Volumetric Flow Research Articles

Wave-powered water pump for upwelling in aquaculture: Numerical model and ocean test

Wave-powered upwelling can increase the productivity and survivability of several aquaculture species. This enhancement is due to transporting cold, nutrient-rich ocean water, typically found lower in the water column, to the surface. Macroalgaes, like kelp, exhibit increased growth from these altered conditions.The University of New Hampshire’s (UNH) wave-powered water pump (wave pump) is a point absorber wave energy converter (WEC) that uses ocean waves to create relative motion between a spar buoy and a concentric float which drives an internal pump. A numerical model of the wave pump was developed using WEC-Sim to predict device performance in the ocean. Wave pump performance was evaluated during a five day ocean test near Appledore Island in Maine in March 2023, where volumetric flow rate, relative distance between spar and float, and wave conditions were measured. These data were then used for numerical model validation.The ocean deployment recorded the device’s performance in a variety of sea states, with average significant wave heights up to 0.7 m. The ocean test data were compared to the WEC-Sim numerical model of the device with favorable results. Average values of device stroke period, stroke height, and flow rate agreed between the ocean test and model data to within approximately 16 to 22%. The validated numerical model provides a valuable tool for improving the design and developing a commercial-scale, wave-powered water pump for use in aquaculture.

Reduced fetal ductus venosus shunt fraction is associated with adverse perinatal outcomes in pregnancy with pregestational diabetes mellitus.

We aimed to determine fetal liver perfusion in PGDM and GDM pregnancies and to assess the relation of ductus venosus (DV) shunt fraction with adverse pregnancy outcomes. We conducted a prospective longitudinal observational study including 188 pregnant women: group I-patients with pregestational DM (PGDM, n = 86), group II-patients with gestational DM (GDM, n = 44), group III-control (n = 58). The patients included in the study underwent ultrasound examination at 30+0-40+0weeks of pregnancy. We evaluated volumetric blood flow adjusted to EFW (Q, ml/min/kg) for umbilical vein, DV, left and main portal vein. The relative risk was calculated for adverse pregnancy outcomes. In PGDM pregnancies, umbilical blood flow was redistributed to the fetal liver, increasing left portal and total liver volumetric blood flow (p < 0.001) compared with GDM and control groups. Pathological reduction in the DV shunt fraction (≤ 16.5%) was associated with an increased relative risk of preterm delivery (3.61 [95%CI 1.68; 7.71]), LGA-birth (1.64 [95% CI 1.26; 2.12]), neonatal adiposity (1.53 [95%CI 1.18; 1.98]), fetal hypoxia (3.47 [95%CI 1.34; 9.05]), emergency cesarean Sect.(1.93 [95%CI 1.26; 2.97]), and neonatal intensive care unit stay of more than 5days (1.78 [95%CI 1.08; 2.93]). Decreased DV shunt fraction reflects changes in fetal hemodynamics in PGDM-pregnancies and associated with an increased risk of adverse perinatal outcomes.

Numerical Analyses of Entropy Production and Thermodynamics Exergy on a Hydrogen-Fueled Micro Combustor Featuring a Diamond-Shaped Bifurcated Inner-Tube Structure for Thermophotovoltaic Applications

To improve the heat transfer mechanisms from the thermal energy to the walls, the current work presents a new structure for a micro combustor fueled by hydrogen featuring a diamond-shaped bifurcated inner-tube configuration. For this purpose, a series of three-dimensional (3D) numerical analyses are conducted to investigate the effects of the length of the diamond-shaped structure, width of inner flame channels, inlet equivalence ratio, and hydrogen volume flow rate on the key performance and thermodynamic parameters. In comparison to the conventional design, the outcomes reveal that the proposed configuration exhibits remarkable improvements in energy conversion efficiency, as it reduces the mean exhaust gas temperature by 585.98 K and boosts the exergy and radiation efficiencies by 7.78% and 14.08%, respectively. The parametric study of the design parameters indicates that elongating the diamond-shaped structure and widening the inner flame channels enhance the thermal dynamics and consequently improve the rates of heat absorption by the walls. The increase in the hydrogen volume flow rates feeds the system with additional energy and, therefore, advances the average wall temperature and its uniformity across the external surface. Nevertheless, it also reduces system efficiency due to the limited capacity of the micro combustor to utilize a large energy input along with the high magnitude of entropy production resulting particularly from the mechanism of chemical entropy generation. Operating under a stoichiometric condition balances hydrogen and oxygen in the premixed charge, achieving optimal thermal performance for the micro combustor.

The radial spreading of volcanic umbrella clouds deduced from satellite measurements

Analysis of thermal infrared satellite measurements of umbrella clouds generated by volcanic eruptions suggests that asymptotic gravity current models of the temporal (t) radial (r) spreading (r ~tf, f &lt; 1) of the umbrella-shaped intrusion do not adequately explain the observations. Umbrella clouds from 13 volcanic eruptions are studied using satellite data that have spatial resolutions of ~4–25 km2 and temporal resolutions of 1–60 minutes. The umbrella cloud morphology is evaluated using digital image processing tools in a Lagrangian frame of reference. At the onset of neutral buoyancy, the radial spreading is better explained by a stronger dependence on time of r ~ t, rather than t2/3, t3/4, or t2/9. This flow regime exists on the order of minutes and has not been observed previously in satellite data. This may be of significance as it provides a means to rapidly (within the first 2–3 observations) determine the volumetric eruption rate. A hyperbolic tangent model, r ~ tanh(t) is presented that matches the entire radial spreading time history and has a conserved torus-shaped volume in which the intrusion depth is proportional to sech(t). This model also predicts the observed radial velocities. The data and the model estimates of the volumetric flow rate for the 15 January 2022 Hunga eruption are found to be 3.6–5 × 1011 m3s−1, the largest ever measured.

Large-eddy simulations of conical hypersonic turbulent boundary layers over cooled walls via volumetric rescaling method

Large-eddy simulations (LES) of a hypersonic boundary layer on a $7^\circ$ -half-angle cone are performed to investigate the effects of highly cooled walls (wall-to-recovery temperature ratio of $T_w / T_r \sim 0.1$ ) on fully developed turbulence and to validate a newly developed rescaling method based on volumetric flow extraction. Two Reynolds numbers are considered, $Re_m = 4.1 \times 10^6\ \text {m}^{-1}$ and $6.4 \times 10^6\ \text {m}^{-1}$ , at free-stream Mach numbers of $M_\infty = 7.4$ . A comparison with a reference laminar-to-turbulent simulation, capturing the full history of the transitional flow dynamics, reveals that the volumetric rescaling method can generate a synthetic turbulent inflow that preserves the structure of the fluctuations. Equilibrium conditions are recovered after approximately 40 inlet boundary layer thicknesses. Numerical trials show that a longer streamwise extent of the rescaling box increases numerical stability. Analyses of turbulent statistics and flow visualizations reveal strong pressure oscillations, up to $50\,\%$ of local mean pressure near the wall, and two-dimensional longitudinal wave structures resembling second-mode waves, with wavelengths up to 50 % of the boundary layer thickness, and convective Mach numbers of $M_c \simeq 4.5$ . It is shown that their quasi-periodic recurrence in the flow is not an artefact of the rescaling method. Strong and localized temperature fluctuations and spikes in the wall-heat flux are associated with such waves. Very high values of temperature variance near the wall result in oscillations of the wall-heat flux exceeding its average. Instances of near-wall temperature falling below the imposed wall temperature of $T_w=300$ K result in pockets of instantaneous heat flux oriented against the statistical mean direction.

Reactive species emission characteristics of a cold atmospheric pressure plasma source for biomedical applications operated in a test chamber

This study investigates the potentials and limitations of a novel methodology to characterize the reactive species emission dynamics of cold atmospheric plasma sources for biomedical applications. The time-resolved concentrations of ozone and nitrogen oxides during operation of a modified medical device are sampled in a test chamber environment equipped with a stirring fan for effective mixing of species. The interpretation of experimental data is supported by results from a numerical model solving the diffusion-convection equation. From the linear profiles of O3 and NO2 concentrations, emission rates of 1.3−6.4 μgs-1 for O3 and 0.07-0.1μgs-1 for NO2, depending primarily on plasma input power and fan volume flow rate, were determined for the plasma source. The conversion of these rates into geometry-specific source terms for use in the numerical model led to excellent agreement between experimental and numerical results thus validating the methodology. Finally, empirical equations describing the ozone emission rate dependence on the air flow velocity are presented. The outcomes of this study may stimulate new strategies for assessment of health risks associated with reactive species emission by medical devices based on cold plasma technology.Graphic

Examining the impact of Ag-decorated CuO-H2O nanofluid on pressure and thermal efficiency in a channel with metal foam heat sinks: an experimental study

ABSTRACT In this study, nanofluids were produced from CuO nanoparticles decorated with Ag atoms at different mass concentrations, and their cooling performance was examined in a channel containing metal foam heat sinks (MFHS) with pore densities of 10 and 40 pore per inch (PPI). CuO-H2O/2% Polyethylene Imine (PEI) nanofluid with a concentration of 0.1% by mass was used. The surfaces of the CuO nanoparticles were decorated with Ag at mass concentrations of 0.03%, 0.05%, and 0.1%. Experiments were performed for volumetric flow rates varying from 17.6 L/h to 76.5 L/h in laminar conditions, and the heat fluxes applied to the bottom of the channel were chosen in the range of 3267 W/m2-5400 W/m2. The base fluid (BF)-empty surface case was used as the reference for all measurements. In the findings of experiments conducted on the base surface, it was found that decorating CuO nanoparticles with 0.03% and 0.05% Ag atoms effectively lowers the surface temperatures compared to the BF. On the contrary, an increase in surface temperatures was detected when 0.1% Ag atoms were used. Passing a 0.1% CuO-0.05% Ag/2% PEI-H2O (NF3) nanofluid through 40 PPI MFHS’ achieved the highest improvement in mean surface temperatures, with a 37.4% increase compared to using the BF on the empty surface.

Simultaneous Luminal and Hemodynamic Evaluation of the Cervical Arteries Using Nonenhanced 3D Quantitative Quiescent-Interval Slice-Selective Magnetic Resonance Angiography.

Luminal and hemodynamic evaluations of the cervical arteries inform the diagnosis and management of patients with cervical arterial disease. To demonstrate a 3D nonenhanced quantitative quiescent interval slice-selective (qQISS) magnetic resonance angiographic (MRA) strategy that provides simultaneous hemodynamic and luminal evaluation of the cervical arteries. Prospective. Six healthy volunteers (3 female, 3 male, age = 35.7 ± 10.3 years) and 14 patients with cerebrovascular disease (12 female, 2 male, age = 56.6 ± 14.0 years). 3 T, ungated 3D tilted-slab qQISS, pulse-gated 2D phase contrast (PC), ungated 3D PC, and 3D time-of-flight (TOF)gradient-echo protocols. Four readers scored 29 arterial segments on 3D qQISS volumes for image quality using a 4-point scale (1: non-diagnostic, 2: fair, 3: good, 4: excellent). Time-averaged arterial flow velocities and volume flow rates obtained with qQISS and PC protocols were compared. Arterial lumen area and radius measures obtained with 3D protocols were compared in a subgroup. Gwet's AC2; intraclass correlation coefficient (ICC); Pearson's correlation; Bland-Altman. P values <0.05 were considered statistically significant. 3D qQISS provided good-to-excellent image quality for depicting the cervical arteries (mean scores of 3.72 ± 0.55, 3.55 ± 0.66, 3.42 ± 0.72, and 3.66 ± 0.73 for readers 1, 2, 3, and 4) with significant inter-reader agreement (AC2 = 0.91, ICC = 0.53) in image scoring, significantly agreed with pulse-gated 2D PC for time-averaged total flow velocity (ICC = 0.83) and volume flow rate (ICC = 0.92), and significantly agreed with 3D PC for total flow velocity (ICC = 0.70), volume flow rate (ICC = 0.91), and component flow velocity (ICC = 0.89). Compared with 3D PC, 3D qQISS better agreed with 3D TOF for arterial lumen area (ICC = 0.97 vs. 0.72) and radius (ICC = 0.94 vs. 0.74). Nonenhanced 3D qQISS provides high-quality sub-1 mm3 spatial resolution imaging of the cervical arteries, excellent agreement of arterial structural measures with respect to 3D TOF, and time-averaged hemodynamic data without the need for additional PC imaging. Magnetic resonance angiography (MRA), a method for depicting blood vessels within the body, can be used to evaluate arterial diseases and disorders of the neck. MRA methods routinely used to evaluate the neck arteries do not measure blood flow speed and volume, while other methods for obtaining this information provide less accurate pictures of arterial structure and are not routinely collected. This article reports a new method for MRA that clearly and efficiently portrays the neck arteries without using injected dyes, and provides measurements of arterial blood flow speed and volume. 2 TECHNICAL EFFICACY: Stage 1.

Investigation of heat transfer in the geometry of helical screw rheometer having couple stress fluid

AbstractThis study examines the generalized Couette flow of couple stress fluid within the geometry of a helical screw rheometer (HSR). The geometry of the HSR is simplified by modeling the screw as an exposed rectangular channel and flattening the barrel surface. The screw and barrel are maintained at constant temperatures, and , respectively. The viscosity of the fluid is assumed to vary with temperature, and the Reynolds model is applied to describe this temperature‐viscosity relationship. The resulting mathematical formulation leads to nonlinearly coupled ordinary differential equations, with velocity and temperature as unknown functions. To solve for the velocity profiles and temperature distribution, an analytical technique known as the perturbation method is utilized. The expressions for volume flow rates are also derived. A graphical analysis is performed to examine the effects of various dimensionless parameters, such as the couple stress parameter , flight angle , constant number , Brinkman number , and pressure gradients in and ‐directions. It is observed that , and enhance the flow profiles and temperature distribution, while variations in reduce the velocity profile in the ‐direction but increase the net velocity and temperature distribution. The pressure gradient in ‐direction promotes the velocity component in ‐direction with no effects on the velocity component in ‐direction. Similarly, the pressure gradient in ‐direction increases the velocity component in ‐direction with no effects on the velocity component in ‐direction. These findings offer insights into optimizing flow behavior and heat transfer in HSR systems and provide a deeper understanding of the interactions between velocity, temperature, and material properties.

Numerical investigation of unsteady magnetohydrodynamic flow of a Newtonian fluid with variable viscosity in an inclined channel

This research investigates the unsteady flow dynamics of an electrically conducting Newtonian fluid with variable viscosity in an inclined channel under the influence of a uniform magnetic field. The flow is driven by a constant pressure gradient applied at the entrance of the channel, and the governing equations are derived from the Navier–Stokes equation, incorporating the impact of magnetic fields, gravitational force, and viscosity variations. The no-slip boundary condition at the channel walls and appropriate initial conditions are applied. A numerical solution to the non-dimensionalized flow equations is obtained to analyze key flow characteristics, such as velocity profiles, flow rate, and wall stresses. The impact of various dimensionless parameters, including viscosity variation, magnetic field strength, Froude number, and channel inclination angle, on the flow behavior is explored through graphical and tabular presentations. The results provide insights into how these parameters influence the velocity distribution, volumetric flow rate, and wall stresses in the inclined channel, contributing to a deeper understanding of magnetohydrodynamic flows in practical applications.

Simulation investigation on volumetric mixing of the rotary ERD unit and array in the SWRO desalination system

In SWRO desalination system, both low volumetric mixing and high flow capacity of rotary ERD unit is the bottleneck problem at present. Here, a new motor-driven rotary ERD (MD-RERD) is proposed with a large length-diameter ratio rotor and high flow capacity of 110 m3/h. When the length-diameter ratio increases from 14.5 to 18.5 based on unchanged rotor channel diameter, the volumetric mixing of MD-RERD at rotating speed (140 rpm) decreases from 5.503 % to 1.728 % by CFD simulation, which is much lower than that of commercial rotary ERD. Moreover, the MD-RERD shows high energy recovery efficiency of 98.2 %. To further evaluate the mixing performance, an array model composed of 5 MD-RERD units with the flow capacity of 550 m3/h is constructed. The volumetric mixing of the array is 2.339 % under traditional ZZ-array, which is 35.4 % more than that of the single unit due to poor matching degree of volume flowrate between high-pressure route and low-pressure route. Moreover, when the rotor rotates anticlockwise at 140 rpm, the high-pressure route with U-type shows much higher uniformity of flow distribution than Z-type, which is close to that of low-pressure route with Z-type. Therefore, the Z-type is changed to U-type in high-pressure route to construct the UZ-array. Consequently, the matching degree of volume flowrate between the two routes increases, and the volumetric mixing of the array decreases to 1.968 %, which is only 13.9 % more than that of the single unit. It is beneficial to further improve the comprehensive efficiency of the ERD and thus significantly reduce the energy consumption in SWRO desalination system compared to the commercial ERD with a common volumetric mixing of 6 %.

Study of metrological characteristics of household gas meters when measuring the volume flow rate of gas-hydrogen mixtures

The paper presents the results of studies of the influence of pure gaseous hydrogen and gas-hydrogen mixtures and the performance and metrological characteristics of membrane-type gas meters used in the household sector. For the study, membrane-type meters of leading domestic and European manufacturers were pre-selected. A series of static and dynamic tests were conducted for the meters. The static tests involved checking the air-tightness of the meters under the influence of gaseous mixtures. The dynamic tests involved measurements on a simulated test site with a work medium of pure hydrogen as well as hydrogen-methane mixtures. The proportions of the mixtures used were: 80% of methane and 20% of hydrogen, and 90% of methane and 10% of hydrogen respectively. A structural diagram of the measuring system was developed. The measurements were performed by comparing the volume of the gas that passed through the experimental meter with the volume measured by the reference meter. The measuring system was equipped with a means for measuring the pressure and temperature of the measuring medium to bring the results of the experiments to standard conditions. As a reference means in the assembled measuring system, a drum-type gas meter with a calibration characteristic pre-determined under laboratory conditions with a work air medium was used. After the experimental studies with the work hydrogen medium and hydrogen gas mixtures under the conditions of the test site, the metrological characteristics were re-determined under laboratory conditions for the reference meter. To conduct the experiments with the maximum possible accuracy and to exclude the influence of additional errors on the measurement result, a specialized software was developed to automate the measurements of the volume of the gas passing through the reference meter, measuring the pressure and temperature of the work medium and fixing the required value of the gas volume flow rate. The results of the experiments for several meters are presented in the form of tabular values and graphs. General conclusions were made regarding the influence of hydrogen and gas-hydrogen mixtures on the change in metrological characteristics of household gas meters.

Highly Air-Stable N-Doped Two-Dimensional Violet Phosphorus with Atomically Flat Surfaces.

Few-layer violet phosphorus (VP) shows excellent potential in optoelectronic applications due to its unique in-plane anisotropy and high mobility. However, the poor air stability of VP severely limits its practical applications. This article reports highly air-stable VP obtained by a two-step nitrogen plasma treatment where the nitrogen volume flow rate is controlled to coordinate physical etching and chemical doping. Specially, this plasma process can remove partial oxidations formed on the VP surface with barely etching to the intrinsic VP surface but efficiently incorporates nitrogen into VP, resulting in surface nitrogen-doped VP (N-VP) nanosheets with atomically smooth surfaces that exhibit excellent air stability. Atomic force microscopy images show that the N-VP nanosheet, nearing a monolayer thickness, maintained its surface morphology and flatness unchanged in ambient air for over 60 days. The improved stability of N-VP can be partly due to its atomically smooth surface, which reduces the number of active or oxidation sites. Further elucidation was made by density functional theory calculations, showing that this ultrastability may intrinsically be attributed to repairing P vacancies by N dopants. This research provides a feasible strategy for significantly enhancing the durability of VP.

Evaluation of Coal Repowering Option with Small Modular Reactor in South Korea

The Paris Agreement emphasizes the need to reduce greenhouse gas emissions, particularly from coal power. One suggested approach is repowering coal-fired power plants (CPPs) with small modular reactors (SMRs). South Korea plans to retire CPPs in the coming decades and requires alternative options for coal-fired energy. This study presents a scoping analysis comparing variable renewable energy (VRE) sources with SMRs for repowering CPPs in the Korean context. The analysis indicates that SMRs may be a more favorable option than VRE sources, particularly due to their load-following capabilities. In this study, two types of SMRs were investigated: high-temperature gas reactors (HTGRs) and pressurized water reactors (PWRs). HTGRs are suitable to fit the high-temperature operating conditions of steam turbines but require multiple units due to their low volumetric flow rates. PWRs, while matching the volumetric flow rate of existing CPP turbines, require additional thermal energy sources to meet the high-temperature operating conditions of steam turbines. Lastly, an analysis of necessary regulatory and legislative changes in South Korea’s nuclear framework is presented, identifying several key regulatory issues for repowering coal with nuclear energy.

Analytical Study of Blood Flow through a Tapered Stenosed Artery: Impact of Arterial Shape on Fluid Dynamics

This study presents an analytical investigation into the dynamics of blood flow through a tapered stenosed artery, focusing on the influence of arterial shape on fluid dynamics. The arterial medium is modeled as a power law fluid. Governing equations for laminar, incompressible, and non-Newtonian fluid flow subject to appropriate boundary conditions are solved. Perturbation mathematical method has used to get the analytical expressions. Equations are derived for key flow parameters, including velocity components, volumetric flow rate, wall shear stress, and pressure gradient. The findings reveal significant insights into the impact of arterial shape on fluid dynamics, highlighting how variations in artery geometry affect velocity profiles, pressure gradients, and wall shear stress distributions. Specifically, the study observes notable changes in wall shear stress with alterations in the tapering angle of artery. This research contributes to a deeper understanding of the complex interplay between arterial geometry and blood flow dynamics, with implications for diagnosis and treatment of vascular diseases.

Lumped parameter simulations of cervical lymphatic vessels: dynamics of murine cerebrospinal fluid efflux from the skull

BackgroundGrowing evidence suggests that for rodents, a substantial fraction of cerebrospinal fluid (CSF) drains by crossing the cribriform plate into the nasopharyngeal lymphatics, eventually reaching the cervical lymphatic vessels (CLVs). Disruption of this drainage pathway is associated with various neurological disorders.MethodsWe employ a lumped parameter method to numerically model CSF drainage across the cribriform plate to CLVs. Our model uses intracranial pressure as an inlet pressure and central venous blood pressure as an outlet pressure. The model incorporates initial lymphatic vessels (modeling those in the nasal region) that absorb the CSF and collecting lymphatic vessels (modeling CLVs) to transport the CSF against an adverse pressure gradient. To determine unknown parameters such as wall stiffness and valve properties, we utilize a Monte Carlo approach and validate our simulation against recent in vivo experimental measurements.ResultsOur parameter analysis reveals the physical characteristics of CLVs. Our results suggest that the stiffness of the vessel wall and the closing state of the valve are crucial for maintaining the vessel size and volume flow rate observed in vivo. We find that a decreased contraction amplitude and frequency leads to a reduction in volume flow rate, and we test the effects of varying the different pressures acting on the CLVs. Finally, we provide evidence that branching of initial lymphatic vessels may deviate from Murray’s law to reduce sensitivity to elevated intracranial pressure.ConclusionsThis is the first numerical study of CSF drainage through CLVs. Our comprehensive parameter analysis offers guidance for future numerical modeling of CLVs. This study also provides a foundation for understanding physiology of CSF drainage, helping guide future experimental studies aimed at identifying causal mechanisms of reduction in CLV transport and potential therapeutic approaches to enhance flow.

Correlation between P2-PCA volume flow rate and BOLD cerebrovascular reactivity in patients with symptomatic carotid artery occlusion.

Identifying and assessing hemodynamic and flow status in patients with symptomatic internal carotid artery (ICA) occlusion is crucial for evaluating recurrent stroke risk. The aim of this study was to analyze the correlation between two quantitative imaging modalities: (1) blood oxygenation level-dependent (BOLD) cerebrovascular reactivity (CVR) and (2) quantitative magnetic resonance angiography (qMRA) with non-invasive optimal vessel analysis (NOVA), measuring volume flow rate (VFR). Comparing these modalities is relevant for assessing collateral circulation and hemodynamic impairment. In this retrospective analysis of prospectively collected data, 37 symptomatic patients with unilateral ICA occlusion, who underwent both, NOVA-qMRA and BOLD-CVR investigation, were included. The correlation analysis between NOVAqMRA-derived second segment of the posterior cerebral artery (PCA-P2) VFR and BOLD-CVR (hemispheric and MCA territory CVR) was done by using a linear mixed-effects model. A moderate correlation was found between P2-VFR and BOLD-CVR values for the ipsilateral MCA territory (|r|=0.44, R2=0.2, p<0.001) and the ipsilateral hemisphere (|r| =0.39, R2=0.15, p<0.001), indicating that 20% of the variance in P2-VFR can be explained by the BOLD-CVR of the MCA territory and 15% by the BOLD-CVR of the affected hemisphere. This correlation suggests that impaired BOLD-CVR is partly linked to an increased PCA-P2 volume flow rate, potentially indicating the activation of leptomeningeal collaterals in severe hemodynamic conditions. Both imaging techniques could aid clinicians in in creating personalized treatment strategies for patients with symptomatic ICA occlusion. ACA = anterior cerebral artery; BOLD = blood oxygenation-level dependent; CVR = cerebrovascular reactivity; M1 = first segment of the middle cerebral artery; MCA =middle cerebral artery; NOVA = non-invasive optimal vessel analysis; P2 = second segment of the posterior cerebral artery; PCA = posterior cerebral artery; PCOM= posterior communicating artery; VFR = volume flow rate.

Volumetric supraglottal jet flow field analysis in synthetic multilayered self-oscillating vocal fold model

Volumetric supraglottal jet flow field analysis in synthetic multilayered self-oscillating vocal fold model

Investigating hull dryer unit performance: Experiments and modeling of drying time

Hull compaction is an important waste management practice for volume reduction of hollow metallic hull waste generated in the back end of the nuclear fuel cycle. The hull waste should be totally dried of wash solution before high pressure compaction to avoid radiolysis and corrosion phenomena.[ 1 ] In the present work, the influence of various operating parameters (volumetric air flow rate, inlet air temperature, and quantity of hull waste) on the performance of a hull dryer unit has been investigated experimentally. It was observed that drying time exhibited an inverse relationship with both air flow rate and temperature. Furthermore, an increase in the mass of hull waste within the batching can led to improved dry air utilization efficiency. To enable a more comprehensive understanding of the drying process and accurate prediction of drying times, a mathematical model was formulated. A new methodology for estimating the specific surface area of randomly packed hull pieces has been presented. A comprehensive comparison of simulated data with measured exhaust air properties (mass absolute humidity, exit air temperature) and drying times was performed. The close agreement between model predictions and experimental results, with mean absolute percentage error ranging from 2.39923 to 25.21 established strong validation of the model, confirming its predictive capability. This validated model provides a robust foundation for designing future hull dryer units by enabling the calculation of optimal process parameters for various drying time requirements. The study shows that the direct contact hot air heating is a promising technique for drying of hull waste and can be accepted in fast reactor fuel cycle.

Peristaltic pumping of viscoelastic fluid in a diverging channel: effects of magnetic field and surface roughness

Purpose Surface properties (smooth or roughness) play a critical role in controlling the wettability, surface area and other physical and chemical properties like fluid flow behaviour over the rough and smooth surfaces. It is reported that rough surfaces are offering more significant insights as compared to smooth surfaces. The purpose of this study is to examine the effects of surface roughness in the diverging channel on physiological fluid flows. Design/methodology/approach A mathematical formulation based on the conservation of mass and momentum equations is developed to derive exact solutions for the physical quantities under the assumption of low Reynolds numbers and long wavelengths, which are appropriate for biological transport scenarios. Findings The results reveal that an increase in surface roughness reduces axial velocity and volumetric flow rate while increasing pressure distribution and turbulence in skin friction. Research limitations/implications These findings offer valuable insights for biological flow analysis, highlighting the effects of surface roughness, non-uniformity of the channel and magnetic fields. Practical implications These findings are very much applicable for designing the pumping devices for transportation of the fluids in non-uniform channels. Originality/value This study examines the impact of surface roughness on the peristaltic pumping of viscoelastic (Jeffrey) fluids in diverging channels with transverse magnetic fields.