Regional Flow Research Articles

High-Resolution Tissue Doppler and Strain Imaging for Adult Zebrafish Myocardial Tissue Through Ultrafast High-Frequency Ultrasound Vector Doppler Estimation.

Zebrafish has been considered as an essential small-animal model for investigating the mechanism of heart regeneration. Due to the small size of zebrafish heart, high-frequency ultrasound (HFUS) imaging is often required for in vivo evaluations of its dynamic functions. Although commercial HFUS systems are available for myocardial velocity and strain measurement, only the outer myocardial region can be quantified due to the complex structure of zebrafish heart. In this study, a high-resolution 2-D myocardial tissue Doppler and strain imaging based on ultrafast HFUS imaging was developed for zebrafish heart imaging during heart regeneration. The cardiac flow region was first extracted to recognize the myocardial region, and the myocardial velocity and strain were then determined through vector Doppler estimation. Adult AB-line zebrafish was used for in vivo experiments, and cryoinjury was induced in the apical region of the heart. Both the myocardial velocity and strain of the whole ventricle after cryoinjury were directly visualized over 28 days. Myocardial velocity (during later diastolic motion) and strain, respectively, were significantly decreased (anterior wall: -2.0 mm/s and -3.3%; apical region: -2.0 mm/s and -4.5%; and posterior wall (PW): -1.7 mm/s and -4.3%) at the first three days after cryoinjury, which indicates weak myocardial beating due to heart injury. However, these all returned to the baseline values at 14 days after cryoinjury. All of the experimental results indicate that the proposed method is a useful tool for heart regeneration studies in adult zebrafish. In particular, it allows for the noninvasive evaluation of regional dynamic heart function.

Sealing efficiency performance of four different rim seals in turbine cavity

In modern aero-engine, the turbine rim seals whose purpose is to reduce the ingress are located in a complex flow region between the mainstream and secondary air flows. The sealing air discharged from the compressor of engine is used to purge turbine cavity. In order to examine the effects of ingress through four distinct rim seals, a one-stage test rig was used in the experiments presented in this work. At a Reynolds number of 5.16 × 105 in the mainstream and (0.85–2.13) × 106 in the rotational, the radial pressure distribution on the stator was determined. To assess flow characteristics and sealing efficacy, measurements of the swirl ratio and CO2 concentration were made. The reliability of turbine rim-seals is determined by the locations of the hook and teeth, as well as their effect on hot gas ingestion. To evaluate the performance of four types of seals: a datum double-rim seal and three derivatives with different clearances, the data are employed. Due to the inlet air position, the swirl ratio exhibited a pronounced inflection for all the rim seals. The sealing efficiency can be decreased by putting the hook closer to the rim or by taking the teeth out. Static pressure measurements in the turbine cavity indicate that the seal position has a significant impact. The analysis results revealed that the existence of slot vortex is beneficial to improving efficiency.

Exploring the enigmatic interplay between polymers and nanoparticles in a non-Newtonian viscoelastic fluid

Non-Newtonian fluids have variable viscosity in response to shear rate, and the presence of polymers and nanoparticles further modifies their flow characteristics. In this paper, the effects of polymers and nanoparticles on mass and heat transfer control, drag reduction, boundary layer flow development in a polymeric finitely extensible nonlinear elastic-Peterlin (FENE-P) fluid, and the significance of nanoscience in modern day life are discussed. We examine the behavior of polymer additives by utilizing a dispersion model in conjunction with the polymeric FENE-P model. Our work includes a comparison with Cortell’s [1] earlier work, which only looked at the behaviour of polymers inclusion into the base fluid. This research investigates numerically how the inclusion of polymers and nanoparticles into the base fluid reduces drag while increasing heat and mass transfer. The observed variations in skin friction, reduced Nusselt, and Sherwood numbers indicate an intriguing correlation between the rates of heat and mass transport and surface drag. More precisely, as the heat and mass transfer efficiency improve, the surface encounters less resistance, which is commonly referred to as drag. In summary, the research highlights the capability of polymers and nanoparticles to effectively modify fluid dynamics, minimize drag, and enhance mass and heat transfer inside the flow region.

Hydrodynamic instability of shear imposed falling film over a uniformly heated inclined undulated substrate

Linear and weakly nonlinear stability analyses of an externally shear-imposed, gravity-driven falling film over a uniformly heated wavy substrate are studied. The longwave asymptotic expansion technique is utilized to formulate a single nonlinear free surface deflection equation. The linear stability criteria for the onset of instability are derived using the normal mode form in the linearized portion of the surface deformation equation. Linear stability theory reveals that the flow-directed sturdy external shear grows the surface wave instability by increasing the net driving force. On the contrary, the upstream-directed imposed shear may reduce the surface mode instability by restricting the gravity-driving force, which has the consequence of weakening the bulk velocity of the liquid film. However, the surface mode can be stabilized/destabilized by increasing the temperature-dependent density/surface-tension variation. Furthermore, the bottom steepness shows dual behavior on the surface instability depending upon the wavy wall's portion (uphill/downhill). At the downhill portion, the surface wave becomes more unstable than at the bottom substrate's uphill portion. Moreover, the multi-scale method is incorporated to obtain the complex Ginzburg–Landau equation in order to study the weakly nonlinear stability, confirming the existence of various flow regions of the liquid film. At any bottom portion (uphill/downhill), the flow-directed external shear expands the supercritical stable zones, which causes an amplification in the nonlinear wave amplitude, and the backflow-directed shear plays a counterproductive role. On the other hand, the supercritical stable region decreases or increases as long as the linear variation of density or surface tension increases with respect to the temperature, whereas the sub-critical unstable region exhibits an inverse trend.

Hydrogeological conceptual model of Stampriet transboundary aquifer system in Southern Africa

Stampriet Transboundary Aquifer System (STAS) is shared between Botswana, Namibia and South Africa with massive utilization especially in Namibia. However, the understanding of the comprehensive hydrogeological framework of the aquifer system is limited. This study aimed to develop a comprehensive hydrogeological conceptual model of the aquifer system which mainly entailed 3D hydrostratigraphic modelling using Rockworks 3D geological modelling software, analysis of regional groundwater occurrence and flow system, sources and sinks, hydraulic parameters and definition of STAS boundaries. Six hydrostratigraphic units composed of four aquifers, including a new one (the Dwyka), and two aquitards were identified. Analysis of the regional groundwater flow system revealed that groundwater flows in two directions, indicating presence of a regional groundwater divide. 3D hydrostratigraphic geometry revealed that groundwater flow in STAS is influenced by topography but also by faults such as the Zoetfontein Fault, which displaces the pre-Kalahari rocks vertically creating a barrier to groundwater flow. Hydrostratigraphic and 3D geometry work also led to a 42% increase of the size of STAS compared to the boundary initially delineated by UNESCO. The proposed hydrogeological conceptual model forms a basis for development of numerical integrated hydrological model to simulate surface-groundwater interactions, regional groundwater flow and aquifer development potential.

A New Development of Cross-Correlation-Based Flow Estimation Validated and Optimized by CFD Simulation

The accurate measurement of mass flow rates is important in nuclear power plants. Flow meters have been invented and widely applied in several industries; however, the operating environment in advanced nuclear power plants is especially harsh due to high temperatures, high radiation, and potentially corrosive conditions. Traditional flow meters are largely limited to deployment at the outlet of pumps, on pipes, or in limited geometries. Cross-correlation function (CCF) flow estimation, on the other hand, can estimate the flow velocity indirectly without any specific instruments for flow measurement and in any geometry of the flow region. CCF flow estimation relies on redundant instruments, typically temperature sensors, in series in the direction of flow. One challenge for CCF flow estimation is that the accuracy of the flow measurement is mainly determined by inherent, common local process variation across the sensors, which may be small compared to the uncorrelated measurement noise. To differentiate the process variations from the uncorrelated noise, this research implements periodic fluid injection at a different temperature than the bulk fluid before the temperature sensors to amplify process variation. The feasibility and accuracy of this method are investigated through flow loop experiments and Computational Fluid Dynamics (CFD) simulations. This paper focuses on a CFD simulation model to verify the previous experimental results and optimize CCF flow estimation with different configurations. The optimization study is carried out to perform a grid search on the optimal location of the sensor pair under different flow rates. The CFD results show that the optimal sensor spacing depends on the flow rate being measured and provides guidance for sensor location implementation under various anticipated flow rates.

Geothermal energy appraisal and subsurface structural mapping of the Rafin Rewa warm spring region, Precambrian basement complex of Nigeria

This research work aims at evaluating the geothermal energy potentials of the Rafin Rewa warm spring (RRWS) of the Precambrian Basement Complex in Nigeria as an alternative energy source using integrated aeromagnetic geophysical techniques. Four aeromagnetic dataset were acquired, assemblage, analyzed, and interpreted using integrated geophysical processing techniques of spectral analysis and Euler deconvolution. Qualitative interpretation of the residual anomalous map reveals a distribution of positive anomalies (> 53 nT) majorly in the central and southeastern regions, which are traced to the granitic rocks, while the low anomalies (< − 1.5 nT) have been traced to the RRWS location emanating from the coastal plain sands of the Pliocene, Pleistocene, Oligocene, and Miocene ages. Quantitatively, the depth to the top (DTT) of the anomalous bodies reveals a depression that is almost intersecting with the Curie point depth (CPD) plot at the RRWS location, which indicates high heat flow in the RRWS region. The Spectral Analysis results reveal that the DTT and the CPD in this area ranges from 0.512 to 0.761 km and 6.504 to 10.582 km, respectively while the average CPD is 8.543 ± 0.325 km. It is observed that the DTT and CPD decrease as one move away from the RRWS region. The computed heat flow average was 160.76 ± 19.09 mW/m2 within the RRWS region. The Euler deconvolution result reveals the presence of geological structures, which were interpreted as faults and fractures. The major fractures trend in the east–west (E-W) directions, while the minor fractures trend northeast-southwest (NE-SW) directions. The geochemical result presented shows that iconic compositions impact the convective heat transfer processes associated with geothermal systems. It was conclusively believed that regions with comparable shallow CPDs could be viable for further geothermal energy investigations.

Numerical Investigation of the Performance of a Proton Exchange Membrane Water Electrolyzer under Various Outlet Manifold Structure Conditions.

The oxygen discharge process significantly affects the electrochemical performance of a proton exchange membrane water electrolyzer (PEMWE), which requires an optimal structure of the flow field implemented in the bipolar plate (BP) component. In this study, we numerically investigated the two-phase (liquid water and oxygen) flow in the PEMWE's channel region with different outlet manifold structures utilizing the volume of fluid (VOF) model. Then, the oxygen volume fraction at the liquid/gas diffusion layer (L/GDL) surface, i.e., the interface of the channel and L/GDL, obtained by the liquid water and oxygen flow model was incorporated into a three-dimensional (3D) PEMWE model, which made it possible to predict the influence of the outlet manifold structure on the multiple transfers inside the whole electrolyzer as well as the electrochemical performance. The results indicate that the existence of oxygen in the flow field significantly decreased the electrolyzer voltage at a fixed operation current density and deteriorated the uniform distribution of the oxygen amount, current density (corresponding to the electrochemical reaction rate) and temperature in the membrane electrode assembly (MEA), indicating that the rapid oxygen removal from the flow field is preferred in the operation of the electrolyzer. Moreover, slight increases in the width of the outlet manifold were helpful in relieving the oxygen accumulation in the anode CL and, hence, improved the electrolyzer performance with more uniform distribution characteristics.

Adaptive unified gas-kinetic scheme for diatomic gases with rotational and vibrational nonequilibrium

Multiscale nonequilibrium physics at large variations of local Knudsen number are encountered in applications of aerospace engineering and micro-electro-mechanical systems, such as high-speed flying vehicles and low pressure of the encapsulation. An accurate description of flow physics in all flow regimes within a single computation requires a genuinely multiscale method. The adaptive unified gas-kinetic scheme (AUGKS) is developed for such multiscale flow simulation. The AUGKS applies discretized velocity space to accurately capture the non-equilibrium physics in the multiscale UGKS, and adaptively employs continuous distribution functions following Chapman–Enskog expansion to efficiently recover near-equilibrium flow region in GKS. The UGKS and GKS are dynamically connected at the cell interface through the fluxes from the discretized and continuous gas distribution functions, which avoids any buffer zone between them. In this study, the AUGKS with rotation and vibration non-equilibrium is developed based on a multiple temperature relaxation model. The real gas effect in different flow regimes has been properly captured. To capture aerodynamic heating accurately, the heat flux modifications from the rotation and vibration modes are also included in the current scheme. Unstructured discrete particle velocity space is adopted to further improve the computational performance of the AUGKS. Numerical tests, including Sod tube, normal shock structure, high-speed flow around the two-dimensional cylinder and three-dimensional sphere and space vehicles, and an unsteady nozzle plume flow from the continuum flow to the background vacuum, have been conducted to validate the current scheme. In comparison with the original UGKS, the current scheme speeds up the computation, reduces the memory requirement, and maintains the equivalent accuracy for multiscale flow simulation, which provides an effective tool for nonequilibrium flow simulations, especially for the flows at low and medium speed.

Experimental Study on Heat Transfer Enhancement of 3D-Printed Mini Tubes Under Three Different Flow Directions

In this study, 864 heat transfer experimental data points and 216 pressure drop experimental data points were used to compare the heat transfer and friction factor behavior of 3D-printed and traditional tubes under uniform wall heat flux boundary condition. Experiments were conducted in the entire flow region that covers laminar, transition, and turbulent regions. The inside diameter of the test tubes is around 2 mm, and the average inside wall surface roughness for traditional and 3D-printed tubes is 2.211 μ m and 35.249 μ m , respectively. Comparing with the traditional tubes, in the upper transition and the turbulent regions, the Nusselt numbers and Colburn j -factors of the 3D-printed tube under three different flow directions were enhanced by an average of 52.67% and 51.59% respectively. The greater relative roughness of the 3D-printed tube enhanced the heat transfer but also increased the pressure drop significantly. The friction factors for the 3D-printed tube in these regions also increased by an average of 154.44% compared with the traditional tube. The results also show that the effect of different flow directions on heat transfer and pressure drop of the 3D-printed tube is insignificant relative to roughness. Moreover, the 3D-printed tube has an earlier transition compared with the traditional tube.

Exploring Apulia’s Regional Tourism Attractiveness through the Lens of Sustainability: A Machine Learning Approach and Counterfactual Explainability Process

Visitor attraction dynamics lead tourism industry paths. A complex artificial neural network model was built to predict the incoming tourism flow in the Apulia region of Southern Italy as a function of the heterogeneity of the tourism supply available in this area. Open data from the Regional Tourism Observatory were targeted. Information on the distribution of facilities and activities that attract regional tourist flows was collected and grouped by municipality. An artificial neural network model was built with total tourist attendance as the dependent variable and tourist attractions as regressors. The Root Mean Square Error (RMSE) was used to select the optimal model using the lowest value. The final model was run with a hidden layer consisting of three neurons and a decay value of 0.01. A Multi-Objective Counterfactual model (MOC) was then constructed using a randomly selected row of normalized data frame to validate a useful tool in increasing total tourist attendance by 20% over that of the randomly selected municipality. A Garson’s variables importance plot indicated natural landscapes such as beaches, sea caves, and natural parks have a primary role expressed in terms of variable importance in the AI algorithm when used as an innovative methodology for evaluating tourism flows in the Apulia region. A further MOC model built using a randomly selected row of normalized data frame showed convents, libraries, historical buildings, public gardens, and museums as the top five features most modified to improve total attendance in a randomly selected municipality. Use of AI modeling revealed that the implementation of nature-based solutions may speed up the flow of tourism in the Apulia region while also promoting sustainable social development.

Does Climate Variability Influence Internal Migration Flows in Senegal? An Empirical Analysis

This paper aims to estimate the total effect of climate variability on interregional migration flows in Senegal. We match regional climate data at origin, represented by normalised rainfall and normalised temperatures (maximum and minimum), with regional migration flow data from Senegal’s Agence Nationale de la Statistique et de la Démographie (ANSD) censuses to construct a panel database covering the five-yearly internal migration waves of 1976, 1988, 2001 and 2013. Using a gravity equation model where migration flows are explained by measures of climatic variability at origin, controlled for geographical, socioeconomic and demographic factors traditionally identified in the literature. Our results show that only negative precipitation anomalies at the origin area act as a push factor and accelerate emigration. In the predominantly agricultural regions, rainfall deficits appear, alongside traditional socioeconomic variables, as an additional significant factor shaping mobility across the country.

Numerical investigation on dynamic flow characteristics of methane condensation in microchannels

Microchannel condensers play an essential role in cryogenic two-phase heat management systems due to their efficient heat transfer characteristics. Thus, it is worth conducting an in-depth study on microscale condensation characteristics of cryogenic fluids. This paper delves into the flow condensation process of methane in microchannels. A two-dimensional transient model with high accuracy for cryogenic fluids has been developed by combining a self-defined program for the source term of the phase transition model. The model fully considers the boundary layer thickness and accurately explores the mesh accuracy. The complete condensation flow patterns are captured for various vapor quality, mass flux, and wall subcooling degrees. The injection flow is a unique flow regime for condensation in microchannels. The decrease in wall subcooling degree and increase in mass flux leads to the separation point at the neck of the injected flow moving towards the exit, while the annular flow region is expanding and the flow pattern transition is lagging. The mass flux improves the heat transfer coefficient more significantly at high vapor quality. During injection and bubble flow, the wall shear stress and local heat transfer coefficient are subject to bouncing and oscillations, which may induce fluctuations in the upstream annular flow. The prediction performance of six classical heat transfer correlations is evaluated. The results indicate that the Nie et al. correlation has the highest comprehensive prediction accuracy with MRD and MARD of -5.00 % and 15.83 %, respectively.

Hydrogeochemistry of aquifers in the northern portion of the Lagoa Santa Karst Environmental Protection Area and surroundings, state of Minas Gerais, Brazil

The studied region, located in the central part of Minas Gerais state, Brazil, encompasses the northern portion of the Lagoa Santa Karst Environmental Protection Area (APA) and adjacent areas to the west. It is notable for harboring important karstic aquifers and archaeological and paleontological sites of global significance. The research aims to define the key parameters that characterize the waters of the aquifers, quantifying their most frequent maximum and minimum concentrations. For this purpose, water sampling and hydrochemical analyses were conducted at 51 water points. Hierarchical clustering analysis facilitated the association of samples with aquifer units. Utilizing Piper and Stiff diagrams, boxplot graphs, and proportional symbol maps enabled the classification of water and the determination of its hydrochemical signatures. All sampled waters are bicarbonated, with 87% being calcic. Waters associated with metacalcareous rocks exhibit higher concentrations of calcium (Ca2⁺), bicarbonate (HCO₃⁻), electrical conductivity (EC), total dissolved solids (TDS), and hydrogenionic potential (pH) compared to waters associated with non-carbonate rocks. Waters from the Lagoa Santa Member differ from those of the Pedro Leopoldo Member by higher concentrations of Ca2⁺ and HCO₃⁻ and slightly lower concentrations of sodium (Na⁺), magnesium (Mg2⁺), and silica (SiO₄2⁻). Non-carbonate waters related to granite-gneisses differ from those associated with metapelites by slightly higher concentrations of potassium (K⁺), sodium (Na⁺), silica (SiO₄2⁻), and barium (Ba2⁺). Additionally, hydrochemical variations have been linked to the regional groundwater flow (from west to east). The results obtained have enabled advancements in the hydrogeochemical understanding of the study area and can be valuable for comparative studies in other karst regions, contributing to more effective water resource management aimed at environmental conservation and water sustainability, a growing global concern.

Using Expert Participation to Evaluate the Accuracy of Hand-Drawn Water-Table Maps.

Water-table maps are fundamental to hydrogeological studies and a manual, hand-drawn method is still commonly used to produce them. Despite this, the accuracy and variability of such maps have received little attention in international literature. In a unique experiment, 63 groundwater professionals drew water-table equipotential contours based on the same dataset of point measurements and were asked to infer flow directions and predict groundwater elevations at predefined locations. The root mean squared error (RMSE) for the average map calibration data was 10.5 m, which is accuracy comparable to numerical groundwater models. This study confirmed that to produce hand-drawn water-table maps, practitioners seek to not only fit the spatial data, but also to conform to their own cognitive model of hydrogeological concepts and processes. The calibration accuracy increased with experience; from a RMSE of 13.3 m for practitioners with 0-3 years of experience to a RMSE of 9.2 m for those with four or more years. Despite considerable variability in the style of the hand-drawn water-table maps, the maps were consistent in their representation of the dominant regional groundwater flow directions. There was less consensus, however, in predicting the direction of surface water-groundwater interaction for a stream reach. Hand-drawn water-table mapping remains useful and valid, especially as a starting point for hydrogeological conceptualization, yet further work is required to resolve issues around transparency, repeatability, and reproducibility.

Two-phase flow characteristics on porous layer in PEM electrolyzer under different flow channel layouts

As a promising green energy technology, low-temperature proton exchange membrane (PEM) electrolysis exhibits different reaction efficiencies and flow performances under various flow channel structures, but the specific impacts of these different layouts on performance are not well understood. To reveal the influence of the channel layouts, a two-phase PEM electrolysis model is established based on the experiment in this paper. Combing with flow characteristics, current density, and product distribution in the porous transport layers (PTLs) and catalyst layers (CLs), the results indicate that the flows from different directions have a significant impact on the electrolyzer. The vertical flow, perpendicular to the CLs, can greatly alleviate the product accumulation; meanwhile the transverse flow, parallel to the CLs, has a weaker but noticeable effect in gas ventilation. Partial gas will continue to accumulate in the region of weak vertical flow, especially at the end of the transverse flow. Except for the pin-type layout, other structures have a neat and orderly transverse flow within the porous medium, in the direction perpendicular to the flow channel's orientation. This flow pattern leads to product accumulation increasing along the exit direction, as well as product stagnation in the region of weak flow intensity. To facilitate the product discharge, a new flow channel layout, the pyramidal flow layout is proposed, which navigates the flow trend and enhances the convection near the exit. This new layout greatly evens out the current density and product concentration distribution.

Comprehensive examination of regional railway passenger behavior and dwell time components: Insights from video-based observations in Victoria, Australia

In understudied regional railway operations, this study explores passenger boarding and alighting patterns and how station design impacts them, particularly dwell times. Despite extensive metropolitan and suburban train research, regional railways have been overlooked. This study investigates regional rail passenger flow and dwell time to bridge this gap. This article studies dwell times and passenger boarding and alighting at two regional stations in Victoria, Australia, using CCTV data. The objective is to identify insights that might improve regional railway services' efficiency and user experience and advocate for sector-specific solutions. Analysis indicates distinct station boarding and alighting features, highlighting the discovery of the ‘blinded phenomenon’ for train conductors particularly in the afternoon peak (PMP). The results of the study showed that PMP services, which prioritise alighting passengers, had higher dwell times than the morning peak (AMP) services, which emphasise boarding passengers. Obstructed views make it difficult for train conductors to monitor passenger alighting, prolonging dwell times. Better human resource strategies, artificial intelligence for crowd surveillance, and strategic CCTV system deployment to streamline operations and improve passenger experience on regional railways are proposed in the paper, laying the groundwork for future research and operational changes in this vital transportation sector.

Transient energy transfer and cascade analysis for stratified turbulent channel flows

A comprehensive and fine-grained transient analysis of the kinetic budget equation in the spectral and spatial domains for channel flow subjected to stable stratification is performed, through a series of large eddy simulations (LES) at a bulk Reynolds number of 2200 and for Froude numbers of 0.5, 2.0, 4.5 and 6.8, thereby covering a range of stratification strengths from high to low. The dynamic Smagorinsky eddy viscosity-based sub-grid scale (SGS) model is used for closure. Validation of the methodology is carried out by comparing the turbulent flow LES results to previously published channel flow results. The analysis is focussed on the effect of stratification on the energy cascade process of an initially turbulent flow in a channel configuration. The terms in the kinetic budget equation, in the homogeneous and inhomogeneous directions, are compared for different Froude numbers to assess the effects of weak and strong stratification on turbulent statistics. Transient results are plotted to highlight the role played by different terms in the budget equation and to understand the formation of the gravity waves in the core or outer regions of the wall-bounded flow in the presence of stratification. The energy cascade reveals some interesting observations about the functions of viscous diffusion, pressure diffusion, and inhomogeneous energy transfer in the initial phase of the development of flow, which in turn helps to explain the stationary waves observed in the presence of strong stratification.

Effect of multiscale metro network-wide attributes on peak-hour station passenger and flow balancing

Analyzing the balance of station passenger and passenger flow is essential for understanding jobs-housing balance and built environment in station areas and network-wide range as well as for enhancing the efficiency of urban rail transit operations. Taking the Shanghai rail transit network as a case study, this paper defines the Multiscale Subnetwork (MSSN) based on a specific spatial scope. By extracting the network features and built-environment elements of the stations and the MSSN, this study analyzes the factors affecting the peak-hour station passenger and the imbalance of regional network passenger flow. The research suggests that the small MSSN analysis, within 6-8 km from a station, can provide valuable results from a network-wide perspective, rather than solely focusing on individual station areas or the entire network. The regional attributes of jobs-housing balance and the transportation conditions in the MSSN range have great impact on both station passengers and flow imbalance. This research provides theoretical insights for urban planners and policymakers to formulate effective strategies for urban rail transit networks.

Turbulent Channel Flow Diagnostics By Means Of Shake-The-Box (STB): Flow Structures And Sublayer Profiles

Time-resolved Shake-the-Box (STB) experiments have been conducted in the channel-flow facility at the Institute of Fluid Mechanics (ISTM) at f = 30 kHz repetition rate to study the near-wall velocity field at a viscous Reynolds number of Reτ = 350 (centerline velocity Ucl = 8.4 m/s, channel half-height h = 12.6 mm, viscous unit δv ≈ 36 μm) to testify the STB method for the applicability to provide high-resolution velocity information of the given flow field including the sublayer region of the channel flow. In addition to the extraction of Lagrangian particle tracks and corresponding Eulerian iso-surfaces of vortical structure the major emphasis of the study centers around an evaluation of the resulting near wall velocity profile. Particularly, it is discussed how the choice of data-processing steps and strategies affects the resulting velocity estimates in the immediate vicinity of the wall, where the major impact for the current study has been identified to result from image-arithmetic efforts during data pre-processing. The achieved results are discussed and further compared with direct numerical simulations (DNS) of similar Reτ and earlier experimental efforts at ISTM of the same flow configuration by means of stereoscopic particle image velocimetry (stereo PIV) and a laser-Doppler velocimetry profile sensor (LDV-PS). Finally, future perspectives of the experimental efforts for near-wall shear flow measurements are outlined on the grounds of the achieved insights.