An Analysis of Recirculatory Flow in Gas-Stirred Ladles

2010 ◽  
Vol 81 (10) ◽  
pp. 880-885 ◽  
Author(s):  
K. Krishnapisharody ◽  
G.A. Irons
Keyword(s):  
Recirculatory Flow

scholarly journals Recirculatory Fibrinolytic-Assisted External Ventricular Drainage (EVD) for Intraventricular Hemorrhage

2021 ◽  
Author(s):  
Zhen QIN ◽  
John Ching Kwong Kwok ◽  
Peter Yat Ming Woo ◽  
Carmen Yim ◽  
Chi Hang Chon
Keyword(s):  
Intraventricular Hemorrhage ◽  
Treatment Time ◽  
Ex Vivo ◽  
Obstructive Hydrocephalus ◽  
External Ventricular Drainage ◽  
Ventricular Drainage ◽  
Fibrinolytic Agent ◽  
Recirculatory Flow ◽  
Previous Clinical Trial ◽  
Clinical Trial Results

Abstract Background Elevated intracranial pressure and acute obstructive hydrocephalus secondary to intraventricular hemorrhage (IVH) can be treated by external ventricular drainage (EVD). The treatment time and the risk of EVD-related complications can be reduced with fibrinolytic agents’ instillation via an EVD catheter, but previous clinical trial results did not reveal a significant improvement in terms of long-term functional outcomes. A recirculatory fibrinolytic-assisted EVD system was designed. The clot dissolution effectiveness of the system under different drug dosages and fluid flow rates was tested in an ex vivo model. Results The results showed that the mean clot mass was quickly reduced in an initial fibrinolytic agent dose-independent stage, followed by a dose-dependent stage. Elevating fibrinolytic agent dosages beyond a certain threshold did not contribute to shorter dissolution times. Optimal treatment parameters for such a system were determined. A recirculatory flow rate of 10–18 ml/min with a low-dose of 30 000–60 000 IU of uPA resulted in an 80% clot mass reduction within four hours. Conclusions This recirculating fibrinolytic system is a promising novel modification of conventional IVH treatment that could reduce clot dissolution times and procedure-related complications.

Abstract 154: Hemodynamic Regulation of Tie1 in Aortic Valve Endothelial Cells

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Camryn Johnson ◽  
W. David Merryman
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Aortic Valve ◽  
Protein Expression ◽  
Tyrosine Kinase ◽  
Full Length ◽  
Tyrosine Kinase Receptor ◽  
Shear Stresses ◽  
Mrna Levels ◽  
Recirculatory Flow

During the cardiac cycle, the ventricular side of the aortic valve (ventricularis) is exposed to high shear pulsatile flow, while the aortic side (fibrosa) is exposed to low shear recirculatory flow. The two sides have different transcriptional profiles, likely due to their distinct flow patterns. Tie1 is a mechanically sensitive orphan tyrosine kinase receptor found in endothelial cells (ECs). Tie1 is often found associated with Tie2, a tyrosine kinase receptor involved in EC survival. Tie1 prevents ligand binding to Tie2 until Tie1 is cleaved, via shear stress or other signals. Although studies have shown shear stress cleaves Tie1, none have been done in the aortic valve. Mechanically induced changes in Tie1 expression in the valve may be crucial to understand the effects of the hemodynamics of each side. ECs were isolated from the fibrosa and ventricularis of excised porcine aortic valves. The Flexcell 4000 Tension System was used for strain, and an insert for the Flexcell plates ( A, B, C ) was designed to apply shear stress at the same time. Full length Tie1 protein expression in porcine aortic valvular endothelial cells (pAVECs) decreased ~40% after 15% strain for 24 hours, while cleaved Tie1 endodomain levels increased ( D ). Additionally, qPCR results showed that Tie1 mRNA levels did not decrease as dramatically, also supporting Tie1 cleavage. Full length Tie1 protein expression in pAVECs also decreased ~60% after 7 hours of 10 dynes/cm 2 pulsatile bidirectional shear stress and decreased ~90% after 24 hours of 15% strain combined with 2 dynes/cm 2 pulsatile bidirectional shear stress ( E, F ). Akt, a protein kinase phosphorylated by activated Tie2, showed increased phosphorylation after 15 minutes of strain ( G ), providing evidence that cleaved Tie1 may be activating Tie2. These results show the varying responses in Tie1 expression to different shear stresses and strains and demonstrate that mechanical regulation plays an important role in its signaling in the aortic valve.

The Recirculatory Flow Induced by a Laminar Axisymmetric Jet Issuing From a Wall

1987 ◽  
Vol 109 (3) ◽  
pp. 237-241 ◽  
Author(s):  
W. Schneider ◽  
E. Zauner ◽  
H. Bo¨hm
Keyword(s):  
Point Sources ◽  
Creeping Flow ◽  
Outer Flow ◽  
Axisymmetric Jet ◽  
Submerged Jet ◽  
Viscous Forces ◽  
Recirculatory Flow ◽  
Self Similar ◽  
Infinite Wall ◽  
Main Region

The laminar, axisymmetric, submerged jet issuing from a plane, infinite wall perpendicular to the jet axis is considered at very large distance from the nozzle. Based on previous results of an asymptotic analysis, an approximate analytical solution for the complete flow field is obtained. The structure of the far field is discussed by considering various regions the size of which depends strongly on the Reynolds number. The main region is a toroidal eddy in which both inertial and viscous forces are of importance. Closer to the nozzle there is a slender jet flow with slowly varying momentum flux together with a self-similar viscous outer flow. At larger distances, the flow resembles the creeping flow due to point sources of momentum and mass, with the former decaying more rapidly than the latter as infinity is approached. Analytical predictions of the location of the eddy center compare favorably with experimental and numerical results.

Liquid-metal flow in a system of electrically coupled U-bends in a strong uniform magnetic field

1995 ◽  
Vol 299 ◽  
pp. 73-95 ◽  
Author(s):  
Sergei Molokov ◽  
Robert Stieglitz
Keyword(s):  
Magnetic Field ◽  
Pressure Drop ◽  
Liquid Metal ◽  
Uniform Magnetic Field ◽  
Flow Direction ◽  
Metal Flow ◽  
Three Dimensional ◽  
Recirculatory Flow ◽  
The Magnetic Field ◽  
Very High

Liquid-metal magnetohydrodynamic flow in a system of electrically coupled U-bends in a strong uniform magnetic field is studied. The ducts composing the bends are electrically conducting and have rectangular cross-sections. It has been anticipated that very strong global electric currents are induced in the system, which modify the flow pattern and produce a very high pressure drop compared to the flow in a single U-bend. A detailed asymptotic analysis of flow for high values of the Harmann number (in fusion blanket applications of the order of 103−104) shows that circulation of global currents results in several types of peculiar flow patterns. In ducts parallel to the magnetic field a combination of helical and recirculatory flow types may be present and vary from one bend to another. The magnitude of the recirculatory motion may become very high depending on the flow-rate distribution between the bends in the system. The recirculatory flow may account for about 50% of the flow in all bends. In addition there are equal and opposite jets at the walls parallel to the magnetic field, which are common to any two bends. The pressure drop due to three-dimensional effects linearly increases with the number of bends in a system and may significantly affect the total pressure drop. To suppress this and some other unwelcome tendencies either the ducts perpendicular to the magnetic field should be electrically separated, or the flow direction in the neighbouring ducts should be made opposite, so that leakage currents cancel each other.

Unsteady Deformation and Internal Circulation of a Liquid Drop in a Zero Gravity Uniform Flow

1999 ◽  
Vol 121 (3) ◽  
pp. 665-672 ◽  
Author(s):  
Mohammad Farshchi ◽  
Mohammad Hassan Rahimian
Keyword(s):  
Reynolds Number ◽  
Gas Flow ◽  
Liquid Drop ◽  
Zero Gravity ◽  
Two Phase ◽  
Low Mach Number Limit ◽  
Flow Reynolds Number ◽  
Deformation Dynamics ◽  
Recirculatory Flow ◽  
Accurate Numerical Solution

Numerical simulation of the internal and external flow fields of a liquid drop moving in the surrounding gas are considered. The present work is concerned with the time accurate numerical solution of a two phase flow field at the low Mach number limit with an appropriate volume tracking method to capture motion and deformation of a liquid drop. In particular, deformation of a liquid drop moving with a coflowing gas stream in a zero gravity field is simulated. The effects of the gas flow Reynolds number and drop Weber number on the deformation dynamics of the drop have been investigated. There appears to be a critical gas stream Reynolds number, at moderate drop Weber numbers, below which the coflowing drop takes on an oblate cap shape and above which it forms an arrow head shape. It has been shown that an observer moving with the average velocity of the liquid drop sees interesting recirculatory flow patterns inside the drop.

Some Aspects of Three-Dimensional Cavity Flow

1957 ◽  
Vol 61 (557) ◽  
pp. 345-352
Author(s):  
A. J. Taylor-Russell
Keyword(s):  
Static Pressure ◽  
Three Dimensional ◽  
Cavity Flow ◽  
Wake Flow ◽  
Flat Plates ◽  
Mean Velocity ◽  
Wake Flows ◽  
Low Aspect Ratio ◽  
Recirculatory Flow ◽  
Made In

SummarySome experiments concerned with the wake flows of a number of flat plates of low aspect ratio (Fail, Owen and Eyre) have suggested that for large angles of inclination to the undisturbed stream the wake includes a region of recirculation. The present observations include a detailed study of this region, with particular reference to the wake produced by an equilateral triangular plate, and an attempt is made to explain why the recirculatory flow is found only at angles of incidence greater than 35°. The data includes some wind tunnel measurements of force coefficients, static pressure and mean velocity, and observations of the wake flow made in a smoke tunnel and in a water tunnel.

Simulation of Airflow in an Idealized Emphysematous Human Acinus

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Amitvikram Dutta ◽  
Dragos M. Vasilescu ◽  
James C. Hogg ◽  
A. B. Phillion ◽  
J. R. Brinkerhoff
Keyword(s):  
Wall Motion ◽  
Computational Domain ◽  
Airway Wall ◽  
Flow Rates ◽  
Pulmonary Acinus ◽  
Two Generations ◽  
Recirculatory Flow ◽  
Parametric Studies ◽  
The Individual ◽  
Alveolar Septa

Emphysema is the permanent enlargement of air spaces in the respiratory regions of the lung due to destruction of the inter-alveolar septa. The progressive coalescence of alveoli and alveolar ducts into larger airspaces leads to the disruption of normal airway wall motion and airflow rates within the pulmonary acinus. To contribute to the understanding of the individual effects of emphysema during its earliest stages, computational fluid dynamics (CFD) simulations of airflow in mathematically derived models of the pulmonary acinus were performed. The here generated computational domain consists of two generations of alveolar ducts within the pulmonary acinus, with alveolar geometries approximated as closely packed, 14-sided polygons. Physiologically realistic airflow rates and wall motions were used to study airflow patterns within subsequent generations of alveolar ducts during the inspiratory and expiratory phases of the breathing cycle. The effects of progressive emphysema on the airway wall motion and flow rates were simulated by sequentially removing all alveolar septa within each alveolar duct. Parametric studies were presented to independently assess the relative influence of progressive septal destruction of airway motion and flow rates. The results illustrate that septal destruction lowers the flow resistance through the alveolar ducts but has little influence on the mass transport of oxygen into the alveoli. Septal destruction has a net effect on the flow field by favoring the development of recirculatory flow patterns in individual alveoli.

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