Characterization Of Flow Patterns Research Articles

Characterization of internal jugular vein region-specific distension and flow patterns during progressive volume shifting.

Blood volume shifts during postural adjustment leads to irregular distension of the internal jugular vein (IJV). In microgravity, distension may contribute to flow stasis and thromboembolism, though the regional implications and associated risk remain unexplored. We characterized regional differences in IJV volume distension and flow complexity during progressive head-down tilt (HDT) (0°, -6°, -15°, -30°) using conventional ultrasound and vector flow imaging. We also evaluated low-pressure thigh cuffs (40 mmHg) as a fluid shifting countermeasure during -6° HDT. Total IJV volume expanded 139±95% from supine (4.6±2.7 mL) to -30° HDT (10.3±5.0 mL). Blood flow profiles had greater vector uniformity at the cranial IJV region (P<0.01) and became more dispersed with increasing tilt (P<0.01). Qualitatively, flow was more uniform throughout the IJV during its early flow cycle phase, and more disorganized during late flow phase. This disorganized flow was accentuated closer to the vessel wall, near the caudal region, and during greater HDT. Low-pressure thigh cuffs during -6° HDT decreased IJV volume at the cranial region (-12±15%; P<0.01) but not the caudal region (P=0.20), although flow uniformity was unchanged (both regions,P>0.25). We describe a distensible IJV accommodating large volume shifts along its length. Prominent flow dispersion was primarily found at the caudal region, suggesting multi-directional blood flow. Thigh cuffs appear effective for decreasing IJV volume but effects on flow complexity are minor. Flow complexity along the vessel length is likely related to IJV distension during chronic volume shifting and may be a precipitating factor for flow stasis and future thromboembolism risk.

Characterization of liquid-liquid two-phase flow patterns and mass transfer coefficients in Human-shaped microchannels

Based on the principle of splitting and recombining, this study designed and fabricated millimeter-scale Human-shaped microchannels. The research focused on investigating the flow patterns and mass transfer characteristics of liquid-liquid two-phase flow within the Human-shaped microchannels. The experiment utilized a water and n-butanol system to investigate the flow behavior of liquid-liquid two-phase in the channel with a flow rate ratio of 1. When the total volumetric flow rate increases from 120 µl/min to 2400 µl/min, the flow pattern experiences slug flow, slug-droplet flow, parallel flow and non-steady flow patterns respectively. The study investigated the impact of factors including total flow rate, feed method, angle, curvature, channel width, phase ration extraction efficiency and mass transfer coefficients. The Human-shaped channel exhibited superior mass transfer performance compared to conventional microchannels due to its advantageous configuration. The higher the included angle is, the stabler the flow pattern within the channel, resulting in a better mass transfer performance. Furthermore, the absence of curvature is more favorable for achieving higher mass transfer efficiency. In the experiments, the overall volume mass transfer coefficient ranged from 0.007 to 0.1742 s−1. This study can provide insights for the development and structural optimization of microchannels based on the split-recombine principle.

Low Observable Uncrewed Aerial Vehicle Wind Tunnel Model Design, Manufacturing, and Aerodynamic Characterization

Developing wind tunnel models is time consuming, labor intensive, and expensive. Rapid prototyping for wind tunnel tests is an effective, faster, and cheaper method to obtain aerodynamic performance results while considerably reducing acquisition time and cost for the models. Generally, the rapid prototyping models suffer from insufficient stiffness or strength to withstand the loads generated during a wind tunnel test. In the present study, a rapid prototype model reinforced with metallic inserts was produced to experimentally investigate the aerodynamic characteristics of an uncrewed aerial vehicle with various wingtip deflections. The fused deposition modeling process was used to make the outer mold, whereas the metallic parts were produced using laser cutting and the computer numerical control machining process. Then, the model was evaluated both experimentally and numerically. The test campaign presented in this work was conducted in the de Havilland low-speed wind tunnel facility at the University of Glasgow. For better characterization of flow patterns dominated by leading edge vortices, numerical simulations were run using OpenFOAM 8.0 and validated with experimental data. The experimental data obtained from the hybrid rapid-prototyped model agreed well with the numerical results. This demonstrates the efficacy of hybrid rapid-prototyped models in providing reliable results for initial baseline aerodynamic database development within a short period and at a reduced cost for wind tunnel tests.

Novel insights into diminished cardiac reserve in non-obstructive hypertrophic cardiomyopathy from four-dimensional flow cardiac magnetic resonance component analysis.

Hypertrophic cardiomyopathy (HCM) is characterized by hypercontractility and diastolic dysfunction, which alter blood flow haemodynamics and are linked with increased risk of adverse clinical events. Four-dimensional flow cardiac magnetic resonance (4D-flow CMR) enables comprehensive characterization of ventricular blood flow patterns. We characterized flow component changes in non-obstructive HCM and assessed their relationship with phenotypic severity and sudden cardiac death (SCD) risk. Fifty-one participants (37 non-obstructive HCM and 14 matched controls) underwent 4D-flow CMR. Left-ventricular (LV) end-diastolic volume was separated into four components: direct flow (blood transiting the ventricle within one cycle), retained inflow (blood entering the ventricle and retained for one cycle), delayed ejection flow (retained ventricular blood ejected during systole), and residual volume (ventricular blood retained for >two cycles). Flow component distribution and component end-diastolic kinetic energy/mL were estimated. HCM patients demonstrated greater direct flow proportions compared with controls (47.9 ± 9% vs. 39.4 ± 6%, P = 0.002), with reduction in other components. Direct flow proportions correlated with LV mass index (r = 0.40, P = 0.004), end-diastolic volume index (r = -0.40, P = 0.017), and SCD risk (r = 0.34, P = 0.039). In contrast to controls, in HCM, stroke volume decreased with increasing direct flow proportions, indicating diminished volumetric reserve. There was no difference in component end-diastolic kinetic energy/mL. Non-obstructive HCM possesses a distinctive flow component distribution pattern characterised by greater direct flow proportions, and direct flow-stroke volume uncoupling indicative of diminished cardiac reserve. The correlation of direct flow proportion with phenotypic severity and SCD risk highlight its potential as a novel and sensitive haemodynamic measure of cardiovascular risk in HCM.

Characterization of Aortic Flow Patterns by High‐Frame‐Rate Blood Speckle Tracking Echocardiography in Children

Background Blood speckle tracking echocardiography allows for direct quantification of interventricular and aortic flow profiles, principally in children. Here, we sought to demonstrate the feasibility and reproducibility of blood speckle tracking echocardiography in the aortas of healthy children. Methods and Results One hundred healthy White children evaluated for the screening of congenital heart disease were prospectively enrolled. Echocardiographic examinations were performed using a Vivid E 95 ultrasound system, with blood speckle tracking from a focused and zoomed view of the aortic root and the ascending aorta. Vortex position, height (mm), width (mm), sphericity index, and area (cm2) were measured and indexed by body surface area. Median (interquartile range) age was 8.2 (5.6-11.0) years, median (interquartile range) weight was 28 (19-35) kg, and median (interquartile range) body surface area was 1.01 (0.79-1.16) m2. Vortices were visualized in only a single phase of the cardiac cycle in 25 subjects-14 (56.0%) were evident in early diastole and 11 (44.0%) in late systole. Vortices visualized in diastole had a mean area of 0.27±0.1 cm2/m2, while those in systole had a mean area of 0.34±0.12 cm2/m2. In a subset of 20 patients, inter- and intraobserver coefficient of variation and intraclass correlation coefficients were determined and showed good reproducibility. Conclusions We demonstrate feasibility and reproducibility of blood speckle tracking and identified vortical flow patterns in the aortic root and ascending aorta in healthy children. These data may serve as a baseline for evaluating aortic flow patterns in children with congenital and acquired heart disease.

Radiomics-based aortic flow profile characterization with 4D phase-contrast MRI.

4D PC MRI of the aorta has become a routinely available examination, and a multitude of single parameters have been suggested for the quantitative assessment of relevant flow features for clinical studies and diagnosis. However, clinically applicable assessment of complex flow patterns is still challenging. We present a concept for applying radiomics for the quantitative characterization of flow patterns in the aorta. To this end, we derive cross-sectional scalar parameter maps related to parameters suggested in literature such as throughflow, flow direction, vorticity, and normalized helicity. Derived radiomics features are selected with regard to their inter-scanner and inter-observer reproducibility, as well as their performance in the differentiation of sex-, age- and disease-related flow properties. The reproducible features were tested on user-selected examples with respect to their suitability for characterizing flow profile types. In future work, such signatures could be applied for quantitative flow assessment in clinical studies or disease phenotyping.

MP37-13 INTER-RATER AND INTRA-RATER RELIABILITY OF UROFLOWMETRY INTERPRETATION IN ADULT WOMEN

You have accessJournal of UrologyCME1 Apr 2023MP37-13 INTER-RATER AND INTRA-RATER RELIABILITY OF UROFLOWMETRY INTERPRETATION IN ADULT WOMEN Leslie M. Rickey, Elizabeth R. Mueller, Diane K. Newman, Alayne D. Markland, Chloe Falke, Kyle Rudser, and Emily S. Lukacz Leslie M. RickeyLeslie M. Rickey More articles by this author , Elizabeth R. MuellerElizabeth R. Mueller More articles by this author , Diane K. NewmanDiane K. Newman More articles by this author , Alayne D. MarklandAlayne D. Markland More articles by this author , Chloe FalkeChloe Falke More articles by this author , Kyle RudserKyle Rudser More articles by this author , and Emily S. LukaczEmily S. Lukacz More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003275.13AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Non-invasive uroflowmetry is often used to assess lower urinary tract symptoms (LUTS). However, interpretation and characterization of flow patterns is not well established. Subjective interpretation is the most common approach for flow curve classification, and variable parameters have been reported for uroflowmetry curves. We sought to describe the reliability of uroflowmetry curve interpretation in adult women. METHODS: Uroflowmetry studies were obtained in 296 adult women who participated in an observational Prevention of Lower Urinary Tract Symptoms (PLUS) Research Consortium cohort study. Four investigators with expertise in female LUTS and urodynamics reviewed and categorized each tracing for inter-rater reliability and a random subset of 50 tracings were re-reviewed by each investigator for intra-rater reliability. The uroflowmetry tracings were rated using categories of continuous, continuous with fluctuation, interrupted, and prolonged. Tracings could also be categorized as uninterpretable or ambivalent if the voided volume was <150ml or the reviewer could not assign one of the pattern categories. Other parameters included flow rate, voided volume, time to maximum flow, and voiding time. Agreement between raters was summarized with kappa (k) statistics and percentage where at least 3 raters agreed. RESULTS: The mean age of participants was 44.8±18.3years. Participant age categories were: 18-24y 20%; 25-34y 18%; 35-64y 43%; ≥65y 19%. Nine percent described their race as Asian, 31% Black, 62% White and 95% non-Hispanic origin. The inter-rater reliability was highest for the continuous flow category (k=0.65), 0.41 for continuous with fluctuation, 0.47 for interrupted, and 0.41 for prolonged flow curves. Agreement amongst at least 3 raters occurred in 74.3% uroflow curves (45.9% for continuous, 13.5% for continuous with fluctuation, 3.4% for interrupted, and 4.1% for prolonged). For intra-rater reliability, the mean kappa across the four raters was 0.72 with a range of 0.57-0.85. CONCLUSIONS: Currently accepted uroflowmetry curve categories have fair to moderate inter-rater reliability and is lower for flow curves that don’t meet “continuous” criteria. Given the subjective nature of interpreting uroflowmetry data, more consistent and clear parameters may enhance reliability for use as a research parameter. Algorithms that can process numerical and pattern data may also improve the reliability of uroflowmetry studies as a diagnostic and predictive tool for LUTS interventions. Source of Funding: The content of this [abstract/ presentation/ poster] is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.The Prevention of Lower Urinary Tract Symptoms (PLUS) Research Consortium is supported by the National Institutes of Health (NIH) through cooperative agreements (grants U24DK106786, U01DK106853, U01DK106858, U01DK106898, U01DK106893, U01DK106827, U01DK106908, U01DK106892, U01DK126045). © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e519 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Leslie M. Rickey More articles by this author Elizabeth R. Mueller More articles by this author Diane K. Newman More articles by this author Alayne D. Markland More articles by this author Chloe Falke More articles by this author Kyle Rudser More articles by this author Emily S. Lukacz More articles by this author Expand All Advertisement PDF downloadLoading ...

The Characterization of Hydrodynamic Flow Patterns in the Kawal River Estuary, Bintan Island, Indonesia

One of the pivotal oceanographic factors impacting the hydrodynamic attributes of the waters within the Kawal River Estuary is the prevailing current. This current pattern in the Kawal River estuary exhibits a dynamic nature, primarily under the influence of wind and tidal dynamics. The Kawal River Estuary, as a confluence zone of riverine and oceanic currents, manifests as a dynamically evolving aquatic environment. The investigation was conducted at the Kawal River Estuary in Bintan Regency during the months of September 2021 and January 2022. The research employed the MIKE 21 software, examining two distinct tidal states: high tide and low tide. In September, the sound velocity values averaged 1538.647 m/s at the water surface, 1539.984 m/s within the water column, and 1541.436 m/s at the seabed. In contrast, January recorded sound velocity values of 1534.517 m/s at the surface, 1535.613 m/s within the water column, and 1536.312 m/s at the seabed. Current velocities in September ranged between 0.02 m/s and 0.037 m/s, with a predominant southward direction, while in January, they varied from 0.02 m/s to 0.59 m/s, also exhibiting a southward trajectory. Notably, the swifter current velocities observed in January are attributed to the influence of the northern season.

Doppler echocardiography in a healthy, non-sedated Southern Sea Lion (Otaria flavescens) - a preliminary approach about the feasibility and clinical utility.

Echocardiography is commonly used in veterinary clinical practice for many species but is not as easily applied in non-sedated marine mammals. Additionally, Doppler echocardiography provides further information on hemodynamics, estimation of cardiac output, characterization of flow patterns, and diastolic function. However, its applications in marine mammals have not been as widely explored either. The present report aimed to characterize the left ventricle structure and function of the Southern Sea Lion (Otaria flavescens) through a Doppler echocardiography study. Data were obtained from a healthy animal trained for different veterinary examination routines. This communication constitutes the first report of Doppler echocardiography with stroke volume, and cardiac output measurement in pinnipeds, and the first report of measurement of myocardial performance index in aquatic mammals. This data brought initial information about in vivo structure and function of the heart of the Southern Sea Lion that can be safely and effectively evaluated with the use of transthoracic Doppler echocardiography. Our data have both clinical and research implications for future studies evaluating diseases of the cardiopulmonary system in pinnipeds, and cardiovascular physiology investigation in diving mammals.

Two-phase flow characterization through recurrence quantification analysis of the dominant features of experimental dynamics

This paper describes a novel approach to the analysis of the experimental void fraction time series detected in air–water upward two-phase flows within a vertical channel. Singular Value Decomposition (SVD) is applied to the experimental void fraction time series in order to assess a novel state space spanned by the principal components of the flow dynamics; in fact, this was demonstrated in a previous study to be effective in separating the dominant features from noise-like dynamics and, above all, in evidencing the existence of recurrent behaviours.As recurrence is a typical and fundamental signature of low-order deterministic nonlinear dynamics, the present study aims at reaching a detailed insight on the recurrent structures that characterize the experimental void fraction time series, which were measured during an experimental campaign encompassing the entire spectrum of patterns in vertical air–water upward flows.The main novelty of the present study is the adoption of the tools collectively known as Recurrence Quantification Analysis not directly to the experimental time series, as it is increasingly proposed in the analysis of two-phase flows, but to their most important principal components. The goal is to obtain a more reliable characterization of two-phase flow patterns, which is based only on the relevant features and, hence, is unbiased by noisy high-order dynamics.Reported results show that the present approach indeed provides a powerful tool for the characterisation of the variety of complex dynamics exhibited by two-phase flows, as well as for flow pattern classification.

Modeling and Characterization of Traffic Flow Patterns and Identification of Airspace Density for UTM Application

Current airspace has limited resources, and the widespread use of unmanned aerial vehicles (UAVs) increases airspace density, which is already crowded with manned aircraft. This demands the improvement of airspace safety and capacity while considering all parametric uncertainties that may hinder aircraft and UAV mobility such as dynamic airspace structures and weather conditions. This paper proposes a data analytics framework to characterize traffic flow patterns of unmanned traffic management (UTM) airspace by analyzing simulated historical data. Mission patterns are characterized and identified by considering multiple UAV missions and scenarios with different priority levels to highlight UAVs’ trajectories and deviations from the actual path due to these constraints. The pertinent data analysis supports risk analysis and improves trajectory planning in different airspace regions considering all dynamic parameters such as extreme weather, emergency services, and dynamic airspace structures. The data processing framework, which is density-based spatial clustering of applications with noise (DBSCAN), identified significant deviations in mission patterns with almost 82% confidence level. The UTM traffic flow characterization is conducted by three key characterization parameters mainly Distance from Centroid (DFC), Distance to Complete Mission (DTCM) and Time to Complete Mission (TTCM). This work also analyzed the airspace congestion using the Kernel density estimation (KDE). This analysis identified some regions of interference as potential congested areas representing safety concerns. The proposed framework is envisioned to assist UTM authority by characterizing air traffic behavior, managing its flow, improving airspace design, and providing the basis for developing predictive capabilities that support traffic flow management.

Point-Process Modeling and Divergence Measures Applied to the Characterization of Passenger Flow Patterns of a Metro System

The problem of characterizing the passengers’ movement in a public transport system has been considered in the literature for analysis, simulation and optimization purposes. In particular, origin-destination matrices are commonly used to describe the total number of passengers that travel between two points during a given time interval. In this paper, we propose to model the instantaneous rate of arrival of passengers for the origin-destination pairs of a metro system using point processes. More specifically, we apply the Expectation-Maximization algorithm to estimate the parameters of a Gaussian mixture intensity function for the daily flow of passengers using data from multiple days provided by EFE Valparaíso. The uncertainty in the parameter estimates is quantified computing standard errors and confidence intervals. Secondly, we quantitatively analyze the similarity of the obtained intensity functions among the different origin-destination pairs. In particular, we propose a dissimilarity index based on the Kullback-Leibler divergence and we apply this index in hierarchical agglomerative and partitioning methods to cluster origin-destination pairs with similar daily flow of passengers. The obtained numerical results confirm expert knowledge about the passengers’ behavior in EFE Valparaíso metro system and, more interestingly, provide additional insights on the passengers’ behaviour for specific origin-destination pairs.

Three-Phase Flow Tomography System in Upward-Vertical High-Viscous-Oil/Water/Gas Flow

A new three-phase flow tomography system is presented in this work. The system was developed to be applied in high-viscous-oil/water/gas flow arranged in different flow patterns, with the three fluids present simultaneously in a crossing point. The primary measurement is based on a simpler and reliable digital in-phase/quadrature (IQ) demodulator and a wire-mesh sensor (WMS), but the system is capable of including different types of primary measurements. Dynamic three-phase flow tests were carried out to verify the system performance and compare its results with the ones obtained by quick-closing valves (QCVs) and a high-speed video camera. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In situ</i> volumetric fractions and flow patterns were compared. The experiments were conducted in a vertical glass pipe of 50-mm i.d. and 12-m height. The observed three-phase flow patterns were water-continuous churn flow with dispersed bubbles and oil drops (WChBoDo), water-continuous slug flow with Taylor bubbles, spherical bubbles, and oil drops (WPiBoDo), and oil-continuous slug flow with Taylor bubbles, spherical bubbles, and water drops (OPiBoDi). Compared with the measurements using QCVs, the average relative errors of the measured volumetric phase fractions were 12% for water, 13% for air, and 22% for oil. The experimental results, including the details of the flow inside the pipe, the phase distributions, and the objective characterization of flow patterns, suggest that the proposed system is a promising option for three-phase flow-related studies and developments. The proposed technique can reach 8930 frames/s with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\times16$ </tex-math></inline-formula> WMS.

Beyond Vessel Diameters: Non-invasive Monitoring of Flow Patterns and Immune Cell Recruitment in Murine Abdominal Aortic Disorders by Multiparametric MRI.

The pathophysiology of the initiation and progression of abdominal aortic aneurysms (AAAs) and aortic dissections (AADs) is still unclear. However, there is strong evidence that monocytes and macrophages are of crucial importance in these processes. Here, we utilized a molecular imaging approach based on background-free 19F MRI and employed perfluorocarbon nanoemulsions (PFCs) for in situ 19F labeling of monocytes/macrophages to monitor vascular inflammation and AAA/AAD formation in angiotensin II (angII)-treated apolipoproteinE-deficient (apoE−/−) mice. In parallel, we used conventional 1H MRI for the characterization of aortic flow patterns and morphology. AngII (1 μg/kg/min) was infused into apoE−/− mice via osmotic minipumps for 10 days and mice were monitored by multiparametric 1H/19F MRI. PFCs were intravenously injected directly after pump implantation followed by additional applications on day 2 and 4 to allow an efficient 19F loading of circulating monocytes. The combination of angiographic, hemodynamic, and anatomical measurements allowed an unequivocal classification of mice in groups with developing AAAs, AADs or without any obvious aortic vessel alterations despite the exposure to angII. Maximal luminal and external diameters of the aorta were enlarged in AAAs, whereas AADs showed either a slight decrease of the luminal diameter or no alteration. 1H/19F MRI after intravenous PFC application demonstrated significantly higher 19F signals in aortae of mice that developed AAAs or AADs as compared to mice in which no aortic disorders were detected. High resolution 1H/19F MRI of excised aortae revealed a patchy pattern of the 19F signals predominantly in the adventitia of the aorta. Histological analysis confirmed the presence of macrophages in this area and flow cytometry revealed higher numbers of immune cells in aortae of mice that have developed AAA/AAD. Importantly, there was a linear correlation of the 19F signal with the total number of infiltrated macrophages. In conclusion, our approach enables a precise differentiation between AAA and AAD as well as visualization and quantitative assessment of inflammatory active vascular lesions, and therefore may help to unravel the complex interplay between macrophage accumulation, vascular inflammation, and the development and progression of AAAs and AADs.

Universal scaling of human flow remain unchanged during the COVID-19 pandemic

To prevent the spread of the COVID-19 pandemic, governments in various countries have severely restricted the movement of people. The large amount of detailed human location data obtained from mobile phone users is useful for understanding the change of flow patterns of people under the effect of pandemic. In this paper, we observe the synchronized human flow during the COVID-19 pandemic using Global Positioning System data of about 1 million people obtained from mobile phone users. We apply the drainage basin analysis method which we introduced earlier for characterization of macroscopic human flow patterns to observe the effect of the spreading pandemic. Before the pandemic the afternoon basin size distribution has been approximated by an exponential distribution, however, the distribution of Tokyo and Sapporo, which were most affected by the first wave of COVID-19, deviated significantly from the exponential distribution. On the other hand, during the morning rush hour, the scaling law holds universally, i.e., in all cities, even though the number of moving people in the basin has decreased significantly. The fact that these scaling laws, which are closely related to the three-dimensionality structure of the city and the fractal structure of the transportation network, have not changed indicates that the macroscopic human flow features are determined mainly by the means of transport and the basic structure of cities which are invariant of the pandemic.

Simulations of stably stratified flow past two spheres at Re = 300

Flows past two spheres immersed in a horizontally moving, linearly stratified fluid are investigated at a moderate Reynolds number of 300. Characterization of flow patterns considers representative geometrical configurations defined by varying both the distance between the spheres and their relative orientation to the free stream direction. Simulations are performed on unstructured meshes chosen to accurately resolve the dynamics of fluids in regions close to the spheres for Froude numbers Fr∈[0.25,∞]. Results illustrate the evolution of boundary layers, separation, and the wakes interaction under the influence of a gravity induced buoyancy force. Computations utilize a limited area, nonhydrostatic model employing non-oscillatory forward-in-time integration based on the multidimensional positive definite advection transport algorithm. The model solves the Navier–Stokes equations in the incompressible Boussinnesq limit, suitable for describing a range of mesoscale atmospheric flows. Results demonstrate that stratification progressively dominates the flow patterns as the Froude number decreases and that the interactions between the two spheres' wakes bear a resemblance to atmospheric flows past hills.

High-resolution high-speed void fraction measurements in helically coiled tubes using X-ray radiography

Helical coil heat exchangers are known for their superior heat transfer, compactness and robustness against thermal expansion compared to systems with straight pipes. Due to all these benefits, they became quite popular in the last few decades in various industries such as pharmaceutical, chemical or nuclear. Generally, they are used in a single-phase environment or with evaporation taking place on the shell side. However, in most of the steam generator designs adopted in advanced nuclear reactors, the two-phase mixture flows upward within the vertically oriented helical coils. In addition, physical two-phase phenomena taking place inside helical tubes differ significantly from those in straight pipes due to inherent centrifugal and torsion effects. To improve the computational models used to predict the thermal hydraulic performance of such steam generators, experimental characterization and identification of different two-phase flow patterns in helical coils are essential. In the present paper, high-resolution measurements of the void fraction distribution for an adiabatic upward air–water two-phase flow were conducted in a transparent helically coiled acrylic pipe by means of high-speed X-ray radiography at ambient conditions. Various void fraction based features such as probability density function estimates, profiles over the height of the pipe cross-section and temporal evolutions were used to identify and characterize flow regimes. A total of 13 measurements are presented in this paper, classified into six flow regimes, namely: bubbly, plug, wavy, slug, slug-annular and annular flow. The obtained flow regimes are in accordance with flow regime characterizations and transition criteria already reported in literature.

Vector flow imaging using a deep neural network

Vector flow imaging (VFI) estimates blood flow velocities in both azimuth and axial dimensions. VFI has promising applications in the characterization of complex flow patterns, including cardiac flow and abdominal flow imaging. Conventional VFI relies on the use of multiple angles in transmit or receive, or speckle tracking. They are computationally intensive and estimate quality may be sacrificed to improve computational speed. In this work, we report a vector flow estimation technique using a deep neural network. The network extracts feature from high-pass filtered beamsummed RF data of two consecutive Doppler packets. For each packet, the RF data have azimuth and axial dimensions. It then performs estimation of vector flow in the feature space, and maps the estimate back to the spatial domain. The total computation time is 0.11 s for a pair of Doppler frames of 1024 × 128 samples. The performance of the method is characterized using Field II simulation studies, flow phantom studies, and an in vivo liver study with a Verasonics Vantage 256 scanner. The simulation and flow phantom studies show good agreement between the estimates and the ground truth. The in vivo studies demonstrate that the method is capable of characterizing complex flow patterns in human liver vessels.

Identification, Characterization, and Prediction of Traffic Flow Patterns in Multi-Airport Systems

Efficient planning of airport capacity is key for the successful accomplishment of traffic flow management. Yet, the dynamic and uncertain behavior of capacity-determining factors makes it difficult to estimate flow rates precisely, especially for strategic planning horizons. Metroplex systems impose additional challenges in this decision-making process because of relevant operational interdependencies between the closely located airports. This paper presents a data-driven framework to identify, characterize, and predict traffic flow patterns in the terminal area of multi-airport systems toward improved capacity planning decision support in complex airspace. Through the identification and characterization of patterns in the terminal area traffic flows, we learn recurrent utilization patterns of runways and airspace as well as relevant decision factors, and use that knowledge to develop descriptive models for metroplex configuration prediction and capacity estimation. The framework is based on the application of machine learning methods on historical flight tracks, weather forecasts, and airport operational data. A multi-layer clustering analysis is first performed to mine spatial and temporal trends in flight trajectory data for identification of traffic flow patterns. Based on this knowledge, a multi-way classification model is developed to generate probabilistic forecasts of the metroplex traffic flow structure for look-ahead times of up to eight hours. Finally, an empirical approach for arrival capacity estimation is proposed based on historical flow pattern behavior. The observed variability in throughput and terminal area delay performance emphasizes the importance of metroplex configuration predictability toward improved flow rate planning and ultimately better traffic regulation.

Characterization of blood flow patterns and endothelial shear stress during flow‐mediated dilation

Endothelial dysfunction is considered the first step in the development of atherosclerosis. Flow-mediated dilation (FMD) has been the most common assessment of endothelial function in research but it has failed in obtaining a widespread use in clinical settings due to a lack of standardization and a large inter-subject variability. Normalization of FMD to endothelial shear stress (ESS) has been proposed to solve its technical limitations. However, studies have not considered the characteristic of the blood flow during FMD under pulsatile conditions in their ESS estimations. A total of 26 young healthy subjects (15 females and 11 males) underwent FMD testing. Microhematocrit measurement was used to determine blood viscosity (μ). ESS was calculated by Womersley's approximation, ESS= μ*2K*Velocity/Diameter, where K is a function of Womersley's parameter (α). Blood flow patterns were determined by critical Reynolds number. Statistical analysis included repeated measures ANOVA to detect ESS differences during FMD until peak dilation. Significance was established at P≤0.05. The mean (SD) FMD% and time to peak dilation were 7·4 (3·1) % and 35 (9·3) seconds, respectively. ESS was significantly reduced during FMD until peak dilation (P<0·001). Turbulent blood flow was the only pattern observed until peak dilation in 96·15% of the sample. Peak FMD dilation in a young healthy population is triggered mostly by high-ESS under turbulent flow conditions. Due to the pulsatile nature of blood flow and the appearance of a turbulent pattern during FMD, ESS should be estimated by Womersley's approximation rather than Poiseuille's law.