Characterization of the Hydrodynamically Developing Flow in a Microtube Using MTV

2005 ◽  
Vol 127 (5) ◽  
pp. 1003-1012 ◽  
Author(s):  
B. R. Thompson ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Laminar Flow ◽  
Maximum Velocity ◽  
Velocity Profiles ◽  
Measured Velocity ◽  
Molecular Tagging Velocimetry ◽  
Vena Contracta ◽  
Entry Length ◽  
Developing Flow ◽  
Hydrodynamically Developing Flow

Micro-molecular tagging velocimetry (μMTV) has been used to characterize the hydrodynamic developing flow in a microtube inlet with a nominal inner diameter of 180μm. Velocity profile data at 11 axial locations within the hydrodynamic developing region were acquired using the μMTV approach and the results represent the first characterization of hydrodynamically developing pipe flow at the microscale. The uncertainty in measurements of time-averaged velocity profiles ranged from 6% to 7% of the centerline velocity. The uncertainty in instantaneous measurements is in the range 8%–16% of the peak maximum velocity. Data were taken at Reynolds numbers of 60, 100, 140, 290, and 350. The data suggest the formation of a vena contracta with either locally turbulent flow or unsteady laminar flow separation early in the tube for the larger Reynolds (Re) numbers, which is quite different from macroscale experiment or numerical simulation where a vena-contracta is not observed for Re<500. The velocity profiles obtained very near the tube entrance exhibited a uniform velocity core flow surrounded by regions of relatively stagnant fluid in the near wall regions. The size of the inferred recirculation zones, measured velocity rms, and maximum shear rates all exhibit increasing magnitude with increasing Reynolds number. The velocity profiles were observed to evolve in the downstream direction until the classical parabolic distribution existed. The total hydrodynamic entry length agrees well with values published in the literature for laminar flow with a uniform inlet velocity, despite the existence of the observed vena contracta.

Characterization of the Hydrodynamically Developing Flow in a Microtube Using Molecular Tagging Velocimetry

2003 ◽  
Author(s):  
B. R. Thompson ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Laser Beam ◽  
Ultra Violet ◽  
Ccd Camera ◽  
Velocity Profiles ◽  
Molecular Tagging Velocimetry ◽  
Vena Contracta ◽  
Entry Length ◽  
Molecular Tagging ◽  
Developing Flow ◽  
Tracer Molecules

There is a need for increased understanding of the momentum transport phenomena in micro-fluidic geometries to aid in the design and optimization of such devices. Micro-molecular tagging velocimetry (μMTV) has been used to characterize the hydrodynamic developing flow in a microtube with an inner diameter of 180 μm. μMTV is a non-intrusive laser-based technique for obtaining detailed measurements of velocity profiles in flows dominated by a single velocity component. μMTV measurements are made by directing an ultra-violet laser beam into a flow containing phosphorescent tracer molecules. The laser beam excites a line of phosphorescence in the flow. Subsequently, two digital images, separated by a short time delay, of the line are captured by a CCD camera. The displacement of the tracer molecules between the images can be determined from the two images and the velocity of the flow is thus calculated. Velocity profile data at ten axial locations within the hydrodynamic developing region of a 180 μm diameter tube were acquired using the μMTV approach. The uncertainty for these measurements ranged from 1.5% to 5.5% of the center line velocity. Data were taken at Reynolds numbers, Re, of 60, 140, 290, and 340. It was observed that a vena-contracta existed in the first few tube diameters for all Re. The velocity profiles obtained very close to the tube entrance exhibited a uniform velocity core flow surrounded by regions of relatively stagnant fluid in the near wall regions. The profiles evolved in the downstream direction until the classical parabolic distribution was observed. The total hydrodynamic entry length agrees well with values published in the literature for macroscale flows, obtained from numerical simulation.

Micro-Scale Velocity Measurements Using Molecular Tagging Velocimetry: Methodology and Uncertainty

2002 ◽  
Author(s):  
B. R. Thompson ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Correlation Method ◽  
Velocity Profiles ◽  
Line Center ◽  
Flow Measurements ◽  
Measured Velocity ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging ◽  
Micro Scale ◽  
Inside Diameter ◽  
New Applications

Micro-scale fluidic devices are now being designed and manufactured for a host of new applications, and it is certain that new applications will emerge. There is, therefore, a need for increased understanding of the momentum transport phenomena at this scale to aid in the understanding, and design and optimization of such devices. This need is behind the development of new techniques for making flow measurements at the micro-scale. Molecular Tagging Velocimetry (MTV) is a laser-based non-intrusive technique for obtaining detailed measurements of velocity profiles. This paper reports on the extension of the method to microtubes of inside diameter of order 100 µm. Fully developed velocity profile measurements are reported here for a Reynolds number of about 140 in a capillary of inside diameter 148 µm. Two image analysis techniques were compared—the line center method, and the correlation method. It was found that the correlation method produced better results and smaller overall uncertainty. Volumetric flow rate determined from integration of the measured velocity profiles agree with accumulation measurements made over a specified time interval to within 3%; the agreement was usually 1–2%. This work reports on the difficulties encountered in applying MTV at these physical scales, the influence of measurement and analysis parameters on results, and the uncertainty associated with measurements.

Characterization of Na(+)-H+ antiporter activity associated with human cheek epithelial cells

1994 ◽  
Vol 267 (1) ◽  
pp. C84-C93 ◽  
Author(s):  
E. J. McMurchie ◽  
S. L. Burnard ◽  
G. S. Patten ◽  
E. J. Lee ◽  
R. A. King ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Human Subjects ◽  
Maximum Velocity ◽  
Hill Coefficient ◽  
Transport Activity ◽  
Uptake Activity ◽  
Dimethyl Amiloride ◽  
Mouth Wash ◽  
Na Uptake

Na+ transport activity was characterized in human cheek epithelial cells obtained from normotensive adult subjects. The cells were isolated using a mouth-wash procedure and assayed for Na+ uptake using a radioactive (22Na+) rapid filtration assay. Cheek cells displayed proton-dependent Na+ uptake activity that was dependent on the magnitude of the externally directed proton gradient measured using the fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein to determine intracellular pH. Amiloride, ethylisopropylamiloride (EIPA), 5-(N,N-dimethyl)-amiloride, 5-(N-methyl-N-isobutyl)-amiloride (MIA), and 5-(N,N-hexamethylene)-amiloride (NNHA) all inhibited proton-dependent Na+ uptake, with MIA, EIPA, and NNHA being the most potent. The Michaelis constant (Km) for extracellular Na+ was 5.7 mM, while the maximum velocity for Na(+)-H+ antiporter activity was 4.3 nmol Na+.mg protein-1.30s-1. The Km for intracellular H+ was 0.17 microM, with a Hill coefficient of 0.7. Stimulation by ouabain and inhibition by bumetanide of cheek cell proton-dependent Na+ uptake indicated only relatively low activities of Na(+)-K(+)-ATPase and Na(+)-K(+)-2Cl- cotransport, respectively. These results are consistent with the presence of Na(+)-H+ antiporter activity in cheek cells. Cheek cells therefore provide a convenient, relatively noninvasive source of tissue for examining Na(+)-H+ antiporter activity in human subjects.

PIV Measurements of Propeller Flow Field in a Large Cavitation Tunnel

2011 ◽  
Author(s):  
Takayuki Mori ◽  
Risa Kimoto ◽  
Kenji Naganuma
Keyword(s):  
Flow Field ◽  
Velocity Profiles ◽  
Marine Propeller ◽  
Measured Velocity ◽  
Piv Measurements ◽  
Tip Vortices ◽  
Systems Research ◽  
Tracer Particles ◽  
Cavitation Tunnel ◽  
Blade Tip

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.

scholarly journals SEARCHING AND MEASUREMENT OF FUNCTIONAL VOIDS BY MEANS OF GPR TOMOGRAPHY BY THE EXAMPLE OF TWO COLUMNS

2017 ◽  
Vol 13 (1) ◽  
pp. 94-109 ◽  
Author(s):  
Marina S. Sudakova ◽  
Eugeniya B. Terentieva ◽  
Alexey Yu. Kalashnikov
Keyword(s):  
Electromagnetic Waves ◽  
High Quality ◽  
Spherical Void ◽  
Engineering Structures ◽  
Measured Velocity ◽  
Inversion Result ◽  
Single Fold ◽  
Solid Part ◽  
Tomography Method

he present article focuses on GPR tomography method potential aimed at the search of functional voids and estimation of their sizes in engineering structures. The size of voids is assumed to be greater than the wavelength for usable frequency. Two examples of the GPR tomographic survey are examined: 1) a square con-crete pillar with granite coating and a square void in the center, 2) cylindrical granite column with functional spherical void which has iron walls. The following issues are considered in the article: the method, the structure of the acquired data, the picking of wanted waves, the analysis of tomographic inversion result, compared with the result of commonly used single-fold antenna geometry GPR. As a result of the research performed it was demonstrated that GPR tomography represents a good solution for the problem of detection, delineation and characterization of voids inside engineering structures. The velocity of electromagnetic waves propagated within the solid part of the column (concrete and granite) was accurately measured. The measured velocity can be con-sidered to the basis for physical properties estimation, for example humidity, voids ratio etc. The acquired quan-titative results are characterized by high quality and are more reliable compared to the results of single-fold GPR survey.

Characterization of laminar flow in periodic open-cell porous structures

2019 ◽  
Vol 201 ◽  
pp. 397-412 ◽  
Author(s):  
Pedro Jorge ◽  
Miguel A.A. Mendes ◽  
Eric Werzner ◽  
José M.C. Pereira
Keyword(s):  
Laminar Flow ◽  
Porous Structures ◽  
Open Cell

Time-Dependent Laminar Flow in Curved Channels

1970 ◽  
Vol 37 (3) ◽  
pp. 838-843 ◽  
Author(s):  
R. J. Nunge
Keyword(s):  
Laminar Flow ◽  
Pressure Gradient ◽  
Constant Pressure ◽  
Time Dependent ◽  
Pressure Gradients ◽  
Straight Channel ◽  
Curvature Ratio ◽  
Curved Channels ◽  
Developing Flow ◽  
Time Required

The velocity distribution for time-dependent laminar flow in curved channels is derived. The analysis applies to flows with pressure gradients which are arbitrary functions of time. Numerical results are obtained for developing flow due to a constant pressure gradient. Developing flow in a straight channel is also discussed and it is found that the curvature ratio has only a small effect on the time required to reach the fully developed state.

scholarly journals Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

2019 ◽  
Vol 49 (3) ◽  
pp. 827-849 ◽  
Author(s):  
Eunok Yim ◽  
Alexandre Stegner ◽  
Paul Billant
Keyword(s):  
Turbulent Viscosity ◽  
Maximum Velocity ◽  
Stability Limit ◽  
Velocity Profiles ◽  
Instability Criterion ◽  
Marginal Stability ◽  
Vertical Wavelength ◽  
Centrifugal Instability ◽  
Wide Range ◽  
Anticyclonic Eddies

AbstractWe investigate the linear stability of intense baroclinic anticyclones, with a particular focus on the centrifugal (inertial) instability. Various vertical and radial velocity profiles are studied. The vertical profiles are such that the velocity is maximum at the surface. These profiles correspond to oceanic eddies such as submesoscale mixed-layer eddies or intense mesoscale eddies in the upper thermocline. The results show that the main characteristics of the centrifugal instability (growth rate, vertical wavelength) depend weakly on the baroclinic structure of the anticyclone. The dominant azimuthal wavenumber is for small Burger number (Bu) and for higher Bu, where Bu is the square root of the ratio of the deformation radius over the characteristic eddy radius where the velocity is maximum. The marginal stability limits of the centrifugal instability for the different velocity profiles collapse approximately on a single curve in the parameter space (Ro, Bu), where is the Rossby number, with being the maximum velocity. By means of an asymptotic analysis for short vertical wavelength, an explicit prediction for the marginal stability limit is derived for a wide range of velocity profiles. We then suggest to use, for most of oceanic anticyclones, the instability criterion valid for a Gaussian eddy: where is the Ekman number, H is the eddy depth, and ν is the turbulent viscosity at the ocean surface. Some baroclinic anticyclones can remain stable even if they have a core region of negative absolute vorticity provided that they are small enough. This formula explains the few observations of intense anticyclonic eddies having a negative core vorticity around .

Maximum Velocity Location and Pressure Drop of Fully Developed Laminar Flow in Circular Sector Ducts

1989 ◽  
Vol 111 (4) ◽  
pp. 1085-1087 ◽  
Author(s):  
Q. M. Lei ◽  
A. C. Trupp
Keyword(s):  
Pressure Drop ◽  
Laminar Flow ◽  
Maximum Velocity ◽  
Circular Sector
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