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A model is proposed for liquid film profile prediction in gas-liquid two-phase flow, which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction. A two-fluid model is used to calculate both gas and liquid phases' flow characteristics. The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced. Moreover, energy conservation is applied for obtaining the liquid film thickness distribution along the circumference. Liquid film thickness distribution is calculated accordingly for different cases; its values are compared with other models and available experimental data. As a result, the newly proposed model is tested and good performances are demonstrated. The liquid film thickness distribution in small pipes and inclined pipes is also studied, and regime transition is revealed by liquid film profile evolution. The observed inflection point demonstrates that the liquid film thickness decreases steeply along the circumference, when the circle angle ranges between 30° and 50° for gas-liquid stratified flow with small superficial velocities. [ABSTRACT FROM AUTHOR]

In this work, a priori analysis of machine learning (ML) strategies is carried out with the goal of data-driven wall modeling for large eddy simulation (LES) of gas turbine film cooling flows. High-fidelity flow datasets are extracted from wall-resolved LES (WRLES) of flow over a flat plate interacting with the coolant flow supplied by a single row of 7-7-7 shaped cooling holes inclined at 30 degrees with the flat plate at different blowing ratios (BR). The WRLES are performed using the high-order Nek5000 spectral element computational fluid dynamics (CFD) solver. Light gradient boosting machine (LightGBM) is employed as the ML algorithm for the data-driven wall model. Parametric tests are conducted to systematically assess the influence of a wide range of input flow features (velocity components, velocity gradients, pressure gradients, and fluid properties) on the accuracy of ML wall model with respect to prediction of wall shear stress. In addition, the use of spatial stencil and time delay is also explored within the ML wall modeling framework. It is shown that features associated with gradients of the streamwise and spanwise velocity components have a major impact on the prediction fidelity of wall model, while the effect of gradients of wall-normal velocity component is found to be negligible. Moreover, adding flow feature information from an x-y-z spatial stencil significantly improves the ML model accuracy and generalizability compared to just using local flow features from the matching location. Overall, highest prediction accuracy is achieved when both spatial stencil and time delay features are incorporated within the data-driven wall modeling paradigm. [ABSTRACT FROM AUTHOR]

With future global warming projections, how lightning activity changes in the warmer world is still a debated and challenging question. During the Indian pre‐monsoon season (March–May), land surface heating and moisture availability due to prevailing winds from the neighbouring oceans provide favourable conditions for thunderstorm formation. Based on 24 years of lightning data from 2000 to 2023 detected by Lightning Imaging Sensor/Optical Transient Detector (LIS/OTD) and Indian Lightning Location Network (ILLN), the trend of lightning flashes over western India (15°–22°N, 72.5°–81°E) has been investigated. Our results demonstrate a steady decline in lightning activity during the pre‐monsoon season over western India, which contradicts the previous studies suggesting an increasing lightning trend over the Indian Subcontinent and other parts of the world. Our analysis has shown a falling trend of lightning activity at a rate of −0.066 flashes·km−2 year−1 from 2000 to 2013 (LIS/OTD) and −0.14 M flashes·year−1 from 2014 to 2023 (ILLN). Our observation and previous research strongly suggested that the pressure difference between the land and the neighbouring oceans during pre‐monsoon and monsoon has been weakening for a long time over the Indian region, and we have found a consistent reduction in wind speed over the study region. Here, we propose that the enhanced Indian Ocean warming potentially weakens the land–sea thermal contrast and, thereby, reduces the horizontal pressure gradient. Further, the decreasing trend in the land–sea horizontal pressure gradient resulted in a declining rate of wind speed over western India, affecting moisture transport over land. Thus, the study emphasizes the impact of the decreased land–sea horizontal pressure gradient on declining lighting activity in western India. [ABSTRACT FROM AUTHOR]

Globally, enhanced oil recovery (EOR) has become a pressing issue as the demand for crude oil continues to increase. This study investigates the flow and thermal-fluid–solid coupling of crude oil in a rod pump during hot water recovery and obtains the maximum recovery of crude oil in a vertical pipeline through numerical analysis. The pressure gradient in the pump barrel was first developed and deduced based on the ideal gas state equation and Bernoulli's equation. According to the rheological experiment results, it was proven that the light crude oil conforms to the Newtonian constitutive equation. Subsequently, the momentum equation of crude oil flowing in the pipeline and fluid–solid coupling heat transfer equations were established and solved using the finite difference method. The effects of the thermal recovery temperature Tw, wall thickness c, and stroke time n of the rod pump on flow Q are discussed. In particular, the flow Q within 1 min first increases and then slows down with the increase in stroke time n and reaches its maximum value at n = 7 r/min. Furthermore, flow Q decreases with an increase in c but increases as Tw increases; c = 1.2 cm, Tw = 363 K is the best oil recovery scheme. [ABSTRACT FROM AUTHOR]

The investigation of the couple stress fluid flow behaviour between two parallel plates under sudden stoppage of the pressure gradient is considered. Initially, a flow of couple stress fluid is developed between the two parallel plates under a constant pressure gradient. Suddenly, the applied pressure gradient is stopped, and the resulting unsteady flow is studied. This type of flow is known as run-up flow in the literature. Now the flow is expected to come to rest in a long time. Usually, these types of problems are solved by using the Laplace transform technique. There are difficulties in obtaining the inverse Laplace transform; hence, many researchers adopt numerical inversions of Laplace transforms. In this paper, the problem is solved by using the separation of variables method. This method is easier than the transform method. The velocity field is analytically obtained by applying the usual no-slip condition and hyper-stick conditions on the plates, and hence the volumetric flow rate is derived at subsequent times. The steady state solution before the withdrawal of the pressure gradient is matched with the initial condition on time. The rest time, i.e. the time taken by the fluid to come to rest after the pressure gradient is withdrawn is calculated. The graphs for the velocity field at different times and different couple stress parameters are drawn. In the special case when a couple stress parameter approaches infinity, couple stress fluid becomes a viscous fluid. Our results are in good agreement with this special case. [ABSTRACT FROM AUTHOR]

In endovascular therapy (EVT) for femoropopliteal artery (FPA) lesions, studies examining the relationship between lesion morphology and hemodynamic status are limited. The purpose of this study was to investigate FPA lesion characteristics, including imaging findings and their cutoff values that can predict hemodynamic significance after balloon angioplasty. This single-center retrospective study enrolled 50 de novo FPA lesions from 43 patients treated under intravascular ultrasound (IVUS) usage between June 2022 and March 2023. As a physiological parameter, the pressure gradient was measured, and the cutoff value of the residual pressure gradient (RPG) was defined as a systolic pressure > 10 mmHg through the lesions after balloon angioplasty. The pressure gradients were measured using a 0.014-inch wire-guided, rapid exchange-type microcatheter, Navvus II (Acist, Eden Prairie, Minnesota, USA). Predictive risk factors for RPG were analyzed using the random forest (RF) method. The relationship between the variables, RPG, and the cutoff points of each predictor was assessed using the partial dependence plot (PDP) method. RPG was observed in 20% of the lesions after balloon angioplasty. The RF model revealed that the percent diameter stenosis (%DS) and minimum lumen area (MLA) on IVUS assessment were strong predictive factors for RPG after balloon angioplasty. The PDP model revealed that a higher %DS (cutoff 30%) and smaller MLA (cutoff 10 mm2) could predict RPG after balloon angioplasty. Conventional lesion parameters such as %DS and MLA can predict hemodynamic significance during EVT for FPA lesions. [ABSTRACT FROM AUTHOR]

This study investigates pressure gradient dynamics within a porous medium in the context of two-phase fluid flow, specifically water and sand particle interactions. Using experimental data, we refine pressure correction coefficients within a numerical solution framework, employing the Semi-Implicit Method for the Pressure-linked Equations algorithm. Our findings highlight the relative nature of pressure gradient phenomena, with particle size and volume fraction emerging as crucial determinants. Graphical representations reveal a clear trend: an increase in volume fraction, up to 40%, across varying Reynolds Numbers, leads to a transition towards non-Newtonian behavior in the two-phase fluid system. Unlike the linear pressure gradient seen in single-phase fluid flow, the interplay between liquid and solid phases, along with drag forces, imparts a distinctly nonlinear trajectory to the pressure gradient in two-phase fluid flow scenarios. As the two-phase flow enters a porous medium, numerous factors come into play, resulting in a pressure drop. These factors include changes in cross-sectional geometry, alterations in boundary layer dynamics, and ensuing momentum fluctuations. Interestingly, an increase in porosity percentage inversely correlates with pressure gradient, resulting in reduced pressure gradient with higher porosity levels. [ABSTRACT FROM AUTHOR]

Mavacamten is a first-in-class, targeted, cardiac-specific myosin inhibitor approved by the US Food and Drug Administration for the treatment of adults with symptomatic New York Heart Association Classes II and III obstructive hypertrophic cardiomyopathy (oHCM). Mavacamten was developed to target the hyper-contractile phenotype, which plays a critical role in the pathophysiology of the disease. In Phase 2 and 3 clinical trials, mavacamten was well tolerated, reduced left ventricular outflow tract gradients, improved exercise capacity and symptoms, and was associated with improvements in other clinically relevant parameters, such as patient-reported outcomes and circulating biomarkers. In addition, treatment with mavacamten was associated with evidence of favourable cardiac remodelling in multi-modality imaging studies. Mavacamten substantially reduced guideline eligibility for septal reduction therapy candidates with oHCM and drug-refractory symptoms. In this article, the available efficacy and safety data from completed and ongoing clinical studies of mavacamten in patients with symptomatic oHCM are reviewed. Longer term extension studies may help address questions related to the positioning of mavacamten in current oHCM management algorithms, interactions with background therapy, as well as the potential for disease modification beyond symptomatic relief of left ventricular outflow tract obstruction.

Abstract Background In bypass surgery for moyamoya disease (MMD), the superficial temporal artery’s (STA) pressure needs to surpass that of the cortical M4 recipient of the middle cerebral artery (MCA), boosting cerebral blood flow into the MCA and enhancing cerebral circulation. This study investigates the STA-MCA arterial pressure parameters and gradients during bypass surgery, aiming to deepen our understanding of hemodynamic shifts pre- and post-operation. Methods DSA imaging data were prospectively collected from patients diagnosed with bilateral MMD who underwent STA-MCA bypass surgery between 2022 and 2023 and stratified according to the Suzuki stage. The mean arterial pressure (MAP) of the donor and recipient arteries was directly measured during the STA-MCA bypass procedure, and these data were statistically analyzed and evaluated. Results Among 48 MMD patients, Suzuki grading revealed that 43.8% were in early stages (II and III), while 56.2% were in advanced stages (IV, V, and VI). Predominantly, 77.1% presented with ischemic-type MMD and 22.9% with hemorrhagic type. Pre-bypass assessments showed that 62.5% exhibited antegrade blood flow direction, and 37.5% had retrograde. The mean recipient artery pressure was 35.0 ± 2.3 mmHg, with a mean donor-recipient pressure gradient (δP) of 46.4 ± 2.5 mmHg between donor and recipient arteries. Post-bypass, mean recipient artery pressure increased to 73.3 ± 1.6 mmHg. No significant correlation (r = 0.18, P = 0.21) was noted between δP and Suzuki staging. Conclusion Our study elucidated that cerebral blood pressure significantly decreases beyond the moyamoya network at the distal M4 segment. Furthermore, we observed bidirectional flow in MCA territories and a significant positive pressure gradient between the STA and M4 segments. The lack of correlation between Suzuki stages and M4 pressures indicates that angiographic severity may not reflect hemodynamic conditions before surgery, highlighting the need for customized surgical approaches.

This study investigates pressure gradient dynamics within a porous medium in the context of two-phase fluid flow, specifically water and sand particle interactions. Using experimental data, we refine pressure correction coefficients within a numerical solution framework, employing the Semi-Implicit Method for the Pressure-linked Equations algorithm. Our findings highlight the relative nature of pressure gradient phenomena, with particle size and volume fraction emerging as crucial determinants. Graphical representations reveal a clear trend: an increase in volume fraction, up to 40%, across varying Reynolds Numbers, leads to a transition towards non-Newtonian behavior in the two-phase fluid system. Unlike the linear pressure gradient seen in single-phase fluid flow, the interplay between liquid and solid phases, along with drag forces, imparts a distinctly nonlinear trajectory to the pressure gradient in two-phase fluid flow scenarios. As the two-phase flow enters a porous medium, numerous factors come into play, resulting in a pressure drop. These factors include changes in cross-sectional geometry, alterations in boundary layer dynamics, and ensuing momentum fluctuations. Interestingly, an increase in porosity percentage inversely correlates with pressure gradient, resulting in reduced pressure gradient with higher porosity levels.

Plantar pressure, a common gait and foot biomechanics measurement, is typically analyzed using proprietary commercial software packages. Regional plantar pressure analysis is often reported in terms of underlying bony geometry, and recent advances in image processing and accessibility have made computed tomography, radiographs, magnetic resonance imaging, or other imaging methods more popular for incorporating bone analyses in biomechanics. Can a computed tomography-based regional mask provide comparable regional analysis to commercial plantar pressure software and can the increased flexibility of an in-house method obtain additional insight from common measurements? A plantar pressure analysis method was developed based on bony geometry from computed tomography scans to calculate peak pressure, pressure time integral incorporating sub-peak values, force time integral, pressure gradient, and pressure gradient angle. Static and dynamic plantar pressure were acquired for 4 subjects (male, 65 ± 2.4 years). Plantar pressure variables were calculated using commercial and computed tomography-based systems. Dynamic peak pressure, pressure time integral, and force-time integral computed using the bone-based software was 5 % (9kPa), 7 % (0.3kPa-s) and 13 % (0.3 N-s) different than the commercial software on average. Region masks of the metatarsals and toes differed between commercial and computed tomography-based software due to subject-specific bone geometry and toe shape. Pressure time integral values incorporating sub-peak pressure were higher and demonstrated higher relative hindfoot values compared to those without. Removing step-on frames to static pressure analysis decreased forefoot pressures. Regional maps of peak pressure and maximum pressure gradient demonstrate different peak locations. Computed tomography-based regional masks are comparable to commercial masks. Inclusion of static step-on frames and sub-peak pressures may change regional plantar pressure patterns. Differences in location of maximum pressure gradient and peak pressure may be useful for assessing subject specific injury risk. • Plantar pressure masks can be automatically generated from computed tomography • Locations of peak pressure gradients and peak pressures may be different • Including sub-peak pressures in pressure-time integral may change regional trends [ABSTRACT FROM AUTHOR]

This paper presents the results of extensive testing of four recently proposed algebraic laminar-turbulent transition (LTT) models, which are significantly more computationally effective than differential models, while being potentially equally accurate. The models chosen for evaluation, namely, SST KD, SST kγ, SST alg-γ, and SA BCM, are implemented in the in-house code NTS and verified by comparing the obtained results with those published by the models' authors. The experimental database used for the evaluation of the models includes transitional boundary layers at different free-flow turbulence intensities with and without the pressure gradient, four airfoil flows with different LTT scenarios, and a tandem of two airfoils. It is found that at low levels of turbulence, the results of the SA BCM and SST kγ models may depend on the initial approximation, which does not allow them to be recommended for engineering applications. The best results, comparable in accuracy to those of differential models, are obtained using the SST alg-γ model. [ABSTRACT FROM AUTHOR]

Fluid production from unconsolidated reservoirs often leads in sand production, which poses a number of issues. Sand deposition in flowlines can result in significant pressure dips, pipe and facility damage, and obstructions that decrease productivity. More research is needed to understand the movement and deposition of sand in oil--water--sand (O--W--S) fluxes. This article focuses on O--W--S flows in a 6-meter-long horizontal pipe with an inner diameter of 0.0381 m. The study looks at the flow behavior of high viscosity oil-water (O--W), wateresand (W--S), and oil--water--sand (O--W--S) flows. Experiments were carried out at 250 psig pressure in a laboratory flow test facility using various heavy synthetic oils (viscosities ranging from 3500 cP to 7500 cP at 25°C) and tap water. The sand concentration varied from 1% to 10%, with an average sand particle diameter of 145 mm and material density of 2630 kg/m³. Water cuts ranged from 0.0 to 1.0. The experimental results revealed a minor change in pressure gradient between (O--W) and (O--W--S) flows. However, increasing the sand concentration in (O--W--S) flow resulted in higher pressure losses. The reduction factor of pressure gradient indicated that the highest decrease in pressure drop occurred at higher superficial oil velocities. Furthermore, a direct relationship was observed between the reduction factor and the decrease in water cut. The results also showed that the minimum required transportation velocity for sand slurry decreased with increasing superficial oil velocity, while the minimum transportation condition increased with higher sand concentration. The comparison between the expected pressure gradient from Bannwart and McKibben et al. and the actual experimental data demonstrated significant accuracy for the oil viscosities and superficial oil velocities used in the study. [ABSTRACT FROM AUTHOR]

This work presents an experimental study on oil–water flow downstream of a restriction. The flow pattern, volumetric phase distribution, and their impacts on pressure drop are discussed. We employed two techniques to visualize the oil–water flow patterns, a high-speed camera and an Electrical Capacitance Volume Tomography (ECVT) system. The ECVT system is a non-intrusive device that measures the volumetric phase distribution at the pipe cross-section with time, which plays a critical role in determining the continuous phase in the oil–water flow, and therefore the oil–water flow pattern. In this study, we delved into the oil–water flow pattern and volumetric phase distribution for different valve openings, flow rates, and water cuts, and how they impact the pressure drop. The experimental results have demonstrated a strong relationship between the oil–water flow pattern and the pressure gradient, while the oil–water flow pattern is significantly influenced by the flowing conditions and the valve openings. The impacts of water cuts on the oil–water flow pattern are more obvious for smaller valve openings. For large valve openings, the oil and water phases tend to be more separated. This results in a moderate variation in the pressure gradient as a function of water cuts. However, it becomes more complex as the valve opening decreases. The pressure gradient generally increases with decreasing valve openings until the flow pattern becomes an oil-in-water dispersed flow. The impact of the valve on the pressure gradient is more pronounced in water-dominated flow when the water cut is above the inversion point, while it seems to be most obvious for medium water cut conditions. [ABSTRACT FROM AUTHOR]

Transporting viscous oils through pipelines is usually challenging due to their very high viscosity. Significant friction reduction in the transportation of viscous oils through pipelines using an ecologically friendly way is the most appealing feature of the core annular Flow (CAF) technique. An experimental study has been conducted to investigate the flow patterns and pressure gradient of viscous oil-water two-phase flow in a horizontal acrylic pipe with a 50 mm inner diameter. The test section was equipped with a fluid lubrication injector element to artificially provide CAF. The pressure gradient measurements were focused on the CAF pattern. The prediction models of the CAF pressure gradient were reviewed and evaluated. An empirical prediction model of CAF pressure gradient was developed, relying on both the present and previously published experimental results. The flow patterns were classified into five patterns. It was observed that the CAF occupied a large region in the constructed flow pattern map and its frictional pressure gradient closely resembles that of water flowing alone. It was found that the developed empirical model provided quite good predictions of the experimental pressure gradients and significantly outperformed the original model. The reviewed prediction models in this area for CAF either overpredicted or underpredicted the experimental pressure gradients. Some of these models considered the extensive effect of viscous oil adhered to the inner wall of the pipe, while others neglected the effect entirely. [ABSTRACT FROM AUTHOR]

Background: In bypass surgery for moyamoya disease (MMD), the superficial temporal artery's (STA) pressure needs to surpass that of the cortical M4 recipient of the middle cerebral artery (MCA), boosting cerebral blood flow into the MCA and enhancing cerebral circulation. This study investigates the STA-MCA arterial pressure parameters and gradients during bypass surgery, aiming to deepen our understanding of hemodynamic shifts pre- and post-operation. Methods: DSA imaging data were prospectively collected from patients diagnosed with bilateral MMD who underwent STA-MCA bypass surgery between 2022 and 2023 and stratified according to the Suzuki stage. The mean arterial pressure (MAP) of the donor and recipient arteries was directly measured during the STA-MCA bypass procedure, and these data were statistically analyzed and evaluated. Results: Among 48 MMD patients, Suzuki grading revealed that 43.8% were in early stages (II and III), while 56.2% were in advanced stages (IV, V, and VI). Predominantly, 77.1% presented with ischemic-type MMD and 22.9% with hemorrhagic type. Pre-bypass assessments showed that 62.5% exhibited antegrade blood flow direction, and 37.5% had retrograde. The mean recipient artery pressure was 35.0 ± 2.3 mmHg, with a mean donor-recipient pressure gradient (δP) of 46.4 ± 2.5 mmHg between donor and recipient arteries. Post-bypass, mean recipient artery pressure increased to 73.3 ± 1.6 mmHg. No significant correlation (r = 0.18, P = 0.21) was noted between δP and Suzuki staging. Conclusion: Our study elucidated that cerebral blood pressure significantly decreases beyond the moyamoya network at the distal M4 segment. Furthermore, we observed bidirectional flow in MCA territories and a significant positive pressure gradient between the STA and M4 segments. The lack of correlation between Suzuki stages and M4 pressures indicates that angiographic severity may not reflect hemodynamic conditions before surgery, highlighting the need for customized surgical approaches. [ABSTRACT FROM AUTHOR]

In this article, we analyses electroosmosis augmented MHD peristaltic transport of SWCNTs suspension in porous media, the basic equations have been constructed under assumptions of low Reynolds number and long wave length. The exact solution by the regular perturbation technique are obtained and the flow qualities have been plotting by using MATHEMATICA software for all the figures. Series solution for stream function, pressure gradient and temperature distribution have been computed in the peristaltic transport in an asymmetric channel. [ABSTRACT FROM AUTHOR]

Based on High Magnetic field Helicon eXperiment, considering the parabolic distribution and Gaussian distribution of radial plasma density, HELIC code was used to study the influence of temperature and pressure gradient on power deposition, electric field, and current density of Helicon Wave Plasma. Three different gradients (positive, negative, and zero gradient) were selected. The results show that positive temperature gradient is beneficial to increase the relative absorption power at the center of plasma. Compared with negative and zero pressure gradients, positive pressure gradient increases the relative absorption power and weakens the current density at the center of plasma, and increases the electric field intensity at the edge of plasma. Larger edge heating will cause the relative absorption power at edge to rise rapidly, which is not conducive to the coupling at the center of plasma. In practical experiments, it is particularly important to reduce the heating effect at edge by cooling the antenna itself. Three different gradients of temperature and pressure have little effect on electric field intensity and current density in plasma, and the variation trend is basically similar, which proves the stability of the antenna mode: m = 1. [ABSTRACT FROM AUTHOR]

Purpose: In arterial disease, the presence of two or more serial stenotic lesions is common. For mild lesions, it is difficult to predict whether their combined effect is hemodynamically significant. This study assessed the hemodynamic significance of idealized serial stenotic lesions by simulating their hemodynamic interaction in a computational flow model. Materials and Methods: Flow was simulated with SimVascular software in 34 serial lesions, using moderate (15 mL/s) and high (30 mL/s) flow rates. Combinations of one concentric and two eccentric lesions, all 50% area reduction, were designed with variations in interstenotic distance and in relative direction of eccentricity. Fluid and fluid–structure simulations were performed to quantify the combined pressure gradient. Results: At a moderate flow rate, the combined pressure gradient of two lesions ranged from 3.8 to 7.7 mmHg, which increased to a range of 12.5–24.3 mmHg for a high flow rate. Eccentricity caused an up to two-fold increase in pressure gradient relative to concentric lesions. At a high flow rate, the combined pressure gradient for serial eccentric lesions often exceeded the sum of the individual lesions. The relative direction of eccentricity altered the pressure gradient by 15–25%. The impact of flow pulsatility and wall deformability was minor. Conclusion: This flow simulation study revealed that lesion eccentricity is an adverse factor in the hemodynamic significance of isolated stenotic lesions and in serial stenotic lesions. Two 50% lesions that are individually non-significant can combine more often than thought to hemodynamic significance in hyperemic conditions. [ABSTRACT FROM AUTHOR]

Identification of the decomposition law of the binder in composites provides the basis for a mathematical model and analysis of the thermal state of most composites in significantly nonsteady high-temperature loading. The decomposition law of the binder permits analysis of the thermal state of composites without considering the chemical kinetics. Verification of the numerical results confirms the validity of this approach to modeling the thermal state of composites for use in hypersonic aircraft. [ABSTRACT FROM AUTHOR]

At medium to high gas content rates, the gas-liquid separation phenomenon and the stagnation behaviors of the gas masses occurring in the impeller channels are essential factors affecting the hydraulic performance of multiphase pumps. This paper designs a split trailing edge flap suitable for the multiphase pump to improve the hydraulic performance in the impeller by varying the flap deflection angle and length. The model's reliability was assessed by comparing the experimental outcome with the external characteristics of the experimental data. Based on the Eulerian-Eulerian multiphase model and the SST k‐ω turbulence model, the effects of different flap lengths on external characteristics, the turbulent kinetic energy and pressure distribution are analyzed. The study results show that when the length of the separated trailing edge flap is 0.25 l 0 and the deflection angle is 5°, the transporting efficiency of the multiphase pump is the highest at IGVF=50% with an efficiency increase of 3.40% compared to the original model. Its optimal flap length scheme effectively reduces the radial pressure gradient and the inverse pressure gradient in the impeller channel, which suppresses the gas blockage phenomenon to a certain extent. [ABSTRACT FROM AUTHOR]

The study focuses on the flow patterns and pressure drop characteristics of three crude oils and water in a horizontal pipe. The experimental results showed that the transformation boundary of the flow pattern and phase inversion water fraction were related to the flow parameters. Comparing the three oils, it was found that the viscosity and composition of the oil also significantly influence the flow performance, which can be explained by the adsorption properties of the asphaltenes at the oil-water interface. In particular, the droplet size in water-in-oil dispersion flow was observed and measured. It showed that the water droplet size decreased with the increase of oil viscosity, the decrease of water content, the drop of temperature, and the growth of mixing velocity, probably due to higher shear stress and lower frequency of collision and coalescence between droplets. The apparent viscosity of water-in-oil emulsions was calculated by the rheological model, and the qualitative relation between flow parameters and interfacial area concentration on apparent viscosity was obtained. Taking the influence of interfacial area concentration into consideration, a simple and accurate viscosity model was established based on dimensional analysis, which is of great significance for process design in gathering and transportation systems. [ABSTRACT FROM AUTHOR]

In order to investigate the atmospheric mechanisms governing the occurrence of the Von phenomenon at the time of forest fires in northern Iran, four types of data were used in the research, changes in parameters such as temfaature, pressure and wind were investigated. Networked data from the National Environmental Prediction / Atmospheric Science Centers (NCEP / NCAR) and the European Center for Medium-Term Atmospheric Prediction (ECMWF) were then used to explain the structure of the atmosphere. Modis sensor images were used to study the surface temfaature of the earth and suspended airborne particle model was used to track air masses. It was found that during the study faiod, the event of January 25-31, 2007 is one of the strongest and most favasive phones that occur in the region. The results showed that by forming a high pressure cell located in the south of the country and a low pressure cell in the wind protection part of Alborz mountain, it has created a strong pressure gradient and has caused the south current to affect the northern regions of Iran. Accordingly, during a static-dynamic process, a wind turbine rotational current has been formed in the Alborz mountain range wind turbine, with the ascent of the air mass on the Alborz mountain range and also its moisture discharge and the passage of the air package over the mountain and its flow in the region and the heatless heat, the hot and dry air mass enters the region which is accompanied by strong winds Has been affected by fire-prone areas. With an increase in wind speed and a positive temfaature drop there is a sudden jump and increase in temfaature tracking also showed that the main source of current entering the region is in the northern part of the Persian Gulf and northeastern Africa. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paste slurry exhibits pipe wall slip characteristics during transportation, thereby effectively reducing pipeline transportation resistance. In order to study the characteristics of paste pipeline transportation with wall slip characteristics, a pipeline pressure gradient model considering wall slip effect was applied. In order to verify the accuracy of the model, the overflow tailings and classified tailings of a lead-zinc mine were taken as the research object. According to the two-dimensional compaction theory, the mixing ratio of overflow tailings was determined to be 8% ∼ 39%, and five kinds of tailings with different gradations were configured accordingly. The loop test, rheological test and settlement test were carried out. Taking the rheological parameters, limit volume concentration and average particle size as the basic parameters, the pressure gradient value considering the wall slip effect is obtained and compared with the measured pressure gradient of the loop test. The results show that the relative error between the model prediction results and the measured values is 10%, which has high reliability. The pressure gradient and mass concentration show a quadratic function growth trend, and have a linear relationship with the pipeline flow rate. With the increase of the proportion of －38 µm particles, the pressure gradient shows a secondary growth trend. With the increase of the proportion of + 38 µm particles, the pressure gradient shows a quadratic function decreasing trend; The slip drag reduction rate gradually decreases with the increase of mass concentration, and is not affected by the flow rate of the pipeline. When the proportion of －38 µm particle size is 27.43% ∼ 38.32%, the slip reduction rate is more significant. Considering the actual project and transportation cost, the corresponding overflow tailings incorporation ratio is 16% ∼ 31%.

Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants, typically by creating active air infiltration through the difference between supply and exhaust air volumes. The door gap is the channel of air flow between rooms, so its height has an important influence on the pressure difference and infiltration air volume of the room. There is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the building. In this study, model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM, and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases department. The results show that in a building with ventilation system divided by functional area, the difference in the height of the door gaps requires different active infiltration air volumes. Pressure fluctuations in the medical and patient corridors are greater than in other rooms. The significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 patients. It is also instructive for the design of pressure gradients in clean workshops, biological laboratories, and other similar buildings.

Featured Application: This study aims to fill a knowledge gap in rarefied gas flows, addressing the complexities related to wall temperatures and pressure differentials in the simulation of gas–solid interactions in nanoscale and microscale geometries. The findings are relevant to diverse microfluidic applications, encompassing devices such as micro–nano electronic devices. Simulations were carried out in non-dimensional form so that the results can be extended to all noble gases. As computer capabilities improve, Molecular Dynamics simulations are becoming more important for solving various flow problems. In this study, Couette and Poiseuille flows at different wall temperatures were investigated using a hard-sphere Molecular Dynamics simulation approach. Although a low spacing ratio was used in the simulations, the results are valid for rarefied gas flows when proper scaling based on the Knudsen number was used because only binary collisions with a hard-sphere model were considered. The main focus of this study was the examination of the effects of various wall speeds, pressure gradients, and wall temperatures. A pressure gradient was generated by developing a modified selective periodicity condition in the flow direction. With the combined effect of the pressure gradient and the wall velocities, subsonic, transonic, and supersonic speeds in nanochannels were examined. With the combination of different parameters, 1260 simulation cases were conducted. The results showed that there are temperature and velocity slips that are dependent on not only the temperature and velocity values but also on the magnitudes of a pressure gradient. The pressure gradient also caused nonlinearities in temperature and velocity profiles. [ABSTRACT FROM AUTHOR]

The utilization of numerical methods, such as computational fluid dynamics (CFD), has been widely established for modeling patient-specific hemodynamics based on medical imaging data. Hemodynamics assessment plays a crucial role in treatment decisions for the coarctation of the aorta (CoA), a congenital heart disease, with the pressure drop (PD) being a crucial biomarker for CoA treatment decisions. However, implementing CFD methods in the clinical environment remains challenging due to their computational cost and the requirement for expert knowledge. This study proposes a deep learning approach to mitigate the computational need and produce fast results. Building upon a previous proof-ofconcept study, we compared the effects of two different artificial neural network (ANN) architectures trained on data with different dimensionalities, both capable of predicting hemodynamic parameters in CoA patients: a one-dimensional bidirectional recurrent neural network (1D BRNN) and a three-dimensional convolutional neural network (3D CNN). The performance was evaluated by median point-wise root mean square error (RMSE) for pressures along the centerline in 18 test cases, which were not included in a training cohort. We found that the 3D CNN (median RMSE of 3.23 mmHg) outperforms the 1D BRNN (median RMSE of 4.25 mmHg). In contrast, the 1D BRNN is more precise in PD prediction, with a lower standard deviation of the error (±7.03 mmHg) compared to the 3D CNN (±8.91 mmHg). The differences between both ANNs are not statistically significant, suggesting that compressing the 3D aorta hemodynamics into a 1D centerline representation does not result in the loss of valuable information when training ANN models. Additionally, we evaluated the utility of the synthetic geometries of the aortas with CoA generated by using a statistical shape model (SSM), as well as the impact of aortic arch geometry (gothic arch shape) on the model's training. The results show that incorporating a synthetic cohort obtained through the SSM of the clinical cohort does not significantly increase the model's accuracy, indicating that the synthetic cohort generation might be oversimplified. Furthermore, our study reveals that selecting training cases based on aortic arch shape (gothic versus non-gothic) does not improve ANN performance for test cases sharing the same shape. [ABSTRACT FROM AUTHOR]

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Blowout is among catastrophic accidents in oil and gas drilling, and it is caused by abnormal pressure resulted from gas kick from reservoir which cannot be prevented due to limits of drilling technology. Accurate prediction of wellbore pressure is an effective method to prevent blowout. Based on electrical capacitance volume tomography (ECVT), the experiments of gas and white oil two-phase flow with viscosity of 16 mPa·s, 23 mPa·s, 26 mPa·s and 39 mPa·s in vertical annulus are carried, and the pressure drop in vertical annulus is tested. Considering the influence of viscosity, modification of the friction loss coefficient and prediction of the pressure gradient in bubble flow, slug flow and churn flow are studied. The prediction accuracy of the modified model is compared with the pressure gradient model established in the Caetano’s experiment (air-kerosene, ID 42.2 mm and OD 76.2 mm). The results show that under the Caetano’s experimental conditions and the experimental conditions of this experiment, the maximum error and the prediction mean absolute error of the pressure gradient model with the corrected friction loss coefficient are lower than those of Caetano’s model. [ABSTRACT FROM AUTHOR]

The problem of micro-pressure waves caused by the high-speed train passing through the tunnel from the open line become more and more serious with the increase of the train speed. The combined buffer structure can better mitigate the impact of micropressure waves than the single type of buffer structure. In order to further alleviate the impact of micro-pressure waves on the surrounding environment of the tunnel, a buffer structure named ladder ventilation type combined buffer structure was proposed. Based on the standard κ-ε two-equation turbulence model ( κ is the turbulent kinetic energy, ε is dissipation rate) and the numerical simulation method, four ventilation window parameters were studied, including the ventilation distance, the ventilation ratio, the number of ventilation windows, and the position of ventilation windows. The initial compression wave pressure and pressure gradient caused by the train entering the tunnel with different ventilation windows were analyzed, and the optimum parameters of the combined buffer structure were obtained. The buffer structure has less impact on the maximum pressure of the initial compression wave, but more impact on the initial compression wave pressure gradient. When the ventilation distance is 4 m, the ventilation rate α is 36%, the number of ventilation windows is 2, and the position of ventilation windows is the top ventilation, it is the optimal working condition, and the mitigation effect on pressure gradient reaches 60.14%. [ABSTRACT FROM AUTHOR]

Valvular heart conditions significantly contribute to the occurrence of cardiovascular disease, affecting around 2–3 million people in the United States. The anatomical characteristics of cardiac muscles and valves can significantly influence blood flow patterns inside the ventricles. Understanding the interaction between the mitral valve and left ventricle structures enables using fluid–structure interaction simulations as a precise and user-friendly approach to investigating outcomes that cannot be captured using experimental approaches. This study aims to develop a 3D-0D computational model to simulate the consequences of extending the anterior mitral leaflet towards the left ventricle in the presence of the thickness of the left ventricular septum and the mitral valve device. The simulations presented in this paper successfully showcased the ability of the model to replicate occlusion occurring at the left ventricular outflow tract and illustrated the impact of this blockage on the flow pattern and pressure gradient. Furthermore, these simulations conducted following anterior mitral leaflet splitting can emphasize the significance of this technique in reducing the obstruction at the left ventricle outflow tract. The computational model presented in this study, combining 3D and 0D elements, provides significant insights into the flow patterns occurring in the left ventricle before and after anterior leaflet splitting. Thus, expanding this model can help explore other cardiac phenomena and investigate potential post-procedural complications. [ABSTRACT FROM AUTHOR]

This study focuses on optimization of pressure gradient on MHD peristaltic nanofluid flow by response surface methodology (RSM). The governing equations, including continuity, motion, nanoparticle, and concentration force are solved by disregarding inertial forces and employing the approximation of long-wavelength. The perturbation method is used to solve the resultant nonlinear coupled partial differential equation analytically. Mathematical and graphical outputs for concentration, temperature, and pressure rise, considering all physical parameters, are presented. Numerical computation is applied to assess expressions for friction forces and pressure rise. Magnetohydrodynamics has various applications in various microchannel designs for efficacious flow control in pumping fluids for both pulsating and non-pulsating continuous flow. Finally, Response Surface Methodology (RSM) is used for performing sensitivity analysis and its optimization. ANOVA tables are generated with the help of MINITAB-19 which is a statistical software. The sensitivity results are displayed in tabular and graphical form and concluded that M is more sensitive than other input parameters for ΔPat the low level and the input parameter Nt is most sensitive among others at middle and high levels. Further, Temperature and pressure of the flow has different responses for various values of magnetic, thermophoresis and Brownian motion parameter.

Kidney stones, known medically as nephrolithiasis, present a significant health concern globally, particularly in regions such as India and the Middle East. Despite extensive research, the complexity of ureteral obstruction due to kidney stones remains a challenge in urology. This study addresses this gap by analysing the effects of obstruction in a three-dimensional model of the ureter with a constant diameter, simulating various percentages of blockage. Through computational analysis, the pressure and velocity effects on the ureter wall are explored, providing insights into the dynamics of obstructed ureters. Building upon previous research, this study contributes to a deeper understanding of the factors influencing flow patterns and pressure variations within the urinary tract. Additionally, findings from this study may lead to advancements in non-invasive assessment methods for diagnosing and treating ureteral obstruction caused by kidney stones. Furthermore, insights gained from this research could potentially inform clinical decision-making, leading to improved management strategies and better outcomes for patients affected by this debilitating condition. The novelty of this work lies in its comprehensive analysis of the effects of obstruction on the ureteral wall, offering valuable implications for urological practice and patient care.

When high-speed trains enter tunnels, an initial compression wave is generated. As the compression wave propagates at the local speed of sound to the tunnel exit, it radiates into the surrounding environment, forming micro-pressure waves (MPWs). MPWs create sonic booms, resulting in significant environmental issues. The magnitude of the micro-pressure waves is directly proportional to the pressure gradient of the compression wave at the tunnel exit. The nonlinear effects of the initial compression wave during propagation lead to a significant increase in pressure gradient. Therefore, the propagation characteristics of the initial compression wave during the tunnel are the crucial factor affecting the amplitude of MPWs. Based on the one-dimensional compressible unsteady non-isentropic flow model and the improved generalized Riemann variable characteristic method, this paper researched the propagation and evolution characteristics of an initial compression wave generated when 400 km/h high-speed trains enter tunnels with three portal shapes: (no tunnel entrance hood (no hood), an oblique, enlarged tunnel entrance hood (type A), an enlarged equal-section non-uniform opening hole tunnel entrance hood (type B)). The results show that when the initial compression wave propagates inside very long tunnels, the pressure gradient of the compression wave exhibits a trend of initially increasing and then decreasing with the increase in propagation distance. When the pressure gradient of the compression wave reaches its maximum value, the corresponding propagation distance is the steepening critical distance. For no tunnel entrance hoods, type A tunnel entrance hoods, and type B tunnel entrance hoods, the steepening critical distances are 5 km, 6 km, and 16 km, respectively. The steepening critical distance shortens with increasing train speed. Steady friction and unsteady friction effects mainly affect the pressure amplitude and pressure gradient during compression wave propagation, respectively. At lower ambient temperatures, the nonlinear effects in compression wave propagation are significantly enhanced. The mitigation effects of type A tunnel entrance hoods and type B tunnel entrance hoods on pressure gradient reduction are mainly concentrated within 4 km and 12 km, respectively. It is necessary to determine the optimal matching relationship between the tunnel entrance hood and tunnel length based on the characteristics of compression wave propagation to ensure their mitigating performance is maximized.

Background: The direct quantitative measurement of donor and recipient pressures in patients with moyamoya vasculopathy (MMV) during superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery has yet to be reported in academic literature. Method: Using a wireless pressure wire, we describe our approach to measuring seven pressure parameters in MMV patients step-by-step. Conclusion: Direct intraluminal pressure measurement of donor and recipient arteries provides a practical and accurate means to quantify cerebral hemodynamic parameters in MMV patients, enhancing understanding of individualized hemodynamic changes pre- and post-surgery. [ABSTRACT FROM AUTHOR]

It is of great significance to propose corresponding development strategies based on the formation mechanism and utilization limits of remaining oil, in order to improve the development effect during the high water cut period. Firstly, the distribution pattern of remaining oil in different pore throat radii under high magnification displacement was analyzed using a combination of core displacement experiments and T2 spectroscopy. Then, a micro parallel model of large and small pore throats was established, and the Bernoulli flow equation was applied to reveal the retention mechanism of crude oil in small pore throats and the critical displacement pressure gradient. Finally, the large and small pore throats were transformed into high and low permeability layers at the reservoir scale, considering the starting pressure gradient, and the iterative method was used to determine the technical boundaries for producing residual oil. The results indicate that as the displacement ratio increases, the radius is greater than 50 μm The crude oil in the m large pore throat is continuously expelled, and the water phase gradually becomes a continuous phase, with a significant interference radius of 10 ~ 50 μm. The crude oil in the small pore throat flows, resulting in the formation of a “water injection bypass flow” to retain remaining oil. At this point, the average radius of the small pore throat is 35 μm. The corresponding critical displacement pressure gradient is 0. 06 MPa / m. Determine the technical boundary for effective utilization of remaining oil. As the displacement pressure gradient increases, the rate of increase in displacement efficiency first accelerates and then slows down. During the high water cut period of Bohai SZ Oilfield, a horizontal well combined directional well layered development model was adopted. The displacement pressure gradient increased by 1. 8 times, the oil recovery rate increased by 0. 8 percentage points, and the water drive recovery rate increased by 16. 8 percentage points, greatly improving the development effect and further developing and enriching the efficient development theory of continental heavy oil fields. [ABSTRACT FROM AUTHOR]

This paper aims to propose correlations to predict pressure gradient, friction factor and fluid phase hold-up in liquid-liquid horizontal pipe flow. To develop the correlations, experiments are conducted using high viscous oils (202 and 630 mPa⋅s) in a steel pipe of length 11.25 m and length-to-diameter ratio of 708. In addition, the experimental data from the literature comprising wide range of flow and fluid properties is analyzed. For the analysis, the liquid-liquid pipe flow data is categorized into two as: stratified and dispersed. The existing friction factor correlations are modified to incorporate the effects of viscosity of the oil phase, interfacial curvature (contact/wetting angle-in lieu of material of the pipe) and fluid phase fraction. In the two-fluid model of stratified flow, the wall stress and interfacial stress correlations are substituted with superficial velocities of fluids and superficial Reynolds numbers of fluid phases replacing fluid phase velocities and fluid Reynolds numbers. Similarly, for dispersed flow, an effective Reynolds number is described as the sum of superficial Reynolds number of oil and water phases. Substituting the generally employed mean or mixture Reynolds number with the effective Reynolds number into the existing single-phase turbulent flow friction factor correlation, an effective friction factor for oil-water flow is proposed. Employing the proposed correlations, the pressure gradient across the oil-water flow and hold-up volume fraction are predicted with significant reduction in error compared with that of conventionally employed correlations. The average error and standard deviation values of −7.06%, 20.72% and 0.31%, 18.79% are found for stratified flow and dispersed flow respectively. [ABSTRACT FROM AUTHOR]

A technique for modeling turbulent flow in a channel with impermeable and permeable walls in the presence of heat supply to the wall is proposed. To close the equations of the boundary layer, a three-parameter differential model of shear turbulence is used, which is supplemented by a transfer equation for a turbulent heat flux. Calculations are carried out for a developed turbulent flow in a round pipe with impermeable and permeable walls for air and binary gas mixtures with a low molecular Prandtl number with parameters corresponding to those in earlier experiments. The results of studies on the effect of the Prandtl number on heat transfer in a pipe with impermeable walls for a coolant with constant physical properties are consistent with the experimental data and empirical dependences of W.M. Kays and B.S. Petukhov for the Nusselt number in the range of Prandtl numbers of 0.2–0.7. It is shown that a positive pressure gradient arising in a pipe under strong gas suction leads to a violation of the similarity of the velocity and temperature profiles and, as a consequence, to a violation of the Reynolds analogy. The use of the transport equation for a turbulent heat flux makes it possible to take into account the complex dependence of the turbulent Prandtl number on the molecular Prandtl number in the viscous sublayer and in the logarithmic boundary layer. The influence of the variability of thermophysical properties and the turbulent Prandtl number on the characteristics of heat transfer in a pipe is estimated. Thus, the difference between the Nu number determined under the assumption of a constant turbulent Prandtl number and the results obtained in calculations using the equation for turbulent heat flux increases with a decrease in the molecular Prandtl number and an increase in the intensity of gas suction. [ABSTRACT FROM AUTHOR]

Erosive beach scarps influence beach vulnerability, yet their formation remains challenging to predict. In this study, a 1:2.5 scale laboratory experiment was used to study the subsurface hydrodynamics of a beach dune during an erosive event. Pressure and moisture sensors buried within the dune were used both to monitor the water table and to examine vertical pressure gradients in the upper 0.3 m of sand as the slope of the upper beach developed into a scarp. Concurrently, a line‐scan lidar tracked swash bores and monitored erosion and accretion patterns along a single cross‐shore transect throughout the experiment. As wave conditions intensified, a discontinuity in the slope of the dune formed; the discontinuity grew steeper and progressed landward at the same rate as the R2% runup extent until it was a fully formed scarp with a vertical face. Within the upper 0.15 m of the partially saturated sand, upward pore pressure gradients were detected during backwash, influencing the effective weight of sand and potentially contributing to beachface erosion. The magnitude and frequency of the upward pressure gradients increased with deeper swash depths and with frequency of wave interaction, and decreased with depth into the sand. A simple conceptual model for scarp formation is proposed that incorporates observations of upward‐directed pressure gradients from this study while providing a reference for future studies seeking to integrate additional swash zone sediment transport processes that may impact scarp development. Plain Language Summary: Dunes are important protective features of many sandy coasts around the world. Often, when dune erosion occurs, steep faces known as scarps form. Scarps can erode landward quickly, and it is therefore useful to understand when and where they might form. Here, a large‐scale laboratory experiment was used to study the processes involved in the erosion of a dune. The water pressure and moisture content within the dune sediments, and the runup extent and changing elevation of the sand were observed simultaneously. During the experiment, a scarp developed as the wave heights, periods, and water levels increased. As waves passed over the sand surface, the water pressure within the sand changed rapidly, sometimes causing differences (gradients) in pressure between sand at different depths. If the pressure gradients became high enough and were directed upwards, they put an upward force on the sand grains, potentially making them prone to erosion. Upward‐directed pressure gradients were observed as wave conditions grew more energetic. To show how the processes observed in this study may have contributed to the formation of the scarp in the experiment, a conceptual model of scarp formation is proposed. Key Points: A 1:2.5 scale laboratory experiment was used to study the subsurface hydrodynamics of a beach dune during an erosive eventDestabilizing pressure gradients were identified within the sand surface, and were impacted by swash conditions and depth within the sandA conceptual model for scarp formation is proposed that incorporates observations from this study and could guide future work [ABSTRACT FROM AUTHOR]

Purpose: To estimate relative transvalvular pressure gradient (TVPG) noninvasively from 4D flow MRI. Methods: A novel deep learning–based approach is proposed to estimate pressure gradient across stenosis from four‐dimensional flow MRI (4D flow MRI) velocities. A deep neural network 4D flow Velocity‐to‐Presure Network (4Dflow‐VP‐Net) was trained to learn the spatiotemporal relationship between velocities and pressure in stenotic vessels. Training data were simulated by computational fluid dynamics (CFD) for different pulsatile flow conditions under an aortic flow waveform. The network was tested to predict pressure from CFD‐simulated velocity data, in vitro 4D flow MRI data, and in vivo 4D flow MRI data of patients with both moderate and severe aortic stenosis. TVPG derived from 4Dflow‐VP‐Net was compared to catheter‐based pressure measurements for available flow rates, in vitro and Doppler echocardiography–based pressure measurement, in vivo. Results: Relative pressures calculated by 4Dflow‐VP‐Net and in vitro pressure catheterization revealed strong correlation (r2 = 0.91). Correlations analysis of TVPG from reference CFD and 4Dflow‐VP‐Net for 450 simulated flow conditions showed strong correlation (r2 = 0.99). TVPG from in vitro MRI had a correlation coefficient of r2 = 0.98 with reference CFD. 4Dflow‐VP‐Net, applied to 4D flow MRI in 16 patients, showed comparable TVPG measurement with Doppler echocardiography (r2 = 0.85). Bland–Altman analysis of TVPG measurements showed mean bias and limits of agreement of −0.20 ± 2.07 mmHg and 0.19 ± 0.45 mmHg for CFD‐simulated velocities and in vitro 4D flow velocities. In patients, overestimation of Doppler echocardiography relative to TVPG from 4Dflow‐VP‐Net (10.99 ± 6.77 mmHg) was observed. Conclusion: The proposed approach can predict relative pressure in both in vitro and in vivo 4D flow MRI of aortic stenotic patients with high fidelity. [ABSTRACT FROM AUTHOR]

A new law is proposed for the nonlinear filtration of pyrolytic gases generated when heat-shielding composite binders decompose during the aerodynamic heating of high-speed aircraft. The nonlinearity arises when the inertial terms in the equations of gas flow and heat transfer through the porous coke residue are taken into account. These equations are written for considerable pressure gradients of the pyrolytic gases, in contrast to the small gradients described by Darcy's linear law. In deriving the new law, a function of the filtrational Reynolds number is introduced. That function is expanded in series, with the retention of linear terms. The resulting law may be used in analyzing filtration in the porous coke residue of heat-shielding composite binders and also in the heat transfer equation taking account of nonlinear and nonisothermal filtration. [ABSTRACT FROM AUTHOR]

In developing and transporting significant oil fields in deep-sea environments, multiphase pumps are considered crucial energy conversion equipment. Ensuring their safe, efficient, and stable operation is currently a primary focus of research. The intermittent aggregation of the gas phase at the trailing edge flap of the impeller blades in multiphase pumps can lead to periodic and significant fluctuations in flow rate and outlet pressure, posing a threat to the overall operational safety of the pump system. Based on aerodynamic principles, this paper presents the design of a separate trailing edge flap for the impeller blades. The inner nodal method is applied to determine the design scheme of the trailing edge flap for the multiphase pump. A numerical approach is employed to analyze the impact of the flap deflection angle on the internal flow characteristics to provide theoretical guidance for the structural optimization of multiphase pumps. The results indicate that the influence of the deflection angle on the pump efficiency is complex and affected by a critical angle value. When the deflection angle is below the critical value, the trailing edge flap can effectively reduce the formation of energy dissipation vortices and radial pressure gradients within the impeller channel, enabling a significant improvement in the gas-phase aggregation phenomenon caused by gas–liquid separation. However, additional energy losses occur at the connection between the trailing edge flap and the main blade body for deflection angles exceeding the critical value. When the trailing edge flap length is 0.25 l and the deflection angle is 5°, the efficiency is improved by 3.4% compared to the original model. Consequently, the pressurization capacity of the pump is compromised. In the design and application of trailing edge flaps, a careful balance between various factors is required to ensure both the stability and high efficiency of the pump system. [ABSTRACT FROM AUTHOR]