Change In Pressure Gradient Research Articles

Numerical investigation on dimpled target average heat transfer in free-surface water jet impingement and its enhancement effect versus flat plate target

Jet impingement serves as an effective method to enhance heat transfer in diverse industrial applications, utilizing either a separate fluid from the ambient (free-surface jet) or identical fluids (submerged jet). The target surface undergoes distinct thermal processes, featuring zones like the stagnation zone, boundary layer formation, and the transition from laminar to turbulent wall flow. However, heat transfer efficiency diminishes significantly due to pressure gradient changes beyond the stagnation zone, impeding flow and boundary layer development. Addressing this decline through surface modification techniques, such as incorporating spherical dimples, emerges as an innovative approach. This study develops a numerical model via Computational Fluid Dynamics (CFD) simulations utilizing Volume of Fluid (VOF) modeling for water jet impingement on a flat plate target. The model’s validity is established by comparing hydrodynamic and thermal aspects in both laminar and turbulent scenarios against established experimental data in literature. Nine dimpled target surfaces, featuring diverse dimensional properties and positioning configurations, are examined using this model to explore potential enhancements in heat transfer intensity. The findings indicate a notable increase in the overall surface average Nusselt number, potentially reaching up to 50% by implementing dimples in the current context. Moreover, the study highlights that the radial distribution of dimples and the non-uniform flow path ahead of the incoming fluid, which differs from parallel flat flow, result in varying effects based on dimensional properties. For instance, it has been found that modifying dimensions such as deepening dimples or altering their proximity could yield contrary effects, emphasizing the need for an optimization methodology to determine the most efficient dimpled surface setup within a given geometry.

Long-term clinical outcomes after alcohol septal ablation for hypertrophic obstructive cardiomyopathy in Japan: a retrospective study.

Hypertrophic cardiomyopathy is characterized by significant left ventricular wall thickening, often leading to obstructive symptoms. Alcohol septal ablation (ASA) has emerged as an effective treatment for patients with hypertrophic obstructive cardiomyopathy (HOCM) who remain symptomatic despite maximal medical therapy. However, the detailed long-term effects of ASA in Japanese patients with HOCM remain unclear. Therefore, this study aimed to investigate the long-term effects of ASA for HOCM by evaluating changes in symptoms, pressure gradient, hemodynamics, prognosis, and predictive factors for cardiovascular events over time. In this retrospective study, we examined 239 highly symptomatic patients (age, 64 ± 13years; median follow-up, 6.9years) treated with ASA for drug-refractory HOCM between 1998 and 2021. Patients were assessed using transthoracic echocardiography, magnetic resonance imaging, and cardiac catheterization. Follow-up evaluations included clinical assessments, electrocardiography, and echocardiography. Data analysis included descriptive statistics, Kaplan-Meier analysis, and multivariate regression. ASA reduced the left ventricular outflow tract gradient from 90.5 ± 52.8 to 14.4 ± 17.1mmHg (P < 0.01) and New York Heart Association (NYHA) class from 3 [2.5-3] to 1 [1-2] at 10years after ASA (P < 0.01). The 30-day mortality rate following ASA was 1%. Overall, 31 patients (13%) died during the follow-up period. The survival rates at 1, 5, 10, and 15years after ASA were 97.4%, 89.9%, 83.7%, and 77.6%, respectively. Multivariable analysis revealed NYHA functional class before ASA (odds ratio [OR], 3.09; 95% confidence interval [CI], 1.40-6.82; P = 0.005), beta-blocker use (OR, 0.25; 95% CI, 0.07-0.91; P = 0.036), and class Ia agent use (OR, 0.31; 95% CI, 0.13-0.75; P = 0.009) as independent predictors of all-cause mortality. This study demonstrated low periprocedural and long-term mortality rates following ASA in patients with HOCM, suggesting that ASA provides durable symptomatic relief and reduces left ventricular outflow tract obstruction in selected highly symptomatic patients with HOCM.

Drug treatments to prevent first decompensation in cirrhosis.

Cirrhosis is a prevalent condition affecting more than 100 million people globally and carrying significant morbidity and mortality related to the development of portal hypertension and hepatic decompensation. Current treatment is primarily targeted at identifying chronic liver disease early and preventing the progression of fibrosis by treating the underlying etiology of liver disease. Treatment options for patients with advanced fibrosis are limited, and the only drug class approved for the prevention of hepatic decompensation remains non-selective beta blockers. There are several pharmacological therapies being developed in both preclinical and clinical trials to explore their efficacy in preventing first hepatic decompensation. Most studies evaluate primary endpoints reflective of disease severity and portal hypertension, such as change in hepatic venous pressure gradient or fibrosis stage based on histology or imaging. While many drugs are being investigated, much work is still needed to identify treatment targets with effective outcomes in order to move the needle in the field of cirrhosis management. This narrative review will address the current state of cirrhosis therapies including potential new therapeutic targets as well as provide direction on future advancements that will improve our current treatment paradigm and lead to better outcomes for those burdened with cirrhosis.

Combination of carvedilol with variceal band ligation in prevention of first variceal bleed in Child-Turcotte-Pugh B and C cirrhosis with high-risk oesophageal varices: the ‘CAVARLY TRIAL’

ObjectivesBeta-blockers and endoscopic variceal band ligation (VBL) have been preferred therapies for primary prophylaxis of variceal bleeding. However, the choice of therapy in patients with advanced liver disease with high-risk...

Atrial refractoriness early after transcatheter aortic valve implantation TAVI in patients with severe aortic stenosis and sinus rhythm.

Aortic valve stenosis (AS) is a common valvular heart disease, especially in the elderly, and is associated with a high prevalence of atrial fibrillation. Although the risk of atrial fibrillation is expected to decrease after the intervention, atrial fibrillation develops in many patients undergoing surgical or percutaneous transaortic valve implantation. We aimed to evaluate atrial refractoriness since it may play a key role in the occurrence of atrial fibrillation after transaortic valve implantation. Seventy-nine consecutive patients who underwent TAVI between October 2021 and May 2023 were enrolled in this trial. Sixty-seven patients underwent electrophysiology study before and after TAVI. We evaluated the changes in PA and AH intervals, as well as atrial effective refractory periods. Besides the hemodynamic changes, atrial effective refractory periods increased, and atrial effective refractory period dispersion (39.8±21.6 vs. 31.1±18.0) decreased significantly after TAVI. The change in atrial effective refractory period dispersion after TAVI was correlated only with the changes in left ventricular end-diastolic pressure (r=0.77, P=0.001) and the changes in aortic gradient (r=0.4, P=0.001). The independent variables affecting the changes in atrial effective refractory period dispersion were basal pro-BNP levels, besides the changes in left ventricular end-diastolic pressure and aortic gradient after transaortic valve implantation. Our results show an acute improvement in atrial refractoriness after TAVI, though high atrial fibrillation rates are reported in the literature. The timing of aortic valve replacement is important, as irreversible maladaptive changes might have already developed by the time of intervention.

Revisiting historical trends in the Eastern Boundary Upwelling Systems with a machine learning method

Eastern boundary upwelling systems (EBUS) host very productive marine ecosystems that provide services to many surrounding countries. The impact of global warming on their functioning is debated due to limited long-term observations, climate model uncertainties, and significant natural variability. This study utilizes the usefulness of a machine learning technique to document long-term variability in upwelling systems from 1993 to 2019, focusing on high-frequency synoptic upwelling events. Because the latter are modulated by the general atmospheric and oceanic circulation, it is hypothesized that changes in their statistics can reflect fluctuations and provide insights into the long-term variability of EBUS. A two-step approach using Self-Organizing Maps (SOM) and Hierarchical Agglomerative Clustering (HAC) algorithms was employed. These algorithms were applied to sets of upwelling events to characterize signatures in sea-level pressure, meridional wind, shortwave radiation, sea-surface temperature (SST), and Ekman pumping based on dominant spatial patterns. Results indicated that the dominant spatial pattern, accounting for 56%-75% of total variance, representing the seasonal pattern, due to the marked seasonality in along-shore wind activity. Findings showed that, except for the Canary-Iberian region, upwelling events have become longer in spring and more intense in summer. Southern Hemisphere systems (Humboldt and Benguela) had a higher occurrence of upwelling events in summer (up to 0.022 Events/km²) compared to spring (&amp;lt;0.016 Events/km²), contrasting with Northern Hemisphere systems (&amp;lt;0.012 Events/km²). Furthermore, long-term changes in dominant spatial patterns were examined by dividing the time period in approximately two equally periods, to compare past changes (1993-2006) with relatively new changes (2007-2019), revealing shifts in key variables. These included poleward shifts in subtropical high-pressure systems (SHPS), increased upwelling-favorable winds, and SST drops towards higher latitudes. The Humboldt Current System (HumCS) exhibited a distinctive spring-to-summer pattern, with mid-latitude meridional wind weakening and concurrent SST decreases. Finally, a comparison of upwelling centers within EBUS, focusing on changes in pressure and temperature gradients, meridional wind, mixed-layer depth, zonal Ekman transport, and Ekman pumping, found no evidence supporting Bakun’s hypothesis. Temporal changes in these metrics varied within and across EBUS, suggesting differential impacts and responses in different locations.

Haemodynamic significance of extrinsic outflow graft stenoses during HeartMate 3™ therapy.

The HeartMate 3 (HM3) implantable left ventricular assist device connects the left ventricle apex to the aorta via an outflow graft. Extrinsic obstruction of the graft (eOGO) is associated with serious morbidity and mortality and recently led to a Food and Drug Administration Class 1 device recall of HM3. This study aimed to provide a better understanding of the haemodynamic impact of extrinsic stenoses. Computed tomography (CT) images of two retrospectively identified patients with eOGO (29 and 36% decrease in cross-sectional area, respectively, by radiological evaluation) were acquired with a novel photon-counting CT system. Numerical evaluations of haemodynamics were conducted using a high-fidelity 3D computational fluid dynamics approach on both the patient-specific graft geometries and in two virtually augmented stenotic severities and three device flows. Visual analysis identified increased velocity, pressure, and turbulent flow in the outer anterior curvature of the outflow graft; however, changes in graft pressure gradients were slight (1-9 mmHg) across the range of stenosis severities and flow rates tested. Evidence of eOGO during HM3 support and the recent device recall can provoke clinical apprehension and interventions. The haemodynamic impact of a stenosis detected visually or by quantification of cross-sectional area reduction may be difficult to predict and easily overestimated. This numerical study suggests that, for clinically encountered flow rates and stenosis severities below 61% in cross-sectional area decrease, eOGO may have low haemodynamic impact. This suggests that patients without symptoms or signs consistent with haemodynamically significant obstruction might be managed expectantly.

Hartmann Flow of Two-Layered Fluids in Horizontal and Inclined Channels

The effect of a transverse magnetic field on two-phase stratified flow in horizontal and inclined channels is studied. The lower heavier phase is assumed to be an electrical conductor (e.g., liquid metal), while the upper lighter phase is fully dielectric (e.g., gas). The flow is defined by prescribed flow rates in each phase, so the unknown frictional pressure gradient and location of the interface separating the phases (holdup) are found as part of the whole solution. It is shown that the solution of such a two-phase Hartmann flow is determined by four dimensionless parameters: the phases’ viscosity and flow-rate ratios, the inclination parameter, and the Hartmann number. The changes in velocity profiles, holdups, and pressure gradients with variations in the magnetic field and the phases’ flow-rate ratio are reported. The potential lubrication effect of the gas layer and pumping power reduction are found to be limited to low magnetic field strength. The effect of the magnetic field strength on the possibility of obtaining countercurrent flow and multiple flow states in concurrent upward and downward flows, and the associated flow characteristics, such as velocity profiles, back-flow phenomena, and pressure gradient, are explored. It is shown that increasing the magnetic field strength reduces the flow-rate range for which multiple solutions are obtained in concurrent flows and the flow-rate range where countercurrent flow is feasible.

Evaluation and clinical significance of contrast-enhanced ultrasound on changes in liver blood flow perfusion after TIPS surgery.

To investigate the clinical value of contrast-enhanced ultrasound in the prediction of hepatic encephalopathy (HE) in patients with hepatitis B cirrhosis after intrahepatic portal-systemic shunt via jugular vein. In this retrospective study, we collected data from 75 patients with hepatitis B, cirrhosis, and portal hypertension who underwent jugular intrahepatic portosystemic shunt from February 2019 to February 2022. The diagnostic instrument used was the TOSHIBA Aplio500 color Doppler ultrasound with contrast-enhanced ultrasound capabilities. The trial group comprised 20 patients with HE within 3 months postsurgery, while the control group (CG) included 55 patients without HE within the same postoperative period. All patients underwent various examinations before and within 48 hours after surgery, including observation of liver and spleen size and stent position, as well as assessment of blood flow direction in portal and hepatic veins. Subsequently, contrast-enhanced ultrasound was employed to examine and observe perfusion changes of contrast agents in hepatic veins, hepatic arteries, and portal veins (PV). Changes in PV pressure gradient, intrahepatic, and stent blood flow perfusion (BFP) were explored in both postoperative trials and CGs. The trial group exhibited higher BFP volume, PV pressure gradient difference, and percentage decrease compared to the CG. A weak positive correlation was observed between blood flow within the liver stent and PV pressure gradient difference, as well as the percentage decrease in PV pressure gradient. The correlation coefficient between blood flowing perfusion volume within the stent and the difference in PV pressure gradient was R = 0.415 (P = .000). The correlating coefficient between BFP amount within the stent and the percentage decrease in PV pressure gradient was R = 0.261 (P = .027). The area under the receiver operating characteristic curve for stent perfusion volume, difference in PV pressure gradient, and percentage decrease in PV pressure gradient was 0.691, 0.759, and 0.742, respectively. An increase in PV pressure gradient accelerates blood flow within the stent, predisposing to HE. Changes in hepatic BFP following transjugular intrahepatic portosystemic shunt can effectively predict the occurrence of HE, demonstrating significant clinical relevance.

Research of technological processing of semi-finished products in the manufacture of profile products from composite materials

This article examines the process of technological processing of semi-finished product in the manufacture of rod profile products from fibrous composite materials, in particular - round. The purpose is to determine the theoretical value of the parameter which ensures the necessary impregnation of the winding layer during the final moulding of profile products. It is mentioned that in order to ensure a defined structure and degree of filling during the production of rod profile products from spirally reinforced semi-finished products, they are compacted. Compaction can take place in one of two methods: by pressing in a spinneret, crimping with winding. The second method is used in the production of round cross-section rods. In this case, the spirally reinforced structural elements, which initially have a circular cross-sectional shape, deform and acquire an elliptical shape. At the same time, the degree of reinforcement filling of the central part of the structural element changes. The volume of binder removed during deformation per unit time is presented as a function of the ellipse parameter.The displacement of the binder at steady-state mode of moulding is considered.Law of change of pressure gradient along the length of formed element before molding front is defined. The volume of binder removed during bundle formation per unit time is determined. Required molding pressure necessary to ensure a given degree of filling has been determined. It is shown that it is possible to calculate the parameters of a deformed element that will ensure that the binder fills the space between the elements. An equation for determining the value of the parameter of the degree of crimping of an element, depending on the diameter of the used semi-finished product and the thickness of the winding layer is obtained. Data on critical values of a parameter of a degree of crimping of element, depending on diameter of a half-finished product and thickness of a layer of a winding is resulted. A method of determining the parameter of the degree of crimping of the element, which ensures the necessary impregnation of the winding layer during the forming of the profiled products, is proposed.

An Experimental Study on the Seepage Characteristics of Rough Fractures in Coal under Stress Loading

Fracture and stress environments significantly affect the flow of coalbed methane. Under stress, fracture deformation and damage occur, which change the original fracture characteristics and lead to changes in gas flow characteristics. The change in gas pressure gradient makes the fluid flow obviously nonlinear. Using linear flow theory to describe the fracture flow leads to a large error in predicting coalbed methane productivity. In this study, seepage tests on fractured coal are carried out under different stresses and gas pressure gradients, the nonlinear flow and changes in related parameters are analyzed, and the applicability of the nonlinear flow equation is evaluated. The resulting seepage of the gas flow in the fracture under stress is obviously nonlinear, which gradually increases with increasing effective stress and gas pressure gradient. When the Forchheimer equation is used to characterize the nonlinear seepage in fractures, the coefficients increase with increasing effective stress. The permeability, nonlinear factor, and critical Reynolds number decrease with increasing effective stress. When the Izbash equation is used for this case, the linear coefficient ranges from 1015 to 1016, and the nonlinear coefficient ranges from 1.064 to 1.795. The coefficients are related to the effective stress through a power function. Both the Forchheimer and Izbash equations can characterize the flow in rough fractures in coal during stress loading. However, the Forchheimer equation better reveals the mechanism of flow transformation from linear to nonlinear in fractures.

Experimental investigation of flow patterns and rheological characteristics of compressed air foam in horizontal tube

The use of compressed air foam (CAF) for fire suppression has undergone rapid development in recent years. It has been successfully applied in fire incidents in the petroleum and chemical industries. The increasing need to fighting fires at high elevations necessitates an understanding of the rheological characteristics, pressure gradient changes, flow characteristics, and regularities of CAF within long firehoses. Therefore, this paper focuses on an investigation of the flow characteristics of CAF at foaming agent concentrations ranging from 0.1% to 1.2% and gas–liquid ratios ranging from 5 to 25. Specifically, it explores foam characteristics, pressure loss, and the relationship between flow rate and foaming agent concentration. The findings reveal that CAF exhibits four flow patterns: wave flow, elastic flow, ring flow, and dispersion flow. For most CAF firefighting applications, a foaming agent concentration of 0.3%–0.5% and a gas–liquid ratio of approximately 10 are suitable. However, for fire isolation purposes, a foaming agent concentration of 0.7%–1.0% and a gas–liquid ratio of over 15 should be employed. By utilizing a power-law rheological model and an experimental regression method, a prediction model is obtained for the flow characteristics and pressure loss of CAF in pipelines. The predictions of the model exhibit an error of less than 10% when compared with experimental results, validating the model. The results of this study provide a theoretical basis and technical support for understanding liquid supply resistance loss, which is crucial for maximizing firefighting effectiveness.

Effect of Displacement Pressure Gradient on Oil–Water Relative Permeability: Experiment, Correction Method, and Numerical Simulation

Relative permeability is a fundamental parameter affecting reservoir development performance analysis. During the development of oil and gas fields, the displacement pressure gradient changes with time and space. This paper studies the effect of displacement pressure gradient on relative permeability. The oil–water relative permeability curves of a Bohai Oilfield under different displacement pressure gradients are obtained through experimental analysis. Based on the experimental data, a correction model of the permeability curve is established by regression of the Willhite model parameters. The correction model is introduced into the black oil numerical simulation, and the production performance and remaining oil are compared and analyzed. The results show that the displacement pressure gradient can have an obvious impact on the relative permeability curve. As the displacement pressure gradient increases, the two-phase span of the relative permeability curve increases, the oil displacement efficiency increases, and the water relative permeability increases. The relative permeability curves under different displacement pressure gradients can be accurately characterized by the Willhite model. The consideration of the displacement pressure gradient has an obvious impact on numerical simulation results. The conventional method of using a fixed relative permeability curve cannot truly reflect the production performance and the remaining oil distribution. This paper proposes a set of realization methods including obtaining laws from experiments, utilizing the empirical model to correct, and simulating to characterize reservoir changes.

Changes of cerebrospinal fluid pressure gradient in different body positions under experimental impairment of cerebrospinal fluid pathway: new insight into hydrocephalus development.

It is generally accepted that hydrocephalus is a consequence of the disbalance between cerebrospinal fluid (CSF) secretion and absorption which should in turn lead to CSF pressure gradient development and ventricular enlargement. To test CSF pressure gradient role in hydrocephalus development, we experimentally caused CSF system impairment at two sites in cats. In the first group of animals, we caused Sylvian aqueduct obstruction and recorded CSF pressure changes pre and post obstruction at three measuring sites (lateral ventricle -LV, cortical-CSS and lumbar subarachnoid space -LSS) during 15 min periods and in different body positions over 360 degrees. In the second group of experiments, we caused cervical stenosis by epidural plastic semiring implantation and monitored CSF pressure changes pre and post stenosis implantation at two measuring sites (lateral ventricle and lumbar subarachnoid space) during 15 min periods in different body positions over 360 degrees. Both groups of experimental animals had similar CSF pressures before stenosis or obstruction at all measuring points in the horizontal position. During head-up verticalization, CSF pressures inside the cranium gradually became more subatmospheric with no significant difference between LV and CSS, as they are measured at the same hydrostatic level, while CSF pressure inside LSS became more positive, causing the development of a large hydrostatic gradient between the cranial and the spinal space. With cervical stenosis, CSF pressure inside the cranium is positive during head-up verticalization, while in cats with aqueductal obstruction CSF pressure inside the CSS remains negative, as it was during control period. Concomitantly, CSF pressure inside LV becomes less negative, thus creating a small hydrostatic gradient between LV and CSS. Since CSF pressure and gradient changes occur only by shifting body position from the horizontal plane, our results indicate that cervical stenosis in a head-up vertical position reduces blood perfusion of the whole brain, while aqueductal obstruction impairs only the perfusion of the local periventricular brain tissue. It seems that, for evolutionary important bipedal activity, free craniospinal communication and good spinal space compliance represent crucial biophysical parameters for adequate cerebral blood perfusion and prevention of pathophysiological changes leading to the development of hydrocephalus.

Features of forecasting abnormally high reservoir pressures when drilling wells in the areas of Southwestern Turkmenistan

The article provides information on changes in reservoir pressure gradients in the stratigraphic section of strata with increasing depth in the oil and gas fields of the Baltic and Gogerendag-Ekerem zones. The conditions for the formation of abnormally high reservoir pressures occurring are given, as well as the classification of reservoir pressures by the anomaly coefficient. Reservoir pressure of horizons is predicted based on the results of drilling deep wells. This work is useful and can be used to fulfill the tasks set when drilling new deep wells with abnormally high reservoir pressures for their uncomplicated successful completion of construction. Keywords: miocene; drilling speed; drilling mud; hydrodynamics; well.

FLUID FLOW CONTROL IN POROUS MEDIA WITH CONSIDERATION OF ELECTROKINETIC EFFECTS

The paper presents results of the research on the influence of electrokinetic characteristics of fluids on its flow in porous media. Experimental studies have shown the effect of fluid slippage in the channels of porous media due to the electrically charged boundary "liquid-porous medium". It is shown that the change of flow velocity profile and pressure gradient is caused by the display of electrokinetic effects in the filtration of polar liquids.The investigation has shown that the process of the electrolyte solutions filtration in a porous medium is accompanied by the change in the liquid flow rate and the electro-potential of the flow. The periodic nature of changes in flow characteristics is explained by continuous charge formation and charge interaction in the diffuse layer. Periodic charge accumulation and subsequent charge transfer across the channel cross section depending on the charge sign acquired, as well as compression of the diffuse layer with increasing NaCl electrolyte concentration in aqueous solution may be the cause of fluid flow variations. The observed effects may serve as a tool for controlling fluid flow in water-oil-saturated formations and, in particular, injectivity of injection wells by controlling electrical conductivity of water injected into the formation.

Features of forecasting abnormally high reservoir pressures when drilling wells in areas of south-western Turkmenistan

Introduction: The study is essential because predicting areas with high formation pressures in geophysical research is complex. It requires new technologies to accurately locate them and minimize unforeseen emergencies. The purpose of this study is to analyse and identify the peculiarities of predicting anomalously high formation pressures during well drilling in the territory of south-western Turkmenistan in order to provide more effective and reliable pressure management during drilling and operation. Materials and Methods: Methods such as analysis and prediction were used in this study. Results and Discussion: The paper presents valuable research data highlighting the changes in reservoir pressure gradients in the unique stratigraphic section of reservoirs in the oil and gas fields of the Pribalkan and Gogerendag-Ekerem zones. The analysis of the studies reveals the dynamism with which the properties of reservoir rock change with increasing depth of occurrence. Special attention is paid to the processes associated with the formation of anomalously high formation pressures, which is an important aspect for understanding complex geological processes. Conclusions: The study provides a detailed classification of formation pressures, considering the anomaly coefficient, enhancing our understanding of this phenomenon. Predicting formation pressures for specific horizons relies on analyzing deep well drilling results.

Effect of embankment slope on road traffic noise propagation: numerical investigation and construction of correction formula for difference by slope angle

The propagation characteristics of road traffic noise from an embankment road are investigated through three-dimensional wave-based numerical analysis. Since this is a large-scale problem, we use the fast multipole boundary element method (FMBEM) as a highly efficient wave-based numerical method. We analyze sound fields around embankments with various slope angles and clarify that the sound pressure gradient changes with the slope angle, and in particular, the sound pressure level (SPL) distribution changes significantly near the line where the embankment slope meets the ground surface. When the prediction plane is an orthogonal cross-section to the direction of the lane, the distribution of the difference in A-weighted SPL between the case where the embankment is sloped and the case where it has a right angle is generally similar regardless of the position of the prediction plane. Based on this result, we propose an empirical formula to express the difference between the case with a slope and the case with a right angle. We confirm that the proposed formula provides a certain level of accuracy regardless of the location of the prediction plane when we appropriately determine the coefficients in the formula for each case from the viewpoint of error minimization.

Spatio-temporally resolved dynamical transitions in flow of Pickering emulsions through porous media

Pickering emulsions, when formulated using suitable particles, can exhibit both droplet–droplet and droplet–grain attraction while flowing through porous media. Despite their potential impact on the flow behavior of Pickering emulsions, the underlying mechanisms and dynamics of these attractions are not yet fully understood. To address this, we developed a custom-built micro-sandpack apparatus coupled with confocal microscopy to simultaneously measure the pressure gradient and visualize the flow patterns of emulsions. Our results reveal that the flow of attractive Pickering emulsions displays large-amplitude oscillations in the pressure gradient which cannot be explained using traditional models (e.g. geometric straining, filtration, or continuum). We have identified localized flow patterns characterized by particle attachment and deposition to nearby grains, droplet deposition, jamming of droplets within the throat, and droplet release. These patterns occur cyclically, corresponding to the gradual and rapid changes in the overall pressure gradient. Photonic force microscopy confirmed the strength of droplet–droplet attraction and revealed the underlying cause of this flow dynamics: the formation of chains of nanoparticles that tether droplets together. Our work provides new insights into the mechanism for self-regulated morphological evolution of Pickering emulsion during flow through porous media, resulting from the combined effects of droplet jamming/straining (in line with prior observations of emulsion flow through porous media) and particle deposition (typically observed in the flow of particulate suspensions).

Static pressure redistribution mechanism of non-axisymmetric endwall based on radial equilibrium

Non-axisymmetric endwall contouring has been proved to be an effective flow control technique in turbomachinery. Several different flow control mechanisms and qualitative design strategies have been proposed. The endwall contouring mechanism based on the flow governing equations is significant for exploring the quantitative design strategies of the non-axisymmetric endwall contouring. In this paper, the static pressure redistribution mechanism of endwall contouring was explained based on the radial equilibrium equation. A quantified expression of the static pressure redistribution mechanism was proposed. Compressor cascades were simulated using an experimentally validated numerical method to validate the static pressure redistribution mechanism. A geometric parameter named meridional curvature (Cme) is defined to quantify the concave and convex features of the endwall. Results indicate that the contoured endwall changes the streamline curvature, inducing a centrifugal acceleration. Consequently, the radial pressure gradient is reformed to maintain the radial equilibrium. The convex endwall represented by positive Cme increases the radial pressure gradient, decreasing the endwall static pressure, while the concave endwall represented by negative Cme increases the endwall static pressure. The Cme helps to establish the quantified relation between the change in the endwall radial pressure gradient and the endwall geometry. Besides, there is a great correlation between the distributions of the Cme and the change in the endwall static pressure. It can be concluded that the parameter Cme can be considered as a significant parameter to parameterize the endwall surface and to explore the quantitative design strategies of the non-axisymmetric endwall contouring.