Duct Flow Research Articles

Successful probing of Congenital Nasolacrimal Duct Obstruction on 11 years old child: A case report

Introduction : Congenital nasolacrimal duct obstruction (CNLDO) is a common cause of epiphora in infants; its prevalence rate of 5% to 20%, although only 2–6% will need intervention. The pathogenesis involves an imperforate membrane of the nasolacrimal duct but it may involve bony abnormalities and narrowing of the lacrimal drainage system.
 Case Illustration : An 11-year-old boy came to the hospital with complaints of a watery and excreted eye since he was born. On the dye disappearance test the result is +4. The patient was decided to have probing procedures. There was positive dye flow in the nasolacrimal duct after probing and irrigation with saline and dye. One week after the probing procedure, dye disappearance test was performed and the result is negative. Patients also no longer complain of watery and sticky eyes.
 Discussion : The management of CNLDO remains controversial. Probing can be used as a primary treatment for children <36 months of age, where success rate of 78–93% can be achieved. For older children success rate is even less. Studies on older children between 25 and 60 months have shown failure rates as high as 28%. The prevalence of complex obstruction in children between 49 and 60 months was 43% with a success rate of only 33% on probing.
 Conclusion : Appropriate time for probing the CNLDO is still under debate. The high success rate of probing in patients older than 2 years old confirm that the first intervention could be probing before considering complex intervention.

Successful probing of Congenital Nasolacrimal Duct Obstruction on 11 years old child: A case report

Introduction : Congenital nasolacrimal duct obstruction (CNLDO) is a common cause of epiphora in infants; its prevalence rate of 5% to 20%, although only 2–6% will need intervention. The pathogenesis involves an imperforate membrane of the nasolacrimal duct but it may involve bony abnormalities and narrowing of the lacrimal drainage system.
 Case Illustration : An 11-year-old boy came to the hospital with complaints of a watery and excreted eye since he was born. On the dye disappearance test the result is +4. The patient was decided to have probing procedures. There was positive dye flow in the nasolacrimal duct after probing and irrigation with saline and dye. One week after the probing procedure, dye disappearance test was performed and the result is negative. Patients also no longer complain of watery and sticky eyes.
 Discussion : The management of CNLDO remains controversial. Probing can be used as a primary treatment for children <36 months of age, where success rate of 78–93% can be achieved. For older children success rate is even less. Studies on older children between 25 and 60 months have shown failure rates as high as 28%. The prevalence of complex obstruction in children between 49 and 60 months was 43% with a success rate of only 33% on probing.
 Conclusion : Appropriate time for probing the CNLDO is still under debate. The high success rate of probing in patients older than 2 years old confirm that the first intervention could be probing before considering complex intervention.

Analytical solution for the magnetohydrodynamic duct flow with slip condition on the perturbed boundary

We consider the flow of an electrically conducting fluid in a rectangular duct driven by the pressure gradient and under the action of a transverse magnetic field. A small boundary perturbation is applied on the cross-section of the duct and the hydrodynamic slip condition is imposed on this rough part of the boundary. A higher-order effective model is proposed via asymptotic expansion technique in the form of the explicit formulae for the velocity and the induced magnetic field. Based on the analytical results, numerical examples are provided indicating the nonlocal effects of the slip condition and the perturbed boundary.

Early Echocardiographic Predictors of Eventual Need for Patent Ductus Arteriosus Treatment: A Retrospective Study.

Hemodynamically significant patent ductus arteriosus (hsPDA) in preterm neonates is associated with end-organ injury including intraventricular hemorrhage. Early treatment may reduce morbidities but may result in overtreatment. This study aimed to examine the association between commonly obtained echocardiographic markers within the first 12 hours of life and eventual treatment of an hsPDA. Patients with <32 weeks' gestational age had blinded echocardiograms done within the first 12 hours of life as part of research protocols. Subsequent treatment of the patent ductus arteriosus (PDA) was determined by the clinical team independent of echocardiogram results. t-tests and chi-square tests were done for continuous data and categorical outcomes. A receiver operating curve was created to optimize cutoff values. Among 199 neonates studied (mean time of echocardiogram 6.7 h after birth), those needing PDA treatment had higher left ventricular output (LVO), right ventricular output (RVO), and superior vena cava (SVC) flow (p-values 0.007, 0.044, and 0.012, respectively). Cutoffs for predicting PDA treatment were LVO > 204 mL/kg/min (63% sensitivity, 66% specificity), RVO > 221 mL/kg/min or SVC flow > 99 mL/kg/min (sensitivities 70 and 43%, specificities 48 and 73%, respectively). Preterm neonates with higher markers of cardiac output in the first 12 hours of birth later required PDA treatment. These data are the first to use standard cardiac output measures in the first 12 hours of life to predict the need for future PDA treatment. Further prospective studies will need to be performed to corroborate these associations between echocardiographic markers and clinical outcomes/morbidities. · Early diagnosis of hsPDA may prevent severe morbidity and death.. · There are echocardiographic markers beyond duct size and flow direction that may aid early diagnosis.. · Cardiac output markers within the first 12 hours of life may predict need for treatment of hsPDA..

Data-driven turbulence modeling for fluid flow and heat transfer in peripheral subchannels of a rod bundle

This study presents a comparison of the performance of machine learning (ML) techniques, specifically multi-dimensional gene expression programming (MGEP), tensor basis neural network (TBNN), and also proposes a novel universally interpretable machine learning architecture to model the turbulent scalar flux (UIML-s) to enhance turbulence models for fluid flows at different Prandtl numbers in channels with complex shapes of walls in the channel cross section. In particular, peripheral subchannels of rod bundles are of primary interest. However, the accuracy of mean velocity and scalar distributions predicted by commonly used turbulence models still poses a challenge compared to data extracted from high-fidelity eddy-resolving numerical simulations, particularly for engineering applications involving complex geometry flows. In the present study, by utilizing an explicit algebraic expression for the nonlinear Reynolds-stress term obtained through both the evolutionary MGEP optimization and TBNN, the secondary flow structure has been adequately predicted in the cross-wise mean velocity distributions in the square duct and the rectangular channel with three longitudinal rods. This structure is also observed in the data from the concurrent runs performed by direct numerical simulation (DNS) but is completely absent in the results produced by a baseline Reynolds-averaged Navier–Stokes (RANS) closure, which employs the linear eddy viscosity model for the Reynolds stress tensor. Comparison of MGEP and TBNN has shown their nearly equal performance in a square duct flow; however, MGEP works better for the more complex geometry channel with three rods. Furthermore, based on the velocity field produced by the RANS-MGEP model, the ML modification of the gradient diffusion hypothesis, integrated into the aforementioned novel RANS-ML model called as UIML-s, significantly improves the mean scalar distributions in a flow with three bumps serving as a prototype for the peripheral subchannel of rod bundle. The normalized root mean squared error decreases from 13.5% to 7.6%, bringing the predicted distributions closer to the DNS data, particularly in the near-wall region. Another approach, MGEP-s, also yields the acceptable results, which are nearly identical to those from UIML-s. These findings highlight the potential of using data-driven calibration of turbulence models with nonlinear closures to enhance the predictability for RANS simulations of fluid flows, heat, and mass transfer in channels with complex geometry.

The effects of boundary roughness on the MHD duct flow with slip hydrodynamic condition

In this paper we present the analytical study of the magnetohydrodynamic (MHD) flow through a rectangular duct driven by the pressure gradient and under the action of the transverse magnetic field. Motivated by various MHD applications in which hydrodynamic slip naturally occur, we prescribe the slipping boundary condition on the upper boundary which contains irregularities as well. Depending on the period of the boundary roughness, we derive three different limit problems by using rigorous analysis in the appropriate functional setting. This approach also enables us to determine the relative contribution of the MHD effect and the slip itself in the governing coupled system satisfied by the velocity and induced magnetic field.

The value of wake steering wind farm flow control in US energy markets

Abstract. Wind farm flow control represents a category of control strategies for achieving wind-plant-level objectives, such as increasing wind plant power production and/or reducing structural loads, by mitigating the impact of wake interactions between wind turbines. Wake steering is a wind farm flow control technology in which specific turbines are misaligned with the wind to deflect their wakes away from downstream turbines, thus increasing overall wind plant power production. In addition to promising results from simulation studies, wake steering has been shown to successfully increase energy production through several recent field trials. However, to better understand the benefits of wind farm flow control strategies such as wake steering, the value of the additional energy to the electrical grid should be evaluated – for example, by considering the price of electricity when the additional energy is produced. In this study, we investigate the potential for wake steering to increase the value of wind plant energy production by combining model predictions of power gains using the FLOw Redirection and Induction in Steady State (FLORIS) engineering wind farm flow control tool with historical electricity price data for 15 existing US wind plants in four different electricity market regions. Specifically, for each wind plant, we use FLORIS to estimate power gains from wake steering for a time series of hourly wind speeds and wind directions spanning the years 2018–2020, obtained from the ERA5 reanalysis dataset. The modeled power gains are then correlated with hourly electricity prices for the nearest transmission node. Through this process we find that wake steering increases annual energy production (AEP) between 0.4 % and 1.7 %, depending on the wind plant, with average increases in potential annual revenue (i.e., annual revenue of production, ARP) 4 % higher than the AEP gains. For most wind plants, ARP gain was found to exceed AEP gain. But the ratio between ARP gain and AEP gain is greater for wind plants in regions with high wind penetration because electricity prices tend to be relatively higher during periods with below-rated wind plant power production, when wake losses occur and wake steering is active; for wind plants in the Southwest Power Pool – the region with the highest wind penetration analyzed (31 %) – the increase in ARP from wake steering is 11 % higher than the AEP gain. Consequently, we expect the value of wake steering, and other types of wind farm flow control, to increase as wind penetration continues to grow.

Physically Realistic Inlet-Velocity Profiles in Duct Flows

A uniform inlet velocity profile is widely used in the numerical simulations of fluid flow and heat transfer in ducts for both incompressible and compressible flows. In incompressible flows, the calculated fluid pressure at the inlet edge is extremely high and affects the calculation of the average pressure. In compressible flows, the fluctuation of pressure in the flow direction results in the fluctuation in the velocity. This has motivated this study to numerically investigate a physically realistic velocity profile at the inlet of a pipe rather than using a uniform velocity profile. The numerical simulations were based on the control volume-based power law scheme and the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The continuity and momentum equations for a flow in a pipe with the rounded inlet corner were solved to obtain a physically realistic inlet velocity profile. The obtained inlet velocity profile was expressed by a simple expression in the range of Reynolds number from 100 to 2000. Using this velocity profile, both the incompressible and compressible flows in a pipe were numerically investigated. The results resolved the previously observed inconsistencies in the pressure that were previously observed in the numerical simulations with uniform inlet velocity profiles.

Effects of electromagnetic compound field on the macroscopic morphology of laser cladding

To enhance the controllability of the molten pool morphology, a directional Lorentz force is produced within the molten pool by synchronously coupling a steady electric field and magnetic field during the laser cladding process. A 2D numerical model of the molten pool considering solid–liquid phase change, heat transfer, fluid flow, deformed geometry and electromagnetic induction is established. The experimental and simulation results demonstrate that the magnetic or electrostatic field has negligible effects on the molten pool shape. The compound electromagnetic field (simply as a compound field) that generates a downward Lorentz force significantly impacts the molten pool height, and wetting angle. As revealed by the observation of the molten pool forming process, it is found that the downward Lorentz force disrupts the force balance of the molten pool, which leads to the outward expansion of the fluid due to an increased pressure difference. As a consequence, the height of the molten pool decreases. Meanwhile, the employment of a magnetic field results in a significant increase in the viscous resistance at the solidification interface. The fluid is accumulated at the bottom of the molten pool, which increases the wetting angle. Additionally, since this approach can produce a steady volume force similar to gravity, it can be used in a weightless environment, such as in a space station, thus significantly improving the process stability.

Evaluating the effect of action-like video game play and of casual video game play on anxiety in adolescents with elevated anxiety: protocol for a multi-center, parallel group, assessor-blind, randomized controlled trial

BackgroundAdolescence is a critical period for the onset and maintenance of anxiety disorders, which raises the importance of intervening early; one possibility of doing so is via digital interventions. Within that research field, at least two important research paths have been explored in the past years. On the one hand, the anxiolytic effect of casual video games has been tested as such gaming activity may distract away from anxious thoughts through the induction of flow and redirection of attention toward the game and thus away of anxious thoughts. On the other hand, the bidirectional link between weak attentional control and higher anxiety has led to the design of interventions aiming at improving attentional control such as working memory training studies. Taking stock that another genre of gaming, action video games, improves attentional control, game-based interventions that combines cognitive training and action-like game features would seem relevant. This three-arm randomized controlled trial aims to evaluate the feasibility and the efficacy of two video game interventions to document how each may potentially alleviate adolescent anxiety-related symptoms when deployed fully on-line.MethodsThe study aims to recruit 150 individuals, 12 to 14 years of age, with high levels of anxiety as reported by the parents’ online form of the Screen for Child Anxiety Related Disorders questionnaire. This trial contrasts a child-friendly, “action-like” video game designed to improve attentional control abilities in a progressive and stepwise manner (Eco-Rescue), a casual puzzle video game selected to act as a positive distraction tool (Bejeweled) and finally a control group with no assigned training intervention to control for possible test-retest effects (No-training). Participants will be assigned randomly to one of the three study arms. They will be assessed for main (anxiety) and secondary outcomes (attentional control, affective working memory) at three time points, before training (T1), one week after the 6-week training (T2) and four months after completing the training (T3).DiscussionThe results will provide evidence for the feasibility and the efficacy of two online video game interventions at improving mental health and emotional well-being in adolescents with high levels of anxiety. This project will contribute unique knowledge to the field, as few studies have examined the effects of video game play in the context of digital mental health interventions for adolescents.Trial registrationThe trial is registered on ClinicalTrials.gov (NCT05923944, June 20, 2023).

Fractal patterns in fluid flows: A radial basis pseudospectral analysis of CuO-EG water nano, Saffman dusty, and plain Newtonian fluids in immiscible layers of a horizontal channel

Nano and dusty fluids provide new possibilities to improve energy transfer efficiencies. Motivated by immiscible fluids duct flow framework in the filtration of hydrocarbon materials, the objective of this manuscript is to present the numerical study of three immiscible fluids namely, copper oxide-ethylene glycol (CuO-EG) water nano, Saffman dusty, and plain Newtonian fluids in the horizontal channel. For the formulation of the mathematical model, the dusty fluid is positioned between the immiscible layers of the nanofluid and Newtonian fluid. The interface between the immiscible fluids is continuous and non-deformable in nature. The flow is driven by an externally time-dependent pressure gradient. The novel radial basis function pseudospectral (RBFPS) method is employed to solve the governed partial differential equations, and the resulting outcomes are compared with cubic B-spline differential quadrature and finite difference method. The impact of several crucial fluid parameters, comprising the volume percentage of CuO nanoparticles, the dust particle concentration parameter, and various others on velocity profiles, are presented graphically. It is observed that despite being present only in the lower zone, the CuO nanoparticles have an impact on the flow velocities in other zones also. The fluid and particle velocities decrease as the volume fraction of CuO increases.

Mirror-based multimodal straightforward method for impedance eduction using a zigzag array

The Mirror-based Multimodal StraightForward Method (MM-SFM) is proposed herein to realize accurate and reliable liner impedance eduction covering the wide frequency range of aeroengine fan noises. It adopts a novel zigzag array in the flow duct, and unfolds them by a coordinate transformation into a mapping diagonal array in an extended duct, which can increase the array transverse spacing Δz considerably. Then, it invokes the M-SFM incorporating the trust-region and extended Prony's algorithms, to decompose the three-dimensional multimodal aeroacoustic field and educe the impedance. A parametric study based on the Monte-Carlo uncertainty analysis is conducted through finite-element numerical experiments on a 51 × 51 mm2 flow duct, to survey the method performance under random perturbations. It indicates that, the educing accuracy and reliability are promoted by increasing Δz or the axial spacing Δx properly, and the decomposed-mode number M×N=10 is appropriate herein. In our studied cases, using the recommended array of Δz=25.5mm and Δx=22mm locating at the nodes of transverse mode m = 2, the MM-SFM generally produces accurate averaged educed impedances in a considerably extended frequency range from 100 Hz up to nearly 10 kHz, and has small educing uncertainties at most absorptive frequencies and thus a good reliability.

Flow in ducts with varying cross-sectional area and friction

Flow in ducts with varying cross-sectional area and friction

Particle transport in turbulent square duct flows with a free surface

Direct numerical simulation combined with a one-way coupled Lagrangian particle tracking technique is employed to investigate dilute particle-laden turbulent flows in open square ducts with a free surface. The focus is on examining the influence of the mean cross-stream secondary flow on particle transport near the wall, free surface, and across the duct cross section. Based on the duct half-width and mean friction velocity, a shear Reynolds number of Reτ = 300 is considered, with the corresponding particle Stokes numbers ranging from St+ = 0.31 to 260. The results reveal that particle concentration near the sidewalls is lower than that near the bottom wall, and the minimum particle concentration is observed at the free surface. Along the bottom wall centerline orientated upward, particle concentration gradually decreases. An exception to this is in the vicinity of the free surface where a slight increase is observed for the heavier particles (St+ ≥ 25), and the amplitude of this increase gradually declines as the Stokes number increases. In the streamwise direction near the free surface, heavier particles tend to preferentially concentrate in regions where the instantaneous transverse secondary flow velocity is negative. As the Stokes number increases, the position of the maximum streamwise velocity for heavier particles is closer to the free surface, and the rotation centers of inner and outer secondary particle motions gradually disappear. The streamwise root mean square velocity for the lightest St+ = 0.31 particles is higher than that for particles with higher inertia in the middle region of the free surface.

An Overview on the Dispersion of Steel Fiber in Ultra-High-Performance Concrete

Abstract Ultra-high-performance concrete (UHPC) is widely recognized for its high toughness, which is directly affected by the dispersion of steel fiber and its loading mode. To investigate the reinforcement effect of steel fiber, this paper summarizes the influencing factors, evaluation methods, and theoretical models of steel fiber dispersion in UHPC. First, the results reveal that a scientifically designed mixture can reduce the cost of steel fiber dosage in UHPC and improve fiber dispersion by adjusting matrix rheological properties. The optimum plastic viscosity of the slurry should range from 30 to 80 Pa·s for achieving the best fiber dispersion effect. Second, during slurry placement, the orientation of fibers in UHPC can be improved by up to 80 % through flow induction and the wall effect, which increases the bending strength, tensile strength, and toughness of UHPC matrix by 5–67 %, 30–90 %, and 13–200 %, respectively. Moreover, although the dispersion of fiber in two-dimensional space has been extensively studied, further characterization in three-dimensional space is required. Lastly, some theoretical simulation results have been achieved on fiber orientation, but factors such as aggregate or reinforcement must be considered.

CFD simulation of methane circulation dynamics in a ventilation installation's tubing

Reducing the risk of occurrence of phenomena such as explosions, as a result of the untimely penetration of a certain amount of explosive gases, inside a ventilation installation, is a priority, regarding the health and safety of workers, material assets and the negative influence on the environment, due to the possible problems caused by the occurrence of explosive atmospheres, formed by mixing air with gases, vapors, mists and combustible dusts. The main measure to prevent explosive atmospheres is to provide adequate ventilation in closed or semi-closed industrial and non-industrial premises. In order to avoid dangerous situations at the level of poorly ventilated ventilation installations where explosive atmospheres can occur, it is necessary to know the behavior of explosive gases as well as their dispersion method. CFD technique was used to study the dynamics of methane circulation inside the piping of a ventilation installation with the help of the ANSYS MULTIPHISICS software package. The paper presents the CFD analysis regarding the influence of the state parameters on the methane flow dynamics inside the ventilation systems. Thus, the state parameters determined in the experimentation area and their introduction into CFD modeling are presented, namely the establishment of the methane flow and dispersion model in ventilation ducts with high complexity.

INSTABILITY IN POISEUILLE FLOW IN A BIDISPERSE POROUS MEDIUM WITH RELATIVELY LARGE MACROPORES

The hydrodynamic stability of an incompressible fluid flowing through a bidisperse porous medium is being investigated. The problem has been investigated when the Darcy theory is applied to micropores and the Brinkman theory is applied to macropores. This includes an incompressible fluid at isothermal conditions confined in an infinite channel with a constant pressure gradient throughout its length. The fluid moves laminarly along the pressure gradient, generating a parabolic velocity profile that is independent of time. Flow in a circular duct is shown to be stable to small disturbances for all Reynolds numbers, whereas flow in a plane-parallel channel is unstable if the Reynolds number exceeds a critical value, which depends on the problem parameters.

Kidney macrophages tap the stream

Tissue-resident macrophages are essential for maintaining organismal homeostasis, but the precise mechanisms that macrophages use to perform this function are not fully understood. In this issue of Immunity, He etal. demonstrate that renal macrophages surveil and sample urine particles, ensuring optimal collecting duct flow and preventing kidney stone development.

Optimization of Laminar Flow in Non-Circular Ducts: A Comprehensive CFD Analysis

Optimization of Laminar Flow in Non-Circular Ducts: A Comprehensive CFD Analysis

냉각수 분사에 따른 일차원 열평형 관유동 해석 코드 개발

냉각수 분사에 따른 일차원 열평형 관유동 해석 코드 개발