Effect of Capsule Density and Concentration on Pressure Drops of Spherical Capsule Train Conveyed by Water

This experimental investigation concerns the hydraulic transport of a spherical capsule train, whose density is equal to that of water (relative density; s=1), in horizontal pipes. In a system where the carrier fluid is water, pressure drops of two phase flow and capsule velocities were measured at 0.2–1.0 m/s bulk velocities and 5–20% capsule transport concentrations. The results found were compared with the pressure gradient (pressure drops per unit length) ratios ((ΔP/L)m/(ΔP/L)w) measured for less dense capsules. The capsule velocity and the velocity ratio (Vc/Vb) increased with increasing the bulk velocity. As concentration increases, the pressure gradient of the capsule-water mixture increases. For all concentrations, the pressure gradient ratio decreases (getting closer to 1) with increasing bulk velocity. This result is similar to that of capsules with less relative density. However, the pressure gradient ratio of the capsule flow with less density is higher than that of capsules with equal density at constant transport concentrations. The reason for this difference is that the capsules with a density equal to that of water move along the axis of the pipe for a longer time. When capsules with equal density are used, the mass flow rate will remain the same, but energy consumption will decrease.

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Frictional Pressure Drops of Two-Phase R-134A Flow in Horizontal and Vertical U-Type Wavy and Straight Tubes

Fluids Engineering ◽

10.1115/imece2006-13247 ◽

2006 ◽

Author(s):

Ing Youn Chen ◽

Yu-Shi Wu ◽

Yu-Juei Chang ◽

Chi-Chuan Wang

Keyword(s):

Pressure Gradient ◽

Flow Pattern ◽

Straight Tube ◽

Two Phase ◽

Pressure Drops ◽

Flow Pattern Transition ◽

The Difference ◽

R 134A ◽

Gradient Ratio ◽

Phase Pressure

This study presents the measurements of R-134a two-phase frictional pressure gradient subject to vertical and horizontal arrangements of a U-type wavy tube with inner diameter of 5.07 mm and a curvature ratio of 5. The ratio between two-phase pressure gradients of U-bend and straight tube is about 2.5 - 3.5. For the straight tube, the frictional two-phase pressure gradient ratio between the vertical and horizontal arrangements is marginally higher (1.0 - 1.2) for annular flow pattern at x > 0.5, and is 1.0 - 1.4 for the U-bend in the wavy tube. The higher resistance in the vertical arrangement is due to the buoyancy force against the flow inertia. However, for x < 0.5, this ratio is gradually increased due to the difference of flow pattern. The ratio is increased to 1.8 in the straight tube. For the U-bend, the ratio is 2.1 for flow entering the upper tube and is 1.5 for flow entering the lower tube at x = 0.1 and G = 200 kg/m2·s. For the vertical wavy tube, additional effects like the flow pattern transition, liquid flow reversal, and freezing slug may cause additional pressure drops.

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Experimental investigation of the effect of diameter ratio on velocity ratio and pressure gradient for the spherical capsule train flow

European Journal of Mechanics - B/Fluids ◽

10.1016/j.euromechflu.2012.05.004 ◽

2013 ◽

Vol 37 ◽

pp. 42-47 ◽

Cited By ~ 2

Author(s):

Deniz Ulusarslan

Keyword(s):

Experimental Investigation ◽

Pressure Gradient ◽

Velocity Ratio ◽

Diameter Ratio ◽

Spherical Capsule

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Swirling Annular Flow in a Steam Separator

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3078701 ◽

2009 ◽

Vol 131 (3) ◽

Cited By ~ 20

Author(s):

Hironobu Kataoka ◽

Yusuke Shinkai ◽

Shigeo Hosokawa ◽

Akio Tomiyama

Keyword(s):

Pressure Drop ◽

Annular Flow ◽

Nuclear Reactor ◽

Water Pressure ◽

Interfacial Friction ◽

Pressure Drops ◽

Pressure Transducers ◽

Ring Configuration ◽

Film Flows ◽

Steam Separator

Effects of pick-off ring configuration on the separator performance of a downscaled model of a steam separator for a boiling water nuclear reactor are examined using various types of pick-off rings. The experiments are conducted using air and water. Pressure drops in a barrel and a diffuser and diameters and velocities of droplets at the exit of the barrel are measured using differential pressure transducers and particle Doppler anemometry, respectively. The separator performance does not depend on the shape of the pick-off ring but strongly depends on the width of the gap between the pick-off ring and the barrel wall. The pressure drop in the barrel is well evaluated using the interfacial friction factor for unstable film flows. Carry-under can be estimated using a droplet velocity distribution at the exit of the separator.

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Numerical Analysis of the Mud Inflow Model of Fractured Rock Mass Based on Particle Flow

Geofluids ◽

10.1155/2021/5599748 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Yongjian Pan ◽

Huajun Wang ◽

Yanlin Zhao ◽

Qiang Liu ◽

Shilin Luo

Keyword(s):

Rock Mass ◽

Pressure Gradient ◽

Flow Direction ◽

Fractured Rock ◽

Water Pressure ◽

Water Inrush ◽

Quadratic Function ◽

Particle Flow ◽

Fractured Rock Mass ◽

Particle Flows

Water inrush and mud outburst are one of the crucial engineering disasters commonly encountered during the construction of many railways and tunnels in karst areas. In this paper, based on fluid dynamics theory and discrete element method, we established a fractured rock mass mud inflow model using particle flow PFC3D numerical software, simulated the whole process of fractured rock mass mud inflow, and discussed the effect of particle size and flow velocity on the change of pressure gradient. The numerical simulation results show that the movement of particles at the corner of the wall when the water pressure is first applied occurs similar to the vortex phenomenon, with the running time increases, the flow direction of particles changes, the vortex phenomenon disappears, and the flow direction of particles at the corner points to the fracture; in the initial stage, the slope of the particle flows rate curves increases in time, and the quadratic function is used for fitting. After the percolation velocity of particles reaches stability, the slope of the curve remains constant, and the primary function is used for fitting; the particle flow rate and pressure gradient are influenced by a variety of factors, and they approximately satisfy the exponential function of an “S” curve.

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Abstract WP121: An Evaluation of Hemodynamics Across Intracranial Steno-occlusive Lesions by Computational Fluid Dynamics

Stroke ◽

10.1161/str.47.suppl_1.wp121 ◽

2016 ◽

Vol 47 (suppl_1) ◽

Author(s):

Florence SY Fan ◽

Vincent HL Ip ◽

Alexander YL Lau ◽

Anne YY Chan ◽

Lisa WC Au ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Pressure Gradient ◽

Pressure Difference ◽

Pressure Ratio ◽

Velocity Ratio ◽

Strongly Correlated ◽

Hemodynamic Parameters ◽

Moderate Correlation ◽

Anterior Circulation

Introduction: Intracranial atherosclerotic steno-occlusive disease (ICAS) is a major cause of stroke worldwide and portends a high risk of recurrence. Computational fluid dynamics (CFD) is a novel technique developed to solve and analyze the dynamic effects of fluid flow. We aimed to analyse hemodynamics across ICAS using CFD on processed CTA images and explore the correlation between the degree of arterial stenosis and hemodynamic flow status. Methods: We recruited patients with symptomatic ICAS from Acute Stroke Unit, Prince of Wales Hospital. All patients received CTA and DSA as vascular workup. Using CFD analysis of processed CTA images, we first defined the hemodynamic parameters, including pressure difference, pressure ratio, pressure gradient, shear strain rate ratio (SSR), wall shear stress (WSS) ratio and velocity ratio, across the stenosed vessels, and then we correlated the severity of stenosis as defined by DSA, with these parameters. Results: Among the 53 recruited patients (mean age 62.9 years, 69.8% males), 45 (85%) had lesions in the anterior circulation. The severity of stenosis showed a weak-to-moderate correlation with pressure difference (rs=0.392, p=0.004), pressure ratio (rs=-0.429, p=0.001) and pressure gradient (rs=0.419, p=0.002). There was no significant correlation between the severity of stenosis with SSR ratio, WSS ratio and velocity ratio. Among patients with anterior circulation stroke or TIA, the severity of stenosis showed a weak to moderate correlation with pressure difference (rs=0.381, p=0.01), pressure ratio (rs=-0.426, p=0.004) and pressure gradient (rs=0.407, p=0.005). For patients with posterior circulation stroke or TIA, the severity of stenosis was strongly correlated with pressure difference (rs=0.714, p=0.047) and pressure ratio (rs=-0.714, p=0.047); and very strongly correlated with velocity ratio (rs=0.833, p=0.01). Conclusions: The severity of ICAS showed only weak-to-moderate correlation with hemodynamic parameters across the culprit lesion. Thus, risk stratification and treatment based solely on stenotic severity may be inadequate. Our findings may guide further research in estimating stroke risks and selection of high-risk patients who may benefit from adjunctive treatments.

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Experimental investigation of coarse particles-water mixture flow in horizontal and inclined pipes

Journal of Hydrology and Hydromechanics ◽

10.2478/johh-2014-0022 ◽

2014 ◽

Vol 62 (3) ◽

pp. 241-247 ◽

Cited By ~ 30

Author(s):

Pavel Vlasák ◽

Zdeněk Chára ◽

Jan Krupička ◽

Jiří Konfršt

Keyword(s):

Dominant Mode ◽

Solid Particles ◽

Coarse Grained ◽

Water Mixture ◽

Mixture Flow ◽

Horizontal Pipe ◽

Pressure Drops ◽

Steel Pipes ◽

Inner Diameter ◽

Inclined Pipes

Abstract The effect of solid concentration and mixture velocity on the flow behaviour, pressure drops, and concentration distribution of coarse particle-water mixtures in horizontal, vertical, and inclined smooth stainless steel pipes of inner diameter D = 100 mm was experimentally investigated. Graded basalt pebbles were used as solid particles. The study revealed that the coarse-grained particle-water mixtures in the horizontal and inclined pipes were significantly stratified. The solid particles moved principally in a layer close to the pipe invert; however for higher and moderate flow velocities, particle saltation became the dominant mode of particle conveyance. Frictional pressure drops in the horizontal pipe were found to be markedly higher than in the vertical pipe, while the frictional pressure drops in the ascending pipe increased with inclination angle up to about 30°.

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1036 Correlation between noninvasive and invasive evaluation of aortic stenosis severity: practicality and accuracy of the ejection-fraction-peak doppler derived aortic pressure gradient ratio

European Journal of Echocardiography ◽

10.1016/s1525-2167(06)60641-0 ◽

2006 ◽

Vol 7 ◽

pp. S173-S173

Author(s):

F IMPERADORE ◽

G MUSURACA ◽

C CEMIN ◽

C VACCARINI ◽

G VERGARA

Keyword(s):

Aortic Stenosis ◽

Ejection Fraction ◽

Pressure Gradient ◽

Aortic Pressure ◽

Stenosis Severity ◽

Gradient Ratio ◽

Invasive Evaluation

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A Comprehensive Study of Asymmetric Micro-Droplet Splitting in T-Junction

Volume 2: Computational Fluid Dynamics ◽

10.1115/ajkfluids2019-5284 ◽

2019 ◽

Author(s):

Way Lee Cheng ◽

Reza Sadr ◽

Arum Han

Keyword(s):

Pressure Gradient ◽

Cfd Simulation ◽

General Criterion ◽

Flow Conditions ◽

Functional Feature ◽

Splitting Ratio ◽

Junction Geometry ◽

Break Up ◽

Gradient Ratio ◽

Underlying Mechanisms

Abstract Splitting a single droplet into two unequal portions using a microfluidic T-junction has been an important functional feature of many modern lab-on-a-chip devices. A recent study introduced a general criterion for asymmetric droplet break-up in the range of intermediate Capillary numbers. The current work attempts to analyze, in more details, the different underlying mechanisms governing the asymmetric break-up process. In particular, this work focuses on the relationship between the break-up mechanism versus the splitting ratio of the daughter droplets. CFD simulation is used to closely monitor the effect of different fluid properties on the evolution of droplet break-up process. The splitting ratio under different flow conditions is characterized. Four mechanisms for primary droplet break-up are defined as follows: break-up with permanent obstruction, unstable break-up, breakup with tunnels and non-breakup. In particular, the main focus of this study is on the unstable break-up mechanisms where is very likely results to a much-deviated splitting ratio. Typically, yet unexpectedly, the resulting splitting ratio is often larger than the pressure gradient ratio in the T-junction. However, the two ratios are approximately equals to each other under a limited set of flow conditions. It has been observed that the splitting ratio could be more than double the pressure gradient ratio of the T-junction. The break-up is observed to be in the permanent obstruction mode if the splitting ratio is about the same magnitude as the pressure gradient ratio. The effects of the T-junction geometry on the break-up will also be examined.

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