Flow Motion Research Articles

Origin of Line Broadening in Fading Granules: Influence of Small-scale Turbulence

In the quiet region of the solar photosphere, turbulent convective motions of the granular flows naturally drive the subgranular-scale flows. However, evaluating such small-scale velocities is challenging because of the limited instrumental resolution. Our previous study, R. T. Ishikawa et al., found line-broadening events during the fading process of granules; however, their physical mechanism has remained unclear. In the present study, we observed the fading granules with the Hinode-SOT/SP and performed spectral line inversions. Moreover, we investigated the broadening events of synthesized spectra in fading granules reproduced by the MURaM simulation. Our results demonstrated that the small-scale turbulent motions are excited in the fading process, and such turbulent flows contribute to line broadening. The spectral line widths can be potential tracers of the photospheric turbulent flows.

The Upshots of Dufour and Soret in Stretching Porous Flow of Convective Maxwell Nanofluid with Nonlinear Thermal Emission

In this paper, the combined upshot of Soret and Dufoue of a convective Maxwell nanofluid on a porous perpendicular surface with nonlinear thermal emission was investigated. In the present work, the impact of permeable stretching sheet, nonlinear thermal emission, heat sour sink, Dufour and Soret effect, chemical reaction, Brownian motion and thermophoresis in a convective Maxwell nanofluid flow is widely discussed. The governing equations derived for the problem are highly nonlinear coupled partial differential equations. The governing equations were transformed into ordinary differential equations using Lie symmetry group alterations. The BVP4C MATLAB solver was employed to solve the ordinary differential equations numerically after validating the convergence of the method with existing results in the literature. The numerical results were established and discussed using tables and graphs. It was found that variations in porosity parameter (K), Dufour (Du) and Soret (Sr) improves velocity, temperature and concentration profiles respectively and the present of nonlinear thermal radiation and heat source emit more heat for the flow. Also, it is exciting to report that both porosity (K) and Dufour (Du) parameters has a strong impact on the flow of skin frictions, Nusselt number and Sherwood number. However, the current results may present applications in the areas of petroleum reservoir, heat exchangers, steel industries, cooling applications, nuclear waste disposal and so on.

Neutronics Analysis on High-Temperature Gas-Cooled Pebble Bed Reactors by Coupling Monte Carlo Method and Discrete Element Method

The High-Temperature Gas-Cooled Pebble Bed Reactor (HTG-PBR) is notable in the advanced reactor realm for its online refueling capabilities and inherent safety features. However, the multiphysics coupling nature of HTG-PBR, involving neutronic analysis, pebble flow movement, and thermo-fluid dynamics, creates significant challenges for its development, optimization, and safety analysis. This study focuses on the high-fidelity neutronic modelling and analysis of HTG-PBR with an emphasis on achieving an equilibrium state of the reactor for long-term operations. Computational approaches are developed to perform high-fidelity neutronics analysis by coupling the superior modelling capacities of the Monte Carlo Method (MCM) and Discrete Element Method (DEM). The MCM-based code OpenMC and the DEM-based code LIGGGHTS are employed to simulate the neutron transport and pebble movement phenomena in the reactor, respectively. To improve the computational efficiency to expedite the equilibrium core search process, the reactor core is discretized by grouping pebbles in axial and radial directions with the incorporation of the pebble position information from DEM simulations. The OpenMC model is modified to integrate fuel circulation and fresh fuel loading. All of these measures ultimately contribute to a successful generation of an equilibrium core for HTG-PBR. For demonstration, X-energy’s Xe-100 reactor—a 165 MW thermal power HTG-PBR—is used as the model reactor in this study. Starting with a reactor core loaded with all fresh pebbles, the equilibrium core search process indicates the continuous loading of fresh fuel is required to sustain the reactor operation after 1000 days of fuel depletion with depleted fuel circulation. Additionally, the model predicts 213 fresh pebbles are needed to add to the top layer of the reactor to ensure the keff does not reduce below the assumed reactivity limit of 1.01.

A novel investigation into time-fractional multi-dimensional Navier–Stokes equations within Aboodh transform

Abstract This investigation explores the analytical solutions to the time-fractional multi-dimensional Navier–Stokes (NS) problem using advanced approaches, namely the Aboodh residual power series method and the Aboodh transform iteration method, within the context of the Caputo operator. The NS equation governs the motion of fluid flow and is essential in fluid dynamics, engineering, and atmospheric sciences. Given the equation’s extensive and diverse applicability across several disciplines, we are motivated to conduct a thorough analysis to understand the complex dynamics associated with the nonlinear events it describes. For this purpose, we effectively handle the challenges posed by fractional derivatives by utilizing the Aboodh approach. This will enable us to obtain accurate analytical approximations for the time fractional multi-dimensional NS equation. By conducting thorough analysis and computational simulations, we provide evidence of the efficiency and dependability of the suggested methodologies in accurately representing the dynamic behavior of fractional fluid flow systems. This work enhances our comprehension of the utilization of fractional calculus in fluid dynamics and provides valuable analytical instruments for examining intricate flow phenomena. Its interdisciplinary nature ensures that the findings are applicable to various scientific and engineering fields, making the research highly versatile and impactful.

Modeling memory-enhanced stochastic suspended sediment transport with fractional Brownian motion in time-persistent turbulent flow

Modeling memory-enhanced stochastic suspended sediment transport with fractional Brownian motion in time-persistent turbulent flow

Understanding Patient Flow from the Perspectives of Patient Movement Experts

Background: Poor patient flow or patient movement through a healthcare organisation can lead to adverse outcomes for patients and organisational inefficiency. Many hospitals have addressed suboptimal patient flow by increasing resources, such as bed stock and staffing; however, this is an unsustainable approach. In determining the nature of poor patient flow issues, it is important to collect data from healthcare professionals who manage patient flow daily. Doing so provides insights into the current state of patient flow management in its entirety, whilst also helping with the development of sustainable solutions. Methods: Thirteen semi-structured interviews were conducted with healthcare professionals who were directly involved with patient flow at a referring hospital in Tasmania, Australia. Results: Using a thematic analysis method, four major themes were developed. The first major theme was: ‘managing patient flow’ which centered around known and unknown demands on bed availability. The second theme, ‘communication for decisions’, highlighted the essential role of communication in maintaining patient flow. The third theme, ‘tools as enablers and barriers, relates to the number of software programs which can both help and hinder patient flow. The final theme of ‘increasing complexity’ is related to an apparent trend towards greater numbers of patients requiring care of an increasingly specialised nature. Conclusions: The findings of this study provide great insights into patient flow issues, with potential solutions identified to address them.

MONGOLIA IN INTERNATIONAL FINANCIAL AND LOGISTICS CHAINS

The article is devoted to the methodological and practical aspects of assessing the specifics of developing countries, including Mongolia, in estimate of the performance of financial and logistics chains. The relevance and significance of the study is that decisions on the investment program (Vision 2050) are made on the basis of traditional assessments of investment projects, its’ economic and social effects. Based on a generalization of available information and data, the article presents the author’s approach to justifying the need to change traditional assessment methods. The necessity of taking into account in models the costs of diversification and forecasting changes in the place in value chains when implicit costs arise in the future has been proven. Ignoring the fact that the costs of international trade are passed on to consumers in small commodity economies often leads to recessions and the need for constant debt refinancing. The article examines the structure of Mongolia’s exports and imports not in traditional estimates, but from the position of influence on future growth of expenses in the absence of sources to cover them. Particular attention is paid to the growing inefficiency and irrationality of budget expenditures in the traditional forecasting of the effects and benefits from the implementation of the project. In relation to the research topic, the use of the terms «budget liquidity», «fictitious financial flows», «disguise of commodity flows» is justified. An approach to the classification of factors that distort the picture of the movement of financial and logistics flows from the point of view of influence on national economic interests is proposed. In conclusion, a conclusion is drawn about the possibility of practical application of the proposed approaches for the analysis of financial and logistics flows of other countries, as well as the existing assumptions in the application of this model.

Auto-Bäcklund transformation and exact solutions for a new integrable (2+1)-dimensional shallow water wave equation

Shallow water waves (SWWs) are often used to describe water flow and wave movement in shallow water areas. The article introduces a novel (2 + 1)-dimensional SWW equation. We prove that the equation is integrable and obtain an auto-Bäcklund transformation by truncating Painlevé expansion. Using the bilinear form of the equation, a new auto-Bäcklund transformation and some exact solutions are obtained. Besides, a convergent power series solution is derived using Lie symmetry method. These exact solutions can enrich mathematical modeling and help us understand nonlinear wave phenomena. Finally, conserved vectors are derived.

Study on gas–liquid–solid multiphase flow and erosion in ball valves

In industrial processes involving ball valves, gas–liquid–solid multiphase flows with continuous carrier and discrete particle phases are characterised by erosion challenges. These challenges reduce sealing performance and can lead to leakage and valve failure. To explore the characteristics of gas–liquid–solid multiphase flow and flow-induced erosion in ball valves, we conducted a combination of computational fluid dynamics numerical simulations and experimental testing. Results indicate that an increase in the gas content increases the flow coefficient, accelerates both liquid flow and particle movement and exacerbates erosion. In addition, particles are less concentrated in regions with higher gas concentrations. Erosion is primarily observed on the upstream surface and rear wall of the valve core as well as the upper side of the downstream pipeline. Severe erosion occurs more at smaller valve openings, and affected regions expand as the valve opening increases.

EFFECT OF BUILD POSITION ON SURFACE ROUGHNESS OF SLM PRINTED INCONEL 718

The present work investigates the variation of the surface roughness due to the build position of specimens with respect to the inert gas flow direction and re-coater movement direction. Selective laser melting (SLM) method was used to study this effect using Inconel 718 as workpiece material. A total of 21 samples were placed equidistant from each other on the built plate to observe the effect of gas flow and re-coater movement. The effect of these parameters on the printed samples was analyzed in terms of the profile surface roughness parameter such as Ra and Rz in the build direction. The result showed that samples placed near the gas inlet and the re-coater starting position had larger roughness as compared to the samples placed further from the gas inlet and re-coater end position. The result showed that the profile average roughness parameter values varied from Ra = 5.02 µm to 14.7 µm and profile maximum height surface parameter varied from Rz = 47.61 µm to 118.3 µm for all the printed samples. Surface topography of the samples was also studied which showed common printing defects such as cracks, micropores, local solidified melt pools, and dimples. The study opens an avenue to explore and optimize the placement of the printing sample on the build plate with respect to the inlet gas flow and re-coater movement directions for better surface roughness.

Coupled Modeling of Sea Surface Launch Flow and Multi-Body Motion

To simulate the launching process of missile complex flow, movement, and constraint states, a multifield coupling model is put forward based on a computational fluid dynamics (CFD) method. In this coupled model, a CFD method is used to solve the three-dimensional compressible transient flow, and the six-degree motion of the launching platform is considered, and the virtual contact method is used to deal with the constraint states of the guideway and the slider. The active force and moment are applied to the launching platform to simulate its rolling, pitching, and heaving motions under the 5-level waves. Collision detection is carried out through the minimum clearance distance between the slider and the guideway, and the contact force is handled by a modified Herz collision model. In the problem of launching a missile from the water surface, the change characteristics of the flow field, the load response characteristics, and the relative motion laws of the missile and the launching platform during the catapulting process are investigated. The results show that the motion laws of the projectile and the launch tube in the constrained direction are the same, and the established coupling model is able to simulate the launch separation process of the missile in the constrained state. In addition, the effect of wind load on the missile ejection process is analyzed using the coupled model.

Deep Learning Detection of Hand Motion During Microvascular Anastomosis Simulations Performed by Expert Cerebrovascular Neurosurgeons

Deep learning enables precise hand tracking without the need for physical sensors, allowing for unsupervised quantitative evaluation of surgical motion and tasks. We quantitatively assessed the hand motions of experienced cerebrovascular neurosurgeons during simulated microvascular anastomosis using deep learning. We explored the extent to which surgical motion data differed among experts. A deep learning detection system tracked 21 landmarks corresponding to digit joints and the wrist on each hand of 5 expert cerebrovascular neurosurgeons. Tracking data for each surgeon were analyzed over long and short time intervals to examine gross movements and micromovements, respectively. Quantitative algorithms assessed the economy and flow of motion by calculating mean movement distances from the baseline median landmark coordinates and median times between sutures, respectively. Tracking data correlated with specific surgical actions observed in microanastomosis video analysis. Economy of motion during suturing was calculated as 19, 26, 29, 27, and 28 pixels for surgeons 1, 2, 3, 4, and 5, respectively. Flow of motion during microanastomosis was 31.96, 29.40, 28.90, 7.37, and 47.21seconds for surgeons 1, 2, 3, 4, and 5, respectively. Hand tracking data showed similarities among experts, with low movements from baseline, minimal excess motion, and rhythmic suturing patterns. The data revealed unique patterns related to each expert's habits and techniques. The results showed that surgical motion can be correlated with hand motion and assessed using mathematical algorithms. We also demonstrated the feasibility and potential of deep learning-based motion detection to enhance surgical training.

Low-Reynolds-number droplet motion in shear flow micro-confined by a rough substrate

A three-dimensional spectral boundary element method has been employed to compute for the dynamics of the droplet motion driven by shear flow near a single solid substrate with a rough surface. The droplet size is comparable with the surface features of the substrate. This is a problem that has barely been explored but with applications in biomedical research and heat management. This work numerically investigated the influences of surface roughness features, such as the roughness amplitude and wavelength, on the droplet deformation and velocities. We observe that a greater amplitude or wavelength leads to larger variations in droplet velocity perpendicular to the substrate. The droplet velocity along the substrate increases when the amplitude is reduced or when the wavelength increases. The effects of capillary number and viscosity ratios have also been studied. The droplet deformation and its velocity increases as we increase the capillary number, while the viscosity ratio shows a non-monotonic influence on the droplet behavior. The predicted droplet behaviors, including deformation, velocities, and trajectories, can provide physical insight, help to understand the droplet behavior in microfluidic devices without a perfectly smooth surface, and contribute in the design and operation of those devices.

Three-dimensional modeling of hydro-morphodynamic characteristics of mining affected alluvial channel using TELEMAC and GAIA

In this numerical study, TELEMAC-3D and GAIA solvers were coupled to examine the three-dimensional (3D) flow and morphological changes in an alluvial channel due to sand mining. The 3D modeling approach enables a comprehensive analysis of the interactions between bed shear stress, velocity field, secondary flows, and turbulent kinetic energy that affect sediment transport processes near the mining pit. First, the numerical model was applied to two previous experimental studies on straight channels with mining and validated with their published data. Thereafter, model applications are demonstrated to a 180° curved channel with a mining pit at three different locations. The results indicate that the morphological changes in curved channels with a mining pit were relatively more asymmetrical in contrast to straight channels. The most severe bed degradation of 76.8% was observed at the outer bank downstream of the pit located at the end of 180° bend. The analysis of bed shear stress in the curved channel revealed higher values at the outer bank and lower values around the inner bank downstream of the pit location. Additionally, the presence of the mining pit had a significant impact on the structure and location of the secondary flow recirculation cell in the curved channel. The results indicate that turbulent kinetic energy increases significantly in the vicinity of the mining pit in both straight and curved channels. This increased turbulence due to bed topography may account for the enhanced secondary flow and sediment movement observed in the pit region.

Coupled Modeling of Computational Fluid Dynamics and Granular Mechanics of Sand Production in Multiple Fluid Flow

Summary Sand production is a significant issue in oil and gas fields with poorly consolidated formations, often involving the multiphase flow of reservoir fluids and solid particles. The multiscale mechanisms of sand production, particularly fluid flow and particle movement, remain poorly understood. This study investigates these mechanisms using a coupled computational fluid dynamics and discrete element method (CFD-DEM) modeling approach. Single and multiple fluid flows of water and heavy oil were simulated with increasing fluid injection velocities, leading to different sand production patterns. The simulation results were compared with experimental results from a large cylindrical specimen of weak artificial sandstone under similar loading conditions. The multiphase conditions created various localized flow and deformation patterns that influenced both fluid and solid production, resulting in shorter transient sand production periods. Microstructures and phenomena such as fingering and water coning were observed, associated with a critical flow rate below which oil displacement was uniform and no water breakthrough occurred. Higher fluid injection velocities and fluid viscosities resulted in greater drag forces, leading to progressive damage zones and explaining the occurrence of single or multiple staged sand production events. The evolution of the microscopic granular structure was visualized under the effect of transient sand production.

Morphological properties of two-dimensional and three-dimensional bedforms in open channel flow: A flume experiments study

Bedforms are formed by sediment particles under the action of flow, which in turn affect flow and sediment movement. However, the fundamental mechanisms behind the formation and development of bedforms under varying flow conditions, the interconnection between sediment particle movement and bed morphology development, as well as the influence of bedforms on flow and sediment transport, are still not well understood. In the current study, the moveable bed load transport flume experiments under different flow conditions were done, and the development processes of two-dimensional and three-dimensional dunes formed under different flow intensities were simulated. The detailed structure of the bedforms was measured by laser scanning technology, the characteristics of the bedforms were analyzed in detail, and the relations between the formation of the bedforms and the movement of sediment particles are discussed. The results found that the correlation coefficients of the longitudinal profile curve can serve as a quick reference for distinguishing two-dimensional and three-dimensional dunes. When the crestline ratio is used as the criterion for two-dimensional and three-dimensional dunes, the relative amplitude of the dune crestline and the included angle with the flow direction should also be comprehensively considered. The lee side angles of dunes calculated using the triangle generalization method and local section tangent method are compared and show that the values obtained by the former method are only about half of that of the latter. It is also found that the lee side angles of dunes are related to the dune height. The superimposed dunes generally exist in the downstream area of the stoss side of the dunes. The local bed slopes on the stoss side of the dunes show reverse slopes. The superimposed dunes improve the local bed height and further increase the reverse slope degree of the stoss side. A streamwise ridge is an important form located in the upstream area of the dunes stoss side, and they are symmetrically distributed on both sides. Multiple streamwise ridges divide the stoss side of the dunes into relatively independent movement areas, restricting the movement of sediment particles to specific regions. According to the distribution characteristics of bed morphologies, the effects of dunes on sediment particle movement and flow energy consumption are analyzed.

Asymptotic analysis of the 2D and 3D convective Brinkman–Forchheimer equations in unbounded domains

In this work, we carry out the asymptotic analysis of two- and three-dimensional convective Brinkman–Forchheimer (CBF) equations, which characterize the motion of incompressible fluid flows in a saturated porous medium. We establish the existence of a global attractor in both bounded (using compact embedding) and unbounded Poincaré domains (using asymptotic compactness property). In Poincaré domains, the estimates for Hausdorff as well as fractal dimensions of the global attractors are also obtained. We then show an upper semicontinuity of global attractors with respect to domains for CBF equations. We consider an expanding sequence of simply connected, bounded and smooth subdomains [Formula: see text] of the Poincaré domain [Formula: see text] such that [Formula: see text] as [Formula: see text]. If [Formula: see text] and [Formula: see text] are the global attractors of CBF equations corresponding to [Formula: see text] and [Formula: see text], respectively, then we show that for large enough [Formula: see text], the global attractor [Formula: see text] enters into any neighborhood [Formula: see text] of [Formula: see text]. The presence of the Darcy term in CBF equations helps us to obtain the above mentioned results in general unbounded domains also. Finally, we discuss the quasi-stability property of the semigroup associated with CBF equations in bounded domains and establish the existence of finite fractal dimensional global as well as exponential attractors.

Characteristics of debris flow development in Daxilada watershed and its hazard analysis on Lexi Expressway

The occurrence of frequent debris flow catastrophes in the mountainous regions of southwest China has necessitated the inclusion of debris flow disaster analysis and prevention as an essential component in the planning and construction of mountainous roadways. Daxilada watershed is located in the south of Mabian Yi Zuzizhixian, Leshan City, Sichuan Province, and the proposed Leshan-Xichang Expressway (Lexi Expressway) will pass through the upper reaches of Daxilada watershed. It is essential to consider that the presence of debris flows within the Daxilada watershed could have detrimental effects on the construction and functionality of the proposed Luoshanxi Bridge. This study examined the Daxilada watershed as a case study and analyzed the factors contributing to debris flow formation in the area. This analysis was based on field investigations, remote sensing interpretation, and experimental analysis. Additionally, the study utilized the Massflow software to simulate debris flow movement. It integrated the simulation results to determine the potential hazards the Daxilada Gully debris flow posed to the line project. This study found that Daxilada Gully meets debris flow formation conditions. The simulation results demonstrated that during the debris flow activity, there would be a maximum deposition depth of 2.1 m in the proposed Engineering Agency, which may lead to siltation and blocking disaster of the line project. Concerning the parameters related to the debris flow with a frequency of one in a hundred years, in conjunction with the outcomes obtained from numerical simulation, it would provide the design basis of the cross-flow cross-section of the proposed bridge. In a quantitative analysis of the blockage situation in the gully, debris flow deposits have the potential to cause damage to the line project. Debris flow deposits block the gully, but the risk of blockage is small. The study results have specific reference values for the debris flow prevention and control project of Lexi Expressway and offer valuable insights for the prevention and mitigation of similar disasters in relative projects.

Assessment of Microvascular Function Based on Flowmotion Monitored by the Flow-Mediated Skin Fluorescence Technique.

This review summarizes studies dedicated to the assessment of microvascular function based on microcirculatory oscillations monitored by the Flow-Mediated Skin Fluorescence (FMSF) technique. Two approaches are presented. The first approach uses oscillatory parameters measured under normoxic conditions, expressed as flowmotion (FM), vasomotion (VM), and the normoxia oscillatory index (NOI). These parameters have been used for the identification of impaired microcirculatory oscillations associated with intense physical exercise, post-COVID syndrome, psychological stress, and erectile dysfunction. The second approach involves characterization of the microcirculatory response to hypoxia based on the measurement of hypoxia sensitivity (HS). The HS parameter is used to characterize microvascular complications in diabetes, such as diabetic kidney disease and diabetic foot ulcers. Based on research conducted by the authors of this review, the FMSF parameter ranges characterizing microvascular function are presented. The diagnostic approach to assessing microvascular function based on flowmotion monitored by the FMSF technique has a wide range of applications and the potential to be integrated into widespread medical practice.

Development of heat and mass transfer modulus to Feflow code for calculation of brine loaded to permafrost ground

The article discusses the application of FreezeThaw75 module, developed by one of the authors to calculate heat and mass transfer taking into account water–ice and ice–water–water phase transitions. Numerical simulations are compared with the analytical solution and other software codes. The module was tested at one of the injection sites in Daldino-Alakitskii district of Yakutia. FreezeThaw75 module was developed in relation to Feflow v7.4–7.5 model environment. The module was tested on a model of brine injection into frozen rocks. The model simultaneously takes into account the movement of groundwater flow, heat and mass transfer and phase transitions. A feature of the calculations in the developed model is the consideration of large injected volumes of highly mineralized brines.It influences the degradation of permafrost and takes into account the cryohydrogeological conditions of the site. Brines are injected into permafrost rocks with a high absorption capacity especially in areas confined to zones of tectonic disturbances. The developed module can adjust the predicted potential of the operated injection sites. It can also act as an additional element of control over the injection process and the formation of an artificial aquifer in the permafrost rocks.