Particle Dispersion Simulation in Turbulent Flow Due to Particle-Particle and Particle-Wall Collisions

2015 ◽  
Vol 32 (2) ◽  
pp. 237-244 ◽  
Author(s):  
J.-H. Lin ◽  
K.-C. Chang
Keyword(s):  
Cost Effective ◽  
Small Mass ◽  
Particle Dispersion ◽  
Hard Sphere Model ◽  
Wall Roughness ◽  
Mass Loading ◽  
Particle Collisions ◽  
Carrier Fluid ◽  
Turbulent Channel Flows ◽  
The Mean

AbstractSimulation of the 3-D, fully developed turbulent channel flows laden with various mass loading ratios of particles is made using an Eulerian-Lagrangian approach in which the carrier-fluid flow field is solved with a low-Reynolds-number k-ε turbulence model while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. Effects of inter-particle collisions and particle-wall collisions under different extents of wall roughness on particle dispersion are addressed in the study. A cost-effective searching algorithm of collision pair among particles is developed. It is found that the effects of inter-particle collisions on particle dispersion cannot be negligible when the ratio of the mean free time of particle to the mean particle relaxation time of particle is less or equal to O(10). In addition, the wall roughness extent plays an important role in the simulation of particle-wall collisions particularly for cases with small mass loading ratios.

A Modeling Study on Particle Dispersion in Wall-Bounded Turbulent Flows

2014 ◽  
Vol 6 (06) ◽  
pp. 764-782 ◽  
Author(s):  
Jian-Hung Lin ◽  
Keh-Chin Chang
Keyword(s):  
Turbulent Flows ◽  
Particle Dispersion ◽  
Hard Sphere Model ◽  
Wall Roughness ◽  
Mass Loading ◽  
Particle Collisions ◽  
Physical Mechanisms ◽  
Parametric Studies ◽  
Low Mass ◽  
Bounded Particle

AbstractThree physical mechanisms which may affect dispersion of particle’s motion in wall-bounded turbulent flows, including the effects of turbulence, wall roughness in particle-wall collisions, and inter-particle collisions, are numerically investigated in this study. Parametric studies with different wall roughness extents and with different mass loading ratios of particles are performed in fully developed channel flows with the Eulerian-Lagrangian approach. A low-Reynolds-numberk–εturbulence model is applied for the solution of the carrier-flow field, while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. It is shown that the mechanism of inter-particle collisions should be taken into account in the modeling except for the flows laden with sufficiently low mass loading ratios of particles. Influences of wall roughness on particle dispersion due to particle-wall collisions are found to be considerable in the bounded particle–laden flow. Since the investigated particles are associated with large Stokes numbers, i.e., larger thanO(1), in the test problem, the effects of turbulence on particle dispersion are much less considerable, as expected, in comparison with another two physical mechanisms investigated in the study.

A Cost-Effective Search of Collision Pairs in Lagrangian Particle Tracking Method

2015 ◽  
Author(s):  
Jian-Hung Lin ◽  
Keh-Chin Chang
Keyword(s):  
Particle Tracking ◽  
Equations Of Motion ◽  
Cost Effective ◽  
Computational Procedure ◽  
Hard Sphere Model ◽  
Particle Collisions ◽  
Time Step ◽  
Tracking Method ◽  
Particle Tracking Method ◽  
Computational Expenditure

In the simulation of particle-laden flows, in which the inter-particle collisions have to be considered, using the Eulerian-Lagrangian approach, it is agreed that the search of collision pairs based on the deterministic particle tracking method together with the binary-collision, hard-sphere model is a time consuming job in the computational procedure particularly for the flow laden with a remarkably high number density of particles. A cost-effective algorithm for the particle tracking processes which include solving the equations of motion, searching the collision pairs, and updating the list of neighboring particles’ indices is developed. It is demonstrated in the turbulent, fully developed, particle-laden channel flows that the computational expenditure required for completing the particle tracking processes in a given Lagrangian time step can be optimally made with an approximately linear proportionally to the total number of particles (NPT) by setting the number of Lagrangian cells (Ncell) for computation in accordance with the criterion of NPT / Ncell = O(10°).

Structure and Pressure Drop in Particle-Laden Gas Flow Through a Pipe Bend: A Numerical Analysis by the Euler/Lagrange Approach

2009 ◽  
Author(s):  
S. Lai´n ◽  
M. Sommerfeld
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Gas Flows ◽  
Wall Roughness ◽  
Mass Loading ◽  
Particle Collisions ◽  
Pipe Bend ◽  
Flow Through ◽  
Fully Coupled ◽  
Lagrange Approach

The structure of particle-laden gas flows in a horizontal-to-vertical elbow is investigated numerically for analysing the required modelling depth. The numerical computations are performed with the fully coupled Euler-Lagrange approach considering all the relevant forces: drag, gravity-buoyancy and lift forces (slip-shear and slip-rotational). Moreover, interparticle and particle-rough wall collisions are taken into account by means of stochastic approaches. The effect of the different mechanisms, i.e. wall roughness, inter-particle collisions and mass loading, on the flow structure in the bend and the resulting pressure drop are investigated.

scholarly journals Turbulence attenuation in particle-laden flow in smooth and rough channels

2015 ◽  
Vol 773 ◽  
pp. 103-136 ◽  
Author(s):  
A. W. Vreman
Keyword(s):  
Gas Flow ◽  
Point Particle ◽  
Solid Particles ◽  
Spherical Particles ◽  
Wall Roughness ◽  
Particle Collisions ◽  
Wall Unit ◽  
Rough Walls ◽  
The Mean ◽  
Particle Laden Flow

Results of point-particle direct numerical simulations of downward gas–solid flow in smooth and rough vertical channels are presented. Two-way coupling and inter-particle collisions are included. The rough walls are shaped as fixed layers of tiny spherical particles with diameter much smaller than the viscous wall unit. The turbulence attenuation induced by the free solid particles in the gas flow is shown to be enhanced with increasing wall roughness. The so-called feedback force, the force exerted by the free particles on the gas, is decomposed into three contributions: the domain average of the mean feedback force, the non-uniform part of the mean feedback force and the fluctuating part of the feedback force. Since the non-uniformity of the mean feedback force increases with wall roughness, the effect of the non-uniform part of the mean feedback force is investigated in detail. For both smooth and rough walls, the non-uniform part of the mean feedback force is shown to contribute significantly to the particle-induced turbulence attenuation.

scholarly journals Addition of Flucytosine to Fluconazole for the Treatment of Cryptococcal Meningitis in Africa: A Multicountry Cost-effectiveness Analysis

2019 ◽  
Vol 70 (1) ◽  
pp. 26-29 ◽  
Author(s):  
Tinevimbo Shiri ◽  
Angela Loyse ◽  
Lawrence Mwenge ◽  
Tao Chen ◽  
Shabir Lakhi ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Cost Effectiveness ◽  
Cryptococcal Meningitis ◽  
Cost Effective ◽  
Immunodeficiency Virus ◽  
The Mean ◽  
The Cost ◽  
The Impact ◽  
Costing Analysis ◽  
Very High

Abstract Background Mortality from cryptococcal meningitis remains very high in Africa. In the Advancing Cryptococcal Meningitis Treatment for Africa (ACTA) trial, 2 weeks of fluconazole (FLU) plus flucytosine (5FC) was as effective and less costly than 2 weeks of amphotericin-based regimens. However, many African settings treat with FLU monotherapy, and the cost-effectiveness of adding 5FC to FLU is uncertain. Methods The effectiveness and costs of FLU+5FC were taken from ACTA, which included a costing analysis at the Zambian site. The effectiveness of FLU was derived from cohorts of consecutively enrolled patients, managed in respects other than drug therapy, as were participants in ACTA. FLU costs were derived from costs of FLU+5FC in ACTA, by subtracting 5FC drug and monitoring costs. The cost-effectiveness of FLU+5FC vs FLU alone was measured as the incremental cost-effectiveness ratio (ICER). A probabilistic sensitivity analysis assessed uncertainties and a bivariate deterministic sensitivity analysis examined the impact of varying mortality and 5FC drug costs on the ICER. Results The mean costs per patient were US $847 (95% confidence interval [CI] $776–927) for FLU+5FC, and US $628 (95% CI $557–709) for FLU. The 10-week mortality rate was 35.1% (95% CI 28.9–41.7%) with FLU+5FC and 53.8% (95% CI 43.1–64.1%) with FLU. At the current 5FC price of US $1.30 per 500 mg tablet, the ICER of 5FC+FLU versus FLU alone was US $65 (95% CI $28–208) per life-year saved. Reducing the 5FC cost to between US $0.80 and US $0.40 per 500 mg resulted in an ICER between US $44 and US $28 per life-year saved. Conclusions The addition of 5FC to FLU is cost-effective for cryptococcal meningitis treatment in Africa and, if made available widely, could substantially reduce mortality rates among human immunodeficiency virus–infected persons in Africa.

An attempt to detect a neutral particle of small mass

1934 ◽  
Vol 30 (1) ◽  
pp. 59-61 ◽  
Author(s):  
J. Chadwick ◽  
D. E. Lea
Keyword(s):  
Neutral Particle ◽  
Small Mass ◽  
Conservation Of Energy ◽  
The Mean ◽  
Nuclear Processes

It has long been realised that there are difficulties in understanding the continuous β-ray spectra emitted by certain radioactive bodies, if the conservation of energy, as applied to nuclear processes, is to be retained. In the case of radium E, for example, the energy of the disintegration β particles varies from quite low values to about a million volts, the mean being nearly 400,000 volts.

A Novel Nonsurgical Technique for Correcting Congenital Auricular Anomalies

2021 ◽  
Author(s):  
Shay I. Duvdevani ◽  
Hadas Knoller ◽  
Noa Rozendorn ◽  
Eran E. Alon ◽  
Ory Madgar
Keyword(s):  
Treatment Initiation ◽  
Neonatal Period ◽  
Cost Effective ◽  
Normal Appearance ◽  
Time Saving ◽  
Effective Time ◽  
Custom Made ◽  
The Mean ◽  
Ear Anomalies ◽  
Surgical Corrections

AbstractCongenital ear anomalies are associated with psychological morbidity. Ear deformities can usually be corrected by nonsurgical techniques such as splinting or molding in the neonatal period, initiated before 6 weeks. Without early corrections, many will require otoplasty during childhood. We introduce a novel silicone-based custom mold technique for congenital ear anomalies. The highly malleable silicone was pushed into every part of the auricle, enabling the auricle to remain in the desired shape, with new molds made weekly. Of 31 newborns (18 males, 13 females), 54 ears were treated. Average age at treatment initiation was 26.8 days. The mean treatment duration was 43.2 days, with a median of 28 days. Normal appearance and parent's satisfaction were achieved in 30 patients with 49 deformed ears and also in four newborns older than 6 weeks. Three concha type microtia in two patients achieved great improvements and parents' satisfaction. No complications were reported. Marked aesthetic improvements and normal appearance were achieved for all deformed auricles treated, and improvements in the concha type microtia will partially alleviate future surgical corrections. The results are not inferior to other techniques. The advantages are as follows: cost-effective, time-saving, simple to master, no need for hair shaving, and easy use for parents. Patients older than 6 weeks of age achieved normal auricle appearance, enabling the correction in older newborns. Custom made silicone auricle molding offers a simple nonsurgical technique for correcting congenital ear anomalies, alleviating the need for future surgical corrections.

scholarly journals Cost-effectiveness of positive airway pressure modalities in obesity hypoventilation syndrome with severe obstructive sleep apnoea

Thorax ◽  
2020 ◽  
Vol 75 (6) ◽  
pp. 459-467 ◽  
Author(s):  
Juan F Masa ◽  
Babak Mokhlesi ◽  
Iván Benítez ◽  
Francisco Javier Gómez de Terreros Caro ◽  
M-Ángeles Sánchez-Quiroga ◽  
...  
Keyword(s):  
Cost Effectiveness ◽  
Primary Outcome ◽  
Cost Effective ◽  
Sleep Apnoea ◽  
Obesity Hypoventilation Syndrome ◽  
Obstructive Sleep ◽  
The Mean ◽  
Hypoventilation Syndrome ◽  
Obesity Hypoventilation

BackgroundObesity hypoventilation syndrome (OHS) is treated with either non-invasive ventilation (NIV) or CPAP, but there are no long-term cost-effectiveness studies comparing the two treatment modalities.ObjectivesWe performed a large, multicentre, randomised, open-label controlled study to determine the comparative long-term cost and effectiveness of NIV versus CPAP in patients with OHS with severe obstructive sleep apnoea (OSA) using hospitalisation days as the primary outcome measure.MethodsHospital resource utilisation and within trial costs were evaluated against the difference in effectiveness based on the primary outcome (hospitalisation days/year, transformed and non-transformed in monetary term). Costs and effectiveness were estimated from a log-normal distribution using a Bayesian approach. A secondary analysis by adherence subgroups was performed.ResultsIn total, 363 patients were selected, 215 were randomised and 202 were available for the analysis. The median (IQR) follow-up was 3.01 (2.91–3.14) years for NIV group and 3.00 (2.92–3.17) years for CPAP. The mean (SD) Bayesian estimated hospital days was 2.13 (0.73) for CPAP and 1.89 (0.78) for NIV. The mean (SD) Bayesian estimated cost per patient/year in the NIV arm, excluding hospitalisation costs, was €2075.98 (91.6), which was higher than the cost in the CPAP arm of €1219.06 (52.3); mean difference €857.6 (105.5). CPAP was more cost-effective than NIV (99.5% probability) because longer hospital stay in the CPAP arm was compensated for by its lower costs. Similar findings were observed in the high and low adherence subgroups.ConclusionCPAP is more cost-effective than NIV; therefore, CPAP should be the preferred treatment for patients with OHS with severe OSA.Trial registration numberNCT01405976

scholarly journals Inhibition of Cytochrome P450 (CYP450) Isoforms by Isoniazid: Potent Inhibition of CYP2C19 and CYP3A

2001 ◽  
Vol 45 (2) ◽  
pp. 382-392 ◽  
Author(s):  
Zeruesenay Desta ◽  
Nadia V. Soukhova ◽  
David A. Flockhart
Keyword(s):  
Cytochrome P450 ◽  
Liver Microsomes ◽  
Cost Effective ◽  
Competitive Inhibitor ◽  
Inhibitory Effect ◽  
Significant Inhibition ◽  
Specific Substrate ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
The Mean

ABSTRACT Isoniazid (INH) remains the most safe and cost-effective drug for the treatment and prophylaxis of tuberculosis. The use of INH has increased over the past years, largely as a result of the coepidemic of human immunodeficiency virus infection. It is frequently given chronically to critically ill patients who are coprescribed multiple medications. The ability of INH to elevate the concentrations in plasma and/or toxicity of coadministered drugs, including those of narrow therapeutic range (e.g., phenytoin), has been documented in humans, but the mechanisms involved are not well understood. Using human liver microsomes (HLMs), we tested the inhibitory effect of INH on the activity of common drug-metabolizing human cytochrome P450 (CYP450) isoforms using isoform-specific substrate probe reactions. Incubation experiments were performed at a single concentration of each substrate probe at its Km value with a range of INH concentrations. CYP2C19 and CYP3A were inhibited potently by INH in a concentration-dependent manner. At 50 μM INH (∼6.86 μg/ml), the activities of these isoforms decreased by ∼40%. INH did not show significant inhibition (<10% at 50 μM) of other isoforms (CYP2C9, CYP1A2, and CYP2D6). To accurately estimate the inhibition constants (Ki values) for each isoform, four concentrations of INH were incubated across a range of five concentrations of specific substrate probes. The meanKi values (± standard deviation) for the inhibition of CYP2C19 by INH in HLMs and recombinant human CYP2C19 were 25.4 ± 6.2 and 13 ± 2.4 μM, respectively. INH showed potent noncompetitive inhibition of CYP3A (Ki = 51.8 ± 2.5 to 75.9 ± 7.8 μM, depending on the substrate used). INH was a weak noncompetitive inhibitor of CYP2E1 (Ki = 110 ± 33 μM) and a competitive inhibitor of CYP2D6 (Ki = 126 ± 23 μM), but the mean Ki values for the inhibition of CYP2C9 and CYP1A2 were above 500 μM. Inhibition of one or both CYP2C19 and CYP3A isoforms is the likely mechanism by which INH slows the elimination of coadministered drugs, including phenytoin, carbamazepine, diazepam, triazolam, and primidone. Slow acetylators of INH may be at greater risk for adverse drug interactions, as the degree of inhibition was concentration dependent. These data provide a rational basis for understanding drug interaction with INH and predict that other drugs metabolized by these two enzymes may also interact.

scholarly journals The cost of immunising at the general practice level

2009 ◽  
Vol 1 (4) ◽  
pp. 286 ◽  
Author(s):  
Nikki Turner ◽  
Paul Rouse ◽  
Stacey Airey ◽  
Helen Petousis-Harris
Keyword(s):  
General Practice ◽  
Cost Allocation ◽  
Cost Model ◽  
Cost Effective ◽  
Fee For Service ◽  
Activity Based Costing ◽  
Childhood Immunisation ◽  
Practice Nurses ◽  
The Mean ◽  
The Cost

INTRODUCTION: Childhood immunisation is one of the most cost-effective activities in health care. However, New Zealand (NZ) has failed to achieve national coverage targets. NZ general practice is the primary site of service delivery and is funded on a fee-for-service basis for delivery of immunisation events. AIM: To determine the average cost to a general practice of delivering childhood immunisation events and to develop a cost model for the typical practice. METHODS: A purposeful selection of 24 diverse practices provided data via questionnaires and a daily log over a week. Costs were modelled using activity-based costing. RESULTS: The mean time spent on an immunisation activity was 23.8 minutes, with 90.7% of all staff time provided by practice nurses. Only 2% of the total time recorded was spent on childhood immunisation opportunistic activities. Practice nurses spent 15% of their total work time on immunisation activity. The mean estimated cost per vaccination event was $25.90; however, there was considerable variability across practices. A ‘typical practice’ model was developed to better understand costs at different levels of activity. CONCLUSIONS: The current level of immunisation benefit subsidy is considerably lower than the cost of a standard vaccination event, although there is wide variability across practices. The costs of delivery exceeding the subsidy may be one reason why there is an apparently small amount of time spent on extra opportunistic activities and a barrier to increasing efforts to raise immunisation rates. KEYWORDS: Immunisation; vaccination; patient care management; cost analysis; cost allocation

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