Flow Velocity Patterns Research Articles

A Case Study of the Debris Flows Event in the Chalk Cliffs Basin, Colorado, USA: Numerical Simulations Based on a Multi-Phase Flow Model

Debris flows are among the severe gravity-driven mass phenomena that pose a significant threat to the environment and communities. Recent events and studies in the Chalk Cliffs basin in Colorado suggest that it is very susceptible to debris flow incidents that initiate from surface run-off, which involves significant entrainment of material along the hill slope and channel sediments. The entrainment of material along the flow makes these events destructive, with large travel distances s well as high velocity, flow pressure, kinetic energy, etc. This paper presents a case study of a debris flow event on 15 September 2009 based on a multi-phase flow model. The model provides the ability to investigate the effect of fluid and solid phases individually. Three sensitivity analyses are presented investigating the effect of bed roughness on solid and fluid phases separately, and also the effect of the entrainment of bed material. The findings demonstrate that the numerical model effectively replicates the observed field data, with the simulated peak discharge and runout distance closely aligning with the observed measurements. The analysis reveals that lower bed roughness promotes higher flow mobility and longer runout distances, while entrainment significantly influences flow height, velocity, and deposition pattern. Furthermore, the analysis highlights the dominant role of entrainment in debris flow evolution and emphasizes its importance in determining deposition and erosion patterns. These findings provide critical insights into the key processes of debris flows and could contribute to the development of accurate numerical models for debris flow events.

Impact of Rock Cuttings on Downhole Fluid Movement in Polycrystalline Diamond Compact (PDC) Bits, Computational Fluid Dynamics, Simulation, and Optimization of Hydraulic Structures

The flow occurring at the bottom of a polycrystalline diamond compact (PDC) drill bit involves a complex process made up of drilling fluid and the drilled rock cuttings. A thorough understanding of the bottom-hole flow conditions is essential for accurately evaluating and optimizing the hydraulic structure design of the PDC drill bit. Based on a comprehensive understanding of the hydraulic structure and fluid flow characteristics of PDC drill bits, this study integrates computational fluid dynamics (CFD) with rock-breaking simulation methods to refine and enhance the numerical simulation approach for the liquid–solid two-phase flow field of PDC drill bits. This study further conducts a comparative analysis of simulation results between single-phase and liquid–solid two-phase flows, highlighting the influence of rock cuttings on flow dynamics. The results reveal substantial differences in flow behavior between single-phase and two-phase conditions, with rock cuttings altering the velocity distribution, flow patterns, and hydraulic performance near the bottom-hole region of the drill bit. The two-phase flow simulation results demonstrate higher accuracy and provide a more detailed depiction of the bottom-hole flow, facilitating the identification of previously unrecognized issues in the hydraulic structure design. These findings advance the methodology for multiphase flow simulation in PDC drill bit studies, providing significant academic and engineering value by offering actionable insights for optimizing hydraulic structures and extending bit life.

Three-dimensional aortic arch geometry and blood flow in neonates after surgical repair for aortic coarctation.

Recurrent coarctation of the aorta (re-CoA) is a well-known although not fully understood complication after surgical repair, typically occurring in 10%-20% of cases within months after discharge. To (1) characterize geometry of the aortic arch and blood flow from pre-discharge magnetic resonance imaging (MRI) in neonates after CoA repair; and (2) compare these measures between patients that developed re-CoA within 12 months after repair and patients who did not. Neonates needing CoA repair, without associated major congenital heart defects, were included. Transthoracic echocardiography (echo) and 4D phase-contrast MRI were performed prior to discharge after CoA repair to assess 3D arch geometry, flow velocity and flow pattern in the distal aortic arch corresponding to the area at risk for re-CoA. Arch geometry was assessed by measuring angles of the aortic arch and its branches using 3D patient-specific geometries segmented from MRI. Continuous data are presented as median and interquartile range. The median age at CoA surgery was 9 days. Four out of the included 28 patients (14%) developed re-CoA within the first 12 months after surgery. Re-CoA was associated with repair technique (lateral thoracotomy 100% vs. 33%, p = 0.02), higher postoperative isthmic flow velocity by echocardiography (1.9 [0. 9] m/s vs. 1.25 [0.5] m/s, p = 0.04) and postoperative crenel aortic arch (100% vs. 21%, p = 0.007) with a larger distance between the first and last branching points (12.6 [3.1] mm vs. 7.3 [7.0] mm; p = 0.01). A smaller angle between the ascending aorta and the brachiocephalic artery (89 [58]° vs. 122 [37]°, p = 0.05) and between the proximal aortic arch and the left carotid artery (75° vs. 97 [37]°, p = 0.04), with a more pronounced caliber change between the ascending aorta and the proximal (1.85 vs. 0.86 [0.76]; p = 0.03) and distal aortic arch (2.19 [2.42] vs. 1.01 [0.94]; p = 0.03) were observed in re-CoA patients. Patients who developed re-CoA had more left-handed helical flow in systole (p = 0.045), more right-handed helical flow in diastole (p = 0.02), and less vortical flow (p = 0.05). Subtle changes in aortic arch geometry and flow pattern early after neonatal CoA repair may contribute to the risk of re-CoA.

Seepage monitoring at variable spatial positions under natural convection with active heating

Seepage monitoring at variable spatial positions under natural convection with active heating

Self-correction of the optical distortion effect of thermal plumes in particle image velocimetry

Optical distortion caused by changes in the refractive index of fluid flow is a common issue in flow visualization using techniques, such as particle image velocimetry (PIV). In thermally driven convection, this distortion can severely interfere with PIV results due to the ubiquitous density and, therefore, refractive index heterogeneity in the fluid. The distortion also varies spatially and temporally, adding to the challenge. We propose a composite filter, the shadow-affected PIV region filter, which combines a series of conventional image filters to address this issue, focusing on optical distortion of thermal plumes in laminar flow. We verify the effectiveness of the filter using both synthetic particle images created from ray tracing and real particle images from the laboratory. For the first time, we effectively mitigate the optical distortion from plumes while preserving the in-plane plume velocity and overall flow pattern, with the PIV data alone. Our filter is efficient and does not require additional measurements, expensive ray tracing, or a large dataset to begin with. It can be extended to separate the flow field and the effect of optical distortion in other fluid experiments when the two components are visually distinct. Additionally, this filter can serve as a baseline algorithm for comparison when developing more advanced methods like neural networks.

Study of pollutant transport under linear sorption in a groundwater reservoir

Abstract Pollutant dispersion in a porous medium can be modelled mathematically to forecast its concentration distribution profile. The governing equation of pollutant transport is modelled as a partial differential equation. Effects of sorption, zero-order production rate and first-order decay rate on pollutant transport are incorporated in the present study. The temporarily dependent pulse-type input source decaying exponentially is assumed at the origin of the domain. The solution of the proposed transport equation is derived by Laplace transform method for the respective time split domain. Matlab algorithm is developed to illustrate the obtained analytical solutions graphically for various hydrological input data. The pollutant distribution profiles in the medium are obtained for different times and porosities. The pollutant transport nature is examined for various forms of velocity flow pattern in presence and absence of input source. Also, the derived solution is compared graphically under special case with the existing solution and found the results with good agreement.

Determine velocity of fluid in curved micro channels fabricated with 3d printing (SLA)

The study investigated fluid dynamics in curved microchannels, exploring 3D printing parameters, channel geometry, and fluid properties, crucial for applications in medicine and energy. It highlighted the importance of microfluidics in handling small samples and enabling rapid analysis, stressing the need for precise measurement techniques to validate fluid velocity. Using 3D printing for microchannel design illustrated their utility, with microscopy aiding flow behavior comprehension. The research aimed to validate fluid velocity, covering technology analysis, microdevice design, fabrication, and measurement methodologies. It successfully fabricated microdevices confirming fluid movement via capillarity, revealing the relationship between channel radius and flow velocity. Distinct flow velocity patterns were observed, vital for design optimization. The study affirmed capillary flow as a spontaneous phenomenon, with fluid velocity variations along curved microchannels consistent with mass conservation principles in incompressible flows.

Hydrodynamic intensification and interfacial regulation strategy for the mixing process of non-Newtonian fluids

Hydrodynamic intensification and interfacial regulation strategy for the mixing process of non-Newtonian fluids

Numerical simulation of flow over short crested weirs - case study: Quarter-circular crested weir

Numerical simulation of flow over short crested weirs - case study: Quarter-circular crested weir

Hydrological control of the surging behaviour of the Ghujerab River Head Glacier, Karakoram (2019–2023): Insights from high-temporal-resolution remote sensing monitoring

Hydrological control of the surging behaviour of the Ghujerab River Head Glacier, Karakoram (2019–2023): Insights from high-temporal-resolution remote sensing monitoring

Dynamic behavior of mixed convection heat transfer among horizontal co-axial fixed pipes at varying temperatures: Efficiency of cylindrical heat sink

Dynamic behavior of mixed convection heat transfer among horizontal co-axial fixed pipes at varying temperatures: Efficiency of cylindrical heat sink

Effects of CO2 reaction-induced bubble proliferation on the dynamic conditions of stainless steel smelting molten pool

Effects of CO2 reaction-induced bubble proliferation on the dynamic conditions of stainless steel smelting molten pool

Experimental Study on Scouring and Silting and Channel Planning Based on the Entrance Area of Shenqiu Wharf

China has a vast territory and a long history of inland navigation. This paper is based on the Shaying River Shenqiu hub project, and a normal physical model with a geometric scale of 65 was established to simulate the characteristics of water and sediment in the entrance area of the project. By setting different working conditions and measuring and analyzing the velocity flow pattern of the wharf area, planning suggestions for the artificial channel with straight cut-off can be given. Simultaneously, the study simulates the natural sediment deposition state in typical years, observing changes in terrain and evaluating their impact on navigation, thereby validating the rationality of scouring and desilting processes. The research findings indicate that in the reconstructed river wharf’s entrance area, the flow velocity is low, and the flow pattern is stable, ensuring that the transverse flow velocities along the recommended route meet the requirements for vessel navigation. Post-scouring from the regulating gate discharge, downstream deposition decreases, with a sediment flushing efficiency reaching 68.5%. Under the specified conditions, the thickness of sediment deposition after scouring does not negatively affect the water level for ships entering or departing the wharf. The results of this study may offer valuable reference insights for the planning of artificial rivers in similar terrains.

A Comprehensive approach using CFD and GIS for dam break risk analysis: A case study on Nagarjuna Sagar earthen dam

This study presents a comprehensive approach utilizing Computational Fluid Dynamics (CFD) and Geographic Information Systems (GIS) to assess dam break risks with a specific focus on the Nagarjuna Sagar earthen dam. The study examines the numerical analysis of water flow dynamics resulting from a dam break. To depict this phenomenon, a two-dimensional numerical model employing the volume of fluid method was developed. The mathematical framework incorporates the Reynolds-averaged incompressible Navier-Stokes equations with the turbulent k-e model and was employed. The computational approach employed in this study is the SIMPLE algorithm. The CFD analysis involved meshing with 42,282 nodes and 41,680 elements, while boundary conditions included one velocity inlet and three pressure outlets open to the atmosphere. The flow was initialized with a 5 m dam site, scaled down at 1:10 (1 meter in the model representing 10 meters in reality). Data were collected for various time intervals (1s, 2s, 2.5s, 3s and 5s), The results of this study reveal the flow velocity patterns following dam break events for the specified time intervals. The outcomes are presented in terms of velocity magnitude vectors, static pressure, dynamic pressure, total pressure, turbulence kinetic energy, volume fraction contours and velocity magnitude profiles at different distances from the dam site (1m, 2m, 5m and 7m). A total of 250 iterations were performed to achieve these results, providing valuable insights into the dynamics of dam break scenarios. This research contributes to a better understanding of the potential consequences of dam failures and aids in improving risk assessment and mitigation strategies for dams.

Numerical simulation of velocity distribution and pollution transport in a two-stage channel with vegetation on a floodplain

Numerical simulation of velocity distribution and pollution transport in a two-stage channel with vegetation on a floodplain

Review on different shapes of spurs and their effects on channel morphology

Abstract In this paper, the significance of the shape of spurs on flow and bed morphology is understood, accompanied by an appeal to investigate alternative shapes like L-head, T-head spurs, and hockey-shaped spurs, which could offer considerable benefits for river management. The spurs with T-head shape are found to be more efficient in reducing the bed scouring of the channel relatively, although it depends on the orientation of the spur, location of installation, and shape of the channel. Furthermore, development of horseshoe vortex is found insignificant near the base of the T-head spur dike. T-head spurs could more effectively redirect flow and prevent erosion while L-head spurs may enhance riverbank stability. This highlights the need for more investigation into how different spur shapes collectively affect river morphology, flow velocity, and sediment transport patterns. Temporal variations in bed morphology, especially the scour depth and sediment transport dynamics near spur dikes, should also be investigated to understand their changing impact better. Finally, this study provides a complete summary of existing knowledge gaps and future research initiatives relevant to various shapes of spur dikes and their role in riverbank erosion management.

Optimization of hydraulic design of approach channel of spillway by hydraulic model studies

The approach channel is intended to divert the flow safely from its original course and the diversion may be intended towards spillway, power intake or any other hydraulic structure. The hydraulic design of the approach channel involves determining cross-section dimensions of the channel for the design flood at a given flow velocity, slope and shape or alternatively determining the discharge capacity for the given layout and cross-section dimensions. Proper alignment of approach channel minimizes the head loss by reducing the oblique flows. Sometimes, the spillway approach channel is submerged with unconfined boundaries, asymmetrical in layout. However, these conditions are site-specific. Hydraulic model studies play a substantial role in testing these kinds of layouts to find out an optimum layout. Studies have been carried out on a 1:140 scale model of the spillway to optimize the layout of an unconfined, unlined, asymmetrical, and submerged approach channel by the assessment of velocity profiles and flow pattern in the approach channel for different shaped layouts. Studies indicated that the efficient layout of the approach channel is governed by its maximum available width and straightforward approach, prevention of lateral inflows by the provision of additional embankments and provision of suitable length of the guide bund.

Abstract 15329: Echocardiographic Assessment of Cardiac Function in Preterm Miniature Pigs Supported With a Pumped Artificial Placenta

Introduction: Preterm birth is the leading cause of infant mortality and morbidity. Artificial placenta (AP) technology aims to support premature fetal piglets in an environment simulating intrauterine physiology to maintain fetal circulation and improve outcomes and survival. Hypothesis: We sought to understand the fetal cardiovascular physiology and mode of cardiac failure associated with a pumped extracorporeal membrane oxygenation circuit connected to the fetal circulation. Methods: Following umbilical cannulation, connection to a centrifugal pump and neonatal oxygenator and transition of preterm Yucatan miniature piglets to a fluid-filled biobag, echocardiographic studies measured ventricular function and fluid status including Dopplers, and strain analysis both prenatally and while maintained on the AP circuit. Results: AP fetuses (n=13; GA 102±4d; 616±139g; survival 46.4±46.8h) were tachycardic and hypertensive with supraphysiologic circuit flows initially. Strain analysis revealed significantly reduced RV strain rate within the first five hours of AP support compared to paired prenatal measurements (p=0.005) . Fetuses supported for <24h had significantly lower overall RV global longitudinal strain (p=0.001) than those surviving >24h. M-mode imaging revealed progressive cardiac hypertrophy with an increase in interventricular septum (p=0.03) and LV free (p=0.04) wall thickness from first to last measurements. Doppler measurements showed elevated peak flow velocity patterns in the MCA and reductions in MCA-PI from start to end of support (p=0.04) as well as compared to unpaired prenatal controls (p=0.03, p=0.001) . Imaging findings included ascites, skin edema, and dilated hepatic veins. Conclusions: AP fetuses exhibited signs of excessive volume and pressure loading resulting in impaired contractility, including supraphysiologic umbilical flows, reduced RV strain and strain rate, and evidence of elevated filling pressures. Myocardial hypertrophy and changes in cerebral perfusion indicated adaptation to increased afterload, potentially affecting cardiovascular and cerebrovascular development and leading to fetal deterioration. Further advancements in AP technology are necessary before clinical translation.

Numerical analysis of hemodynamic parameters in stenosed arteries under pulsatile flow conditions

Numerical analysis of hemodynamic parameters in stenosed arteries under pulsatile flow conditions

Hemodynamics in AVF over time: A protective role of vascular remodeling toward flow stabilization.

The mechanisms underlying vascular stenosis formation in the arteriovenous fistula (AVF) for hemodialysis (HD) remain mostly unknown. Several computational fluid dynamics (CFD) studies have suggested a potential role for unsteady flow in inducing intimal hyperplasia and AVF stenosis, but the majority of these observations have been limited to a single time point after surgical creation. The aim of the present study was to investigate the relation between hemodynamic conditions and AVF vascular remodeling through a CFD longitudinal study. Non contrast-enhanced MR images and Doppler Ultrasound (US) examinations were acquired at 3 days, 40 days, 6 months, 1 year, and 1.5 years after surgery in a 72-year male referred for native radio-cephalic AVF. Three-dimensional AVF models were generated and high fidelity CFD simulations were performed using pimpleFoam, setting patient-specific boundary conditions derived from US. Morphological and hemodynamic changes over time were then analyzed. Analysis of vessel morphology and hemodynamics during follow-up showed that the AVF had a successful maturation process, characterized by a massive arterial and venous dilatation within the 6 months after surgery, a corresponding increase in blood flow volume and important flow instabilities. Between 6 months and 1 year, a stenosis developed in the juxta-anastomotic vein and caused AVF failure at 1.5 years. The development of stenosis was paralleled by the regularization of blood flow velocity pattern and consequent decrease in the near-wall disturbed flow metrics. These results suggest that development of intimal hyperplasia and vessel stenosis, triggered by unsteady flow, could be the result of vascular inward remodeling toward regularization of turbulent-like flow.