scholarly journals Separation and Surface Nuclei Effects in a Cavitation Susceptibility Meter

1991 ◽  
Vol 113 (4) ◽  
pp. 695-698 ◽  
Author(s):  
L. d’Agostino ◽  
A. J. Acosta
Keyword(s):  
Laminar Flow ◽  
Flow Velocity ◽  
Flow Separation ◽  
Laser Doppler Velocimeter ◽  
Local Flow ◽  
Applied Tension ◽  
Upstream Pressure ◽  
Finished Glass ◽  
Cavitation Nuclei ◽  
Glass Surfaces

This work is concerned with the effects of flow separation and surface nuclei on the operation of a fixed geometry Cavitation Susceptibility Meter (CSM) with laminar flow. Cavitation is induced under controlled conditions at the throat of a glass venturi tube for the measurement of the active nuclei concentration in water samples as a function of the applied tension. Both cavitation and flow velocity are monitored optically by a Laser Doppler Velocimeter. The throat pressure is determined indirectly from the upstream pressure and the local flow velocity. The results show that laminar flow separation and surface nuclei effects are the most stringent operational limitations. Separation in the diffuser increases the minimum attainable throat pressure above the susceptibility of most cavitation nuclei commonly found in technical waters. Surface nuclei can generate extensive sheet or spot cavitation at relatively high tensions even on optically finished glass surfaces. These phenomena are difficult to eliminate and bring therefore into question the practical utility of CSM’s with laminar flow and fixed geometry for the measurement of the dependence of the cavitating nuclei concentration over wide ranges of the applied tension, as required for cavitation studies.

A Cavitation Susceptibility Meter With Optical Cavitation Monitoring—Part One: Design Concepts

1991 ◽  
Vol 113 (2) ◽  
pp. 261-269 ◽  
Author(s):  
L. d’Agostino ◽  
A. J. Acosta
Keyword(s):  
Flow Velocity ◽  
Laser Doppler Velocimeter ◽  
Data Generation ◽  
Time Data ◽  
Local Flow ◽  
Potential Core ◽  
Operational Conditions ◽  
Design Concepts ◽  
Custom Made ◽  
Upstream Pressure

This work is concerned with the design of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The operation of the Cavitation Susceptibility Meter is analyzed and the main considerations leading to the proposed design are illustrated and critically discussed. The results of this analysis indicate that the operational range is mainly limited by nuclei interference, flow separation and saturation (choking), and suggest to develop a Cavitation Susceptibility Meter where: (a) the flow possesses a laminar potential core throughout the venturi throat section in all operational conditions; (b) the pressure at the venturi throat is determined from the upstream pressure and the local flow velocity; (c) the detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter; (d) a custom-made electronic Signal Processor incorporating a frequency counter is used for real time data generation and temporary storage; (e) a computerized system performs the final acquisition and reduction of the data.

scholarly journals A Cavitation Susceptibility Meter With Optical Cavitation Monitoring—Part Two: Experimental Apparatus and Results

1991 ◽  
Vol 113 (2) ◽  
pp. 270-277 ◽  
Author(s):  
L. d’Agostino ◽  
A. J. Acosta
Keyword(s):  
Flow Velocity ◽  
Water Samples ◽  
Tap Water ◽  
Laser Doppler Velocimeter ◽  
Viscous Effects ◽  
Time Data ◽  
Local Flow ◽  
Potential Core ◽  
Custom Made ◽  
Experimental Apparatus

This work is concerned with the development and operation of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The pressure at the venturi throat is determined from the upstream pressure and the local flow velocity without corrections for viscous effects because the flow possesses a laminar potential core in all operational conditions. The detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter. A custom-made electronic Signal Processor is used for real time data generation and temporary storage and a computerized system for final data acquisition and reduction. The implementation of the whole system is described and the results of the application of the Cavitation Susceptibility Meter to the measurement of the water quality of tap water samples are presented and critically discussed with reference to the current state of knowledge on cavitation inception.

Global response of laminar flow separation to local flow perturbations (review)

2012 ◽  
Vol 19 (1) ◽  
pp. 1-8 ◽  
Author(s):  
A. V. Dovgal ◽  
B. Yu. Zanin ◽  
V. V. Kozlov
Keyword(s):  
Laminar Flow ◽  
Flow Separation ◽  
Local Flow ◽  
Global Response

Effects of Inlet Mass Flow Distribution and Magnitude on Reactant Distribution for PEM Fuel Cells

2005 ◽  
Vol 3 (1) ◽  
pp. 45-50 ◽  
Author(s):  
M. McGarry ◽  
L. Grega
Keyword(s):  
Fuel Cell ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Separation ◽  
Flow Distribution ◽  
Pem Fuel Cells ◽  
Local Flow ◽  
Flow Rates ◽  
Large Active Area ◽  
Mass Flow Rates

The mass flow distribution and local flow structures that lead to areas of reactant starvation are explored for a small power large active area PEM fuel cell. A numerical model was created to examine the flow distribution for three different inlet profiles; blunt, partially developed, and fully developed. The different inlet profiles represent the various distances between the blower and the inlet to the fuel cell and the state of flow development. The partially and fully developed inlet profiles were found to have the largest percentage of cells that are deficient, 20% at a flow rate of 6.05 g/s. Three different inlet mass flow rates (stoichs) were also examined for each inlet profile. The largest percent of cells deficient in reactants is 27% and occurs at the highest flow rate of 9.1 g/s (3 stoichs) for the partially and fully developed turbulent profiles. In addition to the uneven flow distribution, flow separation occurs in the front four channels for the blunt inlet profile at all flow rates examined. These areas of flow separation lead to localized reactant deficient areas within a channel.

scholarly journals HDAC3 is crucial in shear- and VEGF-induced stem cell differentiation toward endothelial cells

2006 ◽  
Vol 174 (7) ◽  
pp. 1059-1069 ◽  
Author(s):  
Lingfang Zeng ◽  
Qingzhong Xiao ◽  
Andriana Margariti ◽  
Zhongyi Zhang ◽  
Anna Zampetaki ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Stem Cell ◽  
Cell Differentiation ◽  
Laminar Flow ◽  
Progenitor Cell ◽  
Stem Cell Differentiation ◽  
Es Cell ◽  
Local Flow ◽  
Proliferation And Differentiation

Reendothelialization involves endothelial progenitor cell (EPC) homing, proliferation, and differentiation, which may be influenced by fluid shear stress and local flow pattern. This study aims to elucidate the role of laminar flow on embryonic stem (ES) cell differentiation and the underlying mechanism. We demonstrated that laminar flow enhanced ES cell–derived progenitor cell proliferation and differentiation into endothelial cells (ECs). Laminar flow stabilized and activated histone deacetylase 3 (HDAC3) through the Flk-1–PI3K–Akt pathway, which in turn deacetylated p53, leading to p21 activation. A similar signal pathway was detected in vascular endothelial growth factor–induced EC differentiation. HDAC3 and p21 were detected in blood vessels during embryogenesis. Local transfer of ES cell–derived EPC incorporated into injured femoral artery and reduced neointima formation in a mouse model. These data suggest that shear stress is a key regulator for stem cell differentiation into EC, especially in EPC differentiation, which can be used for vascular repair, and that the Flk-1–PI3K–Akt–HDAC3–p53–p21 pathway is crucial in such a process.

Fiber-coupled self-mixing diode-laser Doppler velocimeter: technical aspects and flow velocity profile disturbances in water and blood flows

1994 ◽  
Vol 33 (24) ◽  
pp. 5628 ◽  
Author(s):  
M. H. Koelink ◽  
F. F. M. de Mul ◽  
A. L. Weijers ◽  
J. Greve ◽  
R. Graaff ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Diode Laser ◽  
Laser Doppler ◽  
Laser Doppler Velocimeter ◽  
Technical Aspects ◽  
Blood Flows ◽  
Flow Velocity Profile

scholarly journals A system for storage and retrieval of individual cells following flow cytometry.

1979 ◽  
Vol 27 (1) ◽  
pp. 289-292 ◽  
Author(s):  
E R Schildkraut ◽  
M Hercher ◽  
H M Shapiro ◽  
R E Young ◽  
N Matsu ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Laminar Flow ◽  
Flow Velocity ◽  
Biomedical Research ◽  
Flow System ◽  
Observation Point ◽  
Storage And Retrieval ◽  
Coated Film ◽  
A Cell ◽  
Air Cells

A system has been developed to deposit cells in indexed locations on a gelatin-coated film following flow cytometry, allowing the measurements made of individual cells to be correlated with observed morphology or with subsequent microspectrophotometric measurements. Samples are deposited in a continuous track on the film by a deposition nib attached to the flow system below the observation point; laminar flow is preserved by adjusting the tape speed and the flow velocity. Locations of individual cells are indicated by etching the film with a spark triggered by the detection of a cell in the flow cytometer. After deposition, the film is dried by forced warm air. Cells on gelatin may be washed and restained with Papanicolaou and other stains with reasonable preservation of morphology. The system may be used for validation of automated cytodiagnostic procedures based on flow cytometry and for biomedical research.

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