particles of 1.2 nm in size. • The maximum conversion of 86% was obtained for Pt–Co catalyst. • No decrease in catalytic activity after 500 h of hydrogen combustion at >270 °C. • Co metal demonstrated low performance even at temperatures as low as 80 °C. [ABSTRACT FROM AUTHOR]

Mixing in the combustion chamber is influenced by the velocity distribution of the inlet airflow. Numerical simulations are carried out by using the 3D coupled implicit Reynolds-averaged Navier-Stokes (RANS) equations and the SST k-ω turbulence model. This article compares the flow field characteristics of non-uniform flows with uniform flows. The results show that the penetration depth increases by 22% in the case of a decreasing velocity distribution along the longitudinal direction compared to the increasing velocity condition. The difference in total pressure loss compared to uniform flow is greater than 4%. The mixing coefficient in the cavity is only 81% of uniform flow. The two-hole jet flow approach is able to rapidly reach 90%. The study shows that the non-uniform inlet has a considerable impact on fuel mixing. The high velocity region near the jet hole contributes to the mixing performance of the engine combustion chamber. • A numerical study of the mixing mechanism in supersonic non-uniform flow. • The effects of different flow on the mixing characteristics. • The high-speed region is distributed near the jet is helpful for mixing. • The high velocity flow close to the jet causes the local flow to lift much higher. [ABSTRACT FROM AUTHOR]

Agglomeration of fine particles is an essential procedure to improve separation efficiency of dust-removal devices. This paper focuses on the treatment of biomass Micro-Nano particles using cascade electrostatic and magnetic fields. A carefully designed wind tunnel is built to investigate the agglomeration performance of pre-charged Micron-Nano particles (0.016–9.84 µm) in uniform magnetic field. The influence of supply voltage (10–30 kV) in the electrostatic unit and the bulk flow velocity (1–5 m/s) across the device upon agglomeration is studied. The results indicated noticeable agglomeration behavior because of reduced submicron particles and increased larger particles. Strengthening Supply voltage input has a positive yet minimum effect on the overall agglomeration efficiency. Effect of bulk flow velocity on agglomeration is remarkable due to magnetic field. Therefore, agglomeration of pre-charged particles in uniform magnetic field is dominated by Lorentz effect and stream-wise spacing of the device. This work provides a reference for further computational attempt in the future. [Display omitted] • Agglomeration of biomass Micro-Nano particles can be realized with proposed method. • Supply voltage of the electrostatic unit has minimum influence upon agglomeration. • Effect of bulk flow velocity on agglomeration is remarkable due to magnetic field. [ABSTRACT FROM AUTHOR]

Ice slurry is broadly used as the medium for refrigerating medium, which can effectively reduce energy consumption. However, the change of ice particle size makes the flow properties of ice slurry more complicated, which limits its application in cooling system. A coupled model combining CFD and PBM techniques is developed in this article to effectively depict the variations in ice particle size and the flow of ice slurry. Based on this model, the flow properties of ice slurry isothermally in horizontally placed straight and U-shaped pipes are studied. It is found that velocity determines the degree of agglomeration and fragmentation of particles. The particle fragmentation effect is enhanced and the particle size is reduced as the flow velocity increases, which promotes the homogeneous particle distribution. With increasing the ice content, the size of particles and particle agglomeration increases. And the ice particle size presents a symmetrical distribution. The larger the initial average particle size, the weaker the agglomeration effect, and conversely the weaker the fragmentation effect. In the bending section of the U-shaped tube, the agglomeration effect between particles becomes stronger as the flow velocity decreases and the ice volume and curvature ratio increase. • A CFD-PBM coupled model is developed suitable for describing ice slurry flow. • The agglomeration efficiency is introduced in agglomeration kernel model. • The impact of ice particle size evolution on ice slurry flow behavior is analyzed. • The ice particle size evolution in U-shaped tubes is studied. [ABSTRACT FROM AUTHOR]

The gas-liquid flow regimes transition mechanism and bubble behavior in gas-liquid two-phase impinging jet reactor are studied by numerical method. The liquid phase velocity, gas-liquid flow regimes, bubble behavior in the impinging reactor under different gas and liquid velocities are analyzed to explore. The vortex in flow field changes periodically, and the period is 7.5 s. According to the dispersion mode of bubbles in the reactor, the gas-liquid flow regimes can be divided into three regimes: cluster upflow, gradual dispersion and complete dispersion. The critical condition equations of flow regimes transition are established combination of Flow number (Fl) and Froude number (Fr). The distribution range of bubble diameter in the reactor increases with the increase of gas velocity and decreases with the increase of liquid velocity. The turbulent kinetic energy, turbulent dissipation rate and the velocity in the flow field are gradually weakens from the impact center to the radial direction. Based on dimensionless analysis, the mathematical model of bubble Sauter diameter is established to predict bubble Sauter diameter accurately. This research provides a theoretical basis for the amplification and optimization of reactors. [Display omitted] • The gas-liquid two-phase impinging jet reactor was designed by combining bubbly jet and impinging stream. • Flow regimes in gas-liquid two-phase impinging jet reactor were divided by the bubbly jet motion behavior. • The critical condition equations of flow regimes transition were established combination of Flow number and Froude number. • The dimensionless model was provided to predict bubble Sauter diameter. [ABSTRACT FROM AUTHOR]

Electrodialysis (ED) is more robust than reverse osmosis in terms of scaling, purity, and control, but its efficiency is dependent on concentration polarization. Concentration polarization is not only inherent in ED, but also commonly found in microfiltration, ultrafiltration, nanofiltration, reverse osmosis, and fuel cells with ion exchange membranes (IEMs). The current meta-synthesis review aims to identify the best approach for reducing concentration polarization, increasing velocity, or maximizing spacer design. Concentration polarization can significantly impact membrane capability and reduce overall performance. To reduce concentration polarization, innovative geometries and configurations of membrane spacers are needed. Carefully designed spacers that increase channel turbulence can help mitigate concentration polarization effects. However, advanced spacers still have negative consequences, such as the shadow effect, which reduces the ion exchange area and increases permeation resistance. Increasing the flowrate can improve membrane performance, maximize recovery/permeate rate, and reduce the limitations of spacer design. However, increasing the flowrate can have drawbacks in certain membrane applications. For example, a higher Reynolds number may improve spacer performance with a higher Sherwood number but at the cost of a greater power number. This review found that the extent of concentration polarization formation is heavily influenced by both spacer design and solution velocity. Convective motions affect mixing, making the concentration domain within the cell highly dependent on spacer design and flow velocity. [Display omitted] • Concentration polarization forms a thin diffusion boundary film along IEMs. • Improved spacers still increase flow resistance compared to a spacer-less channel. • Raising flowrate occurs at the price of an increase in electrical power consumption. • Concentration polarization is reduced by enhanced spacer and increased flowrate. • An enhanced spacer supports improved mixing particularly at greater Reynolds numbers. [ABSTRACT FROM AUTHOR]

A diffused aeration system in an activated sludge process is generally designed based on a limited number of typical diffuser patterns. There are instances where these patterns have shown various operational and process issues, resulting in poor process performance. To address these issues, bubble interactions and the mixing conditions must be factored into the design of alternative patterns. For this purpose, a validated full-scale CFD model was used to simulate five diffuser patterns: lateral, grid, line, stripe, and checkered patterns‎, the first two in operation, and the next three as designed patterns. The patterns were simulated for an aeration tank under identical functional conditions. The population balance method was incorporated into the model to analyze how various patterns affect bubble size distribution. It was found that changing the pattern of diffusers had a significant effect on bubble breakup/coalescence and the resulting bubble size distribution. The results showed a range of 6.1–22.9% for the coarse bubble percentage and 11.9–16% for the fine bubble percentage in the five simulated patterns. Moreover, evaluating flow circulation and velocity based on the average flow velocity data of the simulated patterns showed up to 30% variation, ranging from 0.29 to 0.375 m/s. It highlighted the great impact of diffuser patterns on bubble size and mixing quality as notable factors in oxygen transfer efficiency. Finally, the proposed patterns were compared and ranked based on air distribution, bubble size, and mixing quality criteria using the multi-criteria decision-making (MCDM) approach. It was concluded that the checkered pattern outperformed the proposed and existing ones. [ABSTRACT FROM AUTHOR]

This study explores the effect of silver nanoparticles on heat transfer and flow behavior within the context of the Ellis fluid model. It specifically considers electroosmotic forces in a nonuniform divergent channel with compliant walls. The analysis involves studying thermal transport in silver-blood nanofluid flow, using MATHEMATICA 13.2 software to obtain exact solutions for velocity and temperature distribution. Findings reveal that certain parameters, such as wall damping and wall elastic properties, increase skin friction, while compliant wall parameters generally reduce flow velocity. Additionally, wall rigidity and tension parameters lead to larger trapped boluses. Notably, a 1% concentration of nanoparticles enhances heat transfer by up to 13.75%, offering control over heat transfer rates. This research introduces a novel perspective by examining compliant wall impacts on heat transfer analysis in the context of electroosmotic flow within the Ellis fluid model, incorporating silver nanoparticles with potential therapeutic applications due to their antibacterial properties. [ABSTRACT FROM AUTHOR]

A new abrasive flow polishing method with a ferromagnetic blockage placed inside tube was proposed for finishing internal surface of slender tubes with varying diameters. A mathematic model was established to calculate the blockage's profile. Results indicate that the special designed ferromagnetic blockage provides an effective tool to adjust the flow velocity and pressure, and thus controlling local material removal. Axial tool marks were removed by rotating the workpiece during polishing. A uniform internal surface (Sa < 40 nm) was achieved when finishing a puncture needle with diameters ranging from 0.3 to 0.7 mm (initial Sa 600 - 1200 nm). [ABSTRACT FROM AUTHOR]

Unionid populations are declining worldwide as they are threatened by anthropogenic habitat alterations, the introduction of invasive alien species and the effects of climate change. Several studies have focused on the habitat preferences of adult mussels but none to date have reported on the importance of the habitat preferences of host fish species. The aim of this study was to determine the habitat preferences of unionid host fish species in the Netherlands, to examine potential differences between native and alien host fish species, and to evaluate the effect of alien host fish species on unionid dispersal. Species sensitivity distributions (SSDs) were constructed for the range of occurrences and laboratory tolerance of host fish species in the Netherlands for water temperature, substrate type, flow velocity, and water depth. A case study was selected to assess the suitability to substrate type, flow velocity and water depth of a novel river habitat along longitudinal training dams in the river Waal. Unionid host fish species in the Netherlands preferred shallow littoral zones (0.1 m) with low flow velocity (0.05 m/s), an average water temperature of the Rhine delta (15°C), and most substrate types (ranging from silt to cobbles). Boulder substrate was the most limiting factor of the abiotic factors assessed for both native and alien host fish species. Management options for unionid populations should include host fish species in their assessments while focusing on creating and maintaining areas with limited boulders and implementing alien host fish species removal measures. [ABSTRACT FROM AUTHOR]

One significance of the fluid flow in a curved channel is the generation of centrifugal forces. However, nothing is known on the hydrodynamic study of a couple stress fluid flowing in a porous curved channel. The proposed work, concerns with the flow of couple stress fluid in a porous curved channel and analysing the generating centrifugal force. Here, the flow of fluid in the porous curved channel takes place due to the constant pressure gradient. In this work, the effect of the radius of curvature and permeability parameters are examined on the flow velocity and temperature profiles of the considered fluid. The aim of this study is to analyse the flow pattern of the couple stress fluid, measure the rate of heat transfer, and volumetric flow rate, when fluid flow through porous curved channel. The proposed model is useful in the biofluid mechanics, nuclear reactors, and in oil and chemical industries. The present model, i.e., the flow of couple stress fluid in a porous curved channel, governs by the highly non-linear coupled differential equations which are solved by using Homotopy Analysis Method (HAM). Through this work, it is concluded that couple stress fluid's velocity and temperature is smaller in magnitude than that of the Newtonian fluid. Further, it is noticed that the fluid's flow velocity and temperature in porous curved channel is reduced significantly on increasing the curvature parameter, permeability parameter, and on reducing the couple stress parameter. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the feasibility and imaging options of contrast-enhanced volumetric ultrasound kidney vasculature imaging in a porcine model using a prototype sparse spiral array. Transcutaneous freehand in vivo imaging of two healthy porcine kidneys was performed according to three protocols with different microbubble concentrations and transmission sequences. Combining high-frame-rate transmission sequences with our previously described spatial coherence beamformer, we determined the ability to produce detailed volumetric images of the vasculature. We also determined power, color and spectral Doppler, as well as super-resolved microvasculature in a volume. The results were compared against a clinical 2-D ultrasound machine. Three-dimensional visualization of the kidney vasculature structure and blood flow was possible with our method. Good structural agreement was found between the visualized vasculature structure and the 2-D reference. Microvasculature patterns in the kidney cortex were visible with super-resolution processing. Blood flow velocity estimations were within a physiological range and pattern, also in agreement with the 2-D reference results. Volumetric imaging of the kidney vasculature was possible using a prototype sparse spiral array. Reliable structural and temporal information could be extracted from these imaging results. [ABSTRACT FROM AUTHOR]

The mass transfer efficiency of reaction gas in proton exchange membrane fuel cells (PEMFC) has a great impact on its performance, and the flow field is another important factor affecting the mass transfer performance. A kind of twisted parallel flow field (TPFF) with parallelogram equal cross-sectional area and gradually changing shape along the gas flow direction is presented in this paper. The position of each vertex of a parallelogram changes as a sinusoidal function along the flow direction. The output power density, oxygen concentration, current density, gas flow velocity, and water saturation were compared between TPFF and conventional parallel flow field (CPFF). According to the research results, the gas flow velocity of TPFF is greater than that of CPFF at Channel-GDL interface, the channel is higher than that of the CPFF, which can effectively alleviate flooding. Oxygen is more easily diffused from the bulk phase to the membrane electrode due to the decrease of the mass transfer impedance of oxygen in the TPFF. The oxygen content in membrane electrode is higher than CPFF when the fuel cell operates in the diffusion-polarized zone. Compared with the CPFF, the TPFF fuel cell has better output performance, and the maximum output power is increased by 8%. In addition, due to increasing oxygen transmission efficiency, the uniformity of the reaction is enhanced, so that the low current density region is controlled and the uniformity is improved. • A kind of twisted parallel flow field (TPFF) with changed shape and unchanged cross-sectional area is proposed. • The output power for TPFF is increased by 8% than that of the conventional parallel flow field (CPFF). • TPFF exhibit the outstanding uniformed current density and the lower risk of flooding. [ABSTRACT FROM AUTHOR]

The developed research presents a novel experimental study of the cost-effective MgO-Al 2 O 3 , MgO-CaZrO 3 perovskite, and thermally stable YSZ ceramic composites for DBD plasma actuators in aerospace applications. This study focuses on the implementation of ceramic DBD plasma actuators for aerodynamic flow control and ice creation mitigation. For this purpose, electrical power consumption analysis, induced flow velocities assessment, and mechanical and thermal characterization were performed. MgO-Al 2 O 3 presented higher induced velocities than its zirconia-based counterparts of up to 3.3 m/s, and lower heat dissipation, achieving a ceiling temperature of 46 ºC, being thereby the best-suited candidate for active flow control mechanisms. In contrast, YSZ had very high-power consumption translated into a maximum surface temperature of 155.4 ºC, establishing itself for ice mitigation. This extensive research evinces that the strategic combination of the developed ceramics' thermomechanical, thermoelectric, and electromechanical properties allows them to be a promising breakthrough material for DBD plasma actuators. [ABSTRACT FROM AUTHOR]

Erosion-corrosion resistance is a critical factor in the service life extension of metallic structural materials in front of complex flow and solid impingement. To improve the erosion-corrosion resistance, a CrN/Cr gradient coating was fabricated on carbon steel by the double glow plasma alloying technique. The CrN/Cr gradient coating mainly consists of the CrN phase and (Fe, Cr) metal phase. Debye rings from the X-ray pattern illustrated that the coating was under a compressive stress of 868 MPa. Residual stress and fine toughness of the gradient structure enhanced its adhesion strength, endowing it with the potential to accommodate strains caused by external forces. The potentiodynamic polarization test illustrated that the addition of solid particles and the increase in flow velocity severely weakened the protective ability. The mass loss rate results illustrated that the synergistic effect made the greatest contribution to the erosion-corrosion damage of the CrN/Cr gradient coating, while its proportion increased as the flow velocity increased. Compared to the substrate, the gradient structure of the coating facilitated interruption of the sharp interfaces, thereby reducing the deformation mismatch and enhancing the damage tolerance of the coating. [ABSTRACT FROM AUTHOR]

Alkaline water electrolyzer (AWE) with KOH aqueous solution as electrolyte is one of the most mature routes for green hydrogen production, in which spherical concave-convex (SCC) shaped flow fields are widely applied. However, while the addition of SCC is known to have significant effects on complex two-phase flow, in particular on the generated hydrogen, detailed understandings of the flow distributions are still lacking. In this paper, we propose to demonstrate the three-dimensional (3D) two-phase flow distributions in SCC shaped flow field for AWE by COMSOL simulation method. First, the typical geometric model is extracted from the practical AWE, based on which the mesh model is constructed; Moreover, the basic 3D simulation results of channel without SCC are evaluated by comparing with the previous experimental studies to demonstrate the model validation; Finally, the 3D flow velocity and hydrogen fraction distributions are carefully illustrated that the SCC shaped structure averages the distribution in the channel effectively and the hydrogen concentration on the electrode surface are reduced, beneficial to the improvement of the electrolysis efficiency, at the outlet of the channel, half of the geometric height (z = 4 mm), the hydrogen fraction in the straight channel is less than 3%, while the hydrogen fraction at the outlet of the SCC channel is about 4%, or even 5% locally. We believe this work can not only provide a guideline for the 3D model establishment for two-phase flow in AWE, but give detailed hydrogen distribution understandings in varied conditions with different current densities. • The 3D simulation model for two-phase flow is extracted and constructed. • The 3D flow velocity and hydrogen fraction distributions are illustrated. • The hydrogen concentration on the electrode surface is reduced by SCC structure. [ABSTRACT FROM AUTHOR]