Active Control of Passive and Active Particle Distribution at the Outlet of Double Y-Microchannel Using Pulsatile Flow

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Minh Chau Nguyen ◽  
Hassan Peerhossaini ◽  
Elnaz Pashmi ◽  
Mohammad Mehdi Salek ◽  
Mojtaba Jarrahi
Keyword(s):  
Phase Shift ◽  
Pulsatile Flow ◽  
Particle Distribution ◽  
Amplitude Ratio ◽  
Pulsation Period ◽  
Steady Flows ◽  
Control Parameters ◽  
Flow Conditions ◽  
Velocity Amplitude ◽  
Series Of Experiments

Abstract While a variety of active and passive techniques have been proposed for steady flows, pulsatile flow has received much less attention. Pulsation makes more control parameters available for passive methods and enables them to separate particles. The purpose of this work is to determine the effects of the phase shift between two entering flows (only one includes the particles) on particle separation inside a double Y-microchannel. Numerical simulations were carried out for both steady and pulsating flow conditions. The results showed that when the velocity amplitude ratio (β) is less than 2, the separation index increases with the phase shift (φ) and the highest efficiency occurs at φ = 180 deg. A similar trend can be observed for higher values of β only if the pulsation period is short enough. A series of experiments qualitatively validated the numerical results.

Control of Particle Distribution at the Outlet of a Double Y-Microchannel Using Pulsatile Flow

2019 ◽  
Author(s):  
Minh Chau Nguyen ◽  
Hassan Peerhossaini ◽  
Mohammad Mehdi Salek ◽  
Mojtaba Jarrahi
Keyword(s):  
Phase Shift ◽  
Pulsatile Flow ◽  
Particle Distribution ◽  
Amplitude Ratio ◽  
Pulsation Period ◽  
Steady Flows ◽  
Control Parameters ◽  
Flow Conditions ◽  
Velocity Amplitude ◽  
Series Of Experiments

Abstract While a variety of active and passive techniques have been proposed for steady flows, pulsatile flow has received much less attention. Pulsation makes more control parameters available for passive methods and enables them to separate particles. The purpose of this work is to determine the effects of phase shift between two entering flows (only one includes the particles) on particle separation inside a double Y-microchannel. Numerical simulations were carried out for both steady and pulsating flow conditions. The results showed that when the velocity amplitude ratio (β) is less than 2, the separation index increases with the phase shift (φ) and the highest efficiency occurs at φ = 180°. A similar trend can be observed for higher values of β only if the pulsation period is short enough. A series of experiments qualitatively validated the numerical results.

scholarly journals New Ways of Revealing Cepheid Binaries

1993 ◽  
Vol 139 ◽  
pp. 406-407
Author(s):  
L. Szabados
Keyword(s):  
Radial Velocity ◽  
Amplitude Ratio ◽  
Wavelength Dependence ◽  
Light Variation ◽  
Pulsation Period ◽  
Regular Pattern ◽  
Observable Effect ◽  
Velocity Amplitude ◽  
Slope Method ◽  
Classical Cepheids

AbstractTwo methods involving the observed amplitudes of radial velocity and UBVR light variations for classical Cepheids have been analysed, both being implicitly known: their principle is trivial but these methods had not yet been used systematically as indicators of duplicity.The slope method is based on the alteration of the wavelength dependence of the light variation amplitude if either a blue or a red companion is added to the light of the Cepheid. The amplitude ratio (AR) method makes use of the fact that the companion reduces the amplitude of the light variation without observable effect on the pulsational radial velocity amplitude. This means that the ratio of these two amplitudes (Arad.vel./AB) has a larger value for binary Cepheids as compared with the single pulsators.Each method has been applied to more than 100 Cepheids, thus allowing to study how the uncontaminated parameters (amplitude ratio and slope) depend on the pulsation period. Binary Cepheids deviate from the regular pattern in these diagrams, and a number of new binaries can be discovered in this way. The effect of duplicity is revealed by both methods independently for VZ CMa, FM Cas, CR Cep, V402 Cyg, VI154 Cyg, V440 Per and DR Vel.

Complete determination of polarization state in the hard X-ray region

1991 ◽  
Vol 24 (6) ◽  
pp. 982-986 ◽  
Author(s):  
T. Ishikawa ◽  
K. Hirano ◽  
S. Kikuta
Keyword(s):  
Phase Shift ◽  
Linear Polarization ◽  
Amplitude Ratio ◽  
Polarization State ◽  
Perfect Crystal ◽  
Electric Vector ◽  
X Ray ◽  
Complete Determination ◽  
Unpolarized Radiation

A new method for complete determination of polarization state in the hard X-ray region is described. The system consists of a perfect-crystal phase retarder and a linear polarization analyzer. This method gives not only the amplitude ratio of mutually perpendicular electric vector components and the phase shift between them but also the proportion of unpolarized radiation.

A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge

2000 ◽  
Vol 214 (5) ◽  
pp. 655-671 ◽  
Author(s):  
S C M Yu ◽  
J B Zhao
Keyword(s):  
Particle Image Velocimetry ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Flow Condition ◽  
Particle Image ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Flow Conditions ◽  
Image Velocimetry

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.

The Motion of a Flat-Plate Pendulum in a Viscous Fluid

1969 ◽  
Vol 91 (4) ◽  
pp. 1100-1104
Author(s):  
J. P. Ries ◽  
W. G. Harrach
Keyword(s):  
Viscous Fluid ◽  
Flat Plate ◽  
Amplitude Ratio ◽  
Harmonic Oscillation ◽  
Oscillation Period ◽  
Velocity Amplitude ◽  
Boundary Layer Equations ◽  
Light Oil ◽  
Damped Oscillation ◽  
Predicted Values

The motion of an infinite, flat plate undergoing free oscillations as a submerged pendulum in a viscous fluid is analyzed. An analytical solution has been obtained through a simultaneous solution of the equation of motion for the plate, the drag force relationship, and the boundary-layer equations for the case of laminar, incompressible, unsteady flow. Expressions for the displacement and velocity of the plate appear as the sum of a damped harmonic oscillation and a particular solution which decays asymptotically to zero with increasing time. The period and logarithmic decrement are expressed as functions of a single parameter which contains the physical properties of the fluid and dimensions of the system. Predicted values of plate displacement, plate velocity, amplitude ratio, and damped oscillation period are compared to the results of an experimental investigation performed in water and a light oil.

scholarly journals Endothelial cell monolayer formation on a small-diameter vascular graft surface under pulsatile flow conditions

2021 ◽  
Vol 23 (3) ◽  
pp. 101-114
Author(s):  
M. Yu. Khanova ◽  
E. A. Velikanova ◽  
V. G. Matveeva ◽  
E. O. Krivkina ◽  
T. V. Glushkova ◽  
...  
Keyword(s):  
Shear Stress ◽  
Endothelial Cell ◽  
Pulsatile Flow ◽  
Vascular Graft ◽  
Cell Monolayer ◽  
Small Diameter ◽  
Flow Conditions ◽  
Endothelial Cell Culture ◽  
Monolayer Formation ◽  
Whole Transcriptome

Objective: to create a cell-populated small-diameter vascular graft (SDVG) using autologous endothelial cells and extracellular matrix proteins, and to evaluate the efficiency of endothelial cell monolayer formation during shear stress preconditioning in a SDVG.Materials and methods. PHBV/PCL tubular scaffolds of vascular grafts were made by electrospinning from a mixture of polyhydroxybutyrate-valerate (PHBV) copolymer and polycaprolactone (PCL) and modified with fibrin. To populate the graft, an endothelial cell culture was isolated from the blood of patients with coronary heart disease. Phenotyping of endothelial colony-forming cell (ECFC) culture was performed by flow cytometry and immunofluorescence microscopy. Cell proliferative and angiogenic activity were also studied. Cell-populated vascular scaffolds were cultured in a pulsatile flow setup with a final shear stress of 2.85 dyne/cm2. The effect of pulsatile flow on monolayer formation was assessed by immunofluorescence, scanning electron microscopy, atomic force microscopy, and whole-transcriptome RNA sequencing.Results. Under the influence of pulsatile flow, endothelial cells that were seeded into the tubular scaffold showed an increase in the expression level of endothelial profile proteins, focal adhesion and cytoskeleton. In contrast to endothelial cell culture on a vascular graft surface under static conditions, when cultured under pulsatile flow with 2.85 dyne/ cm2 shear stress, endothelial lining cells have an increased ability to adhere and are oriented along the pulsatile flow path. Whole-transcriptome RNA sequencing showed that induced shear stress increased expression levels of differentially expressed genes encoding proteins that ensure vascular development, endothelial integrity, and endothelial metabolism. A protocol for fabrication of a personalized cell-populated biodegradable SDVG under pulsatile flow conditions was developed.Conclusion. The use of autologous fibrin and ECFC culture, as well as shear stress preconditioning, allow to obtain a personalized cell-populated SDVG with continuous functional endothelial monolayer adapted to the flow.

scholarly journals Distribution of Artificial Thrombi Candidates Through Patient-Specific Aortic-Arch Phantoms under Pulsatile Flow Conditions

2021 ◽  
Author(s):  
Marco Testaguzza ◽  
Mehdi Benhassine ◽  
Haroun Frid ◽  
Laurence Gebhart ◽  
Karim Zouaoui Boudjeltia ◽  
...  
Keyword(s):  
Aortic Arch ◽  
Pulsatile Flow ◽  
Patient Specific ◽  
Flow Profile ◽  
In Vitro Test ◽  
Flow Conditions ◽  
Test Bed ◽  
Arch Models ◽  
Artificial Emboli

Abstract Ischemic Stroke is the most frequent type of stroke and is subject to many studies investigating prevention means. Avoiding the difficulties and ethical problems of experimental in-vivo research, in-vitro testing is a convenient way of studying in controlled conditions the morphological impact and mechanical aspects of emboli dynamics. This in-vitro study was performed with two realistic silicone aortic-arch phantoms submitted to physiological pulsatile flow conditions. In the in-vitro test bed, using automatic image tracking and analysis, it was made possible detecting and tracking artificial spherical emboli candidates circulating in the anatomic aortic-arch models under a realistic based-patient blood flow profile. The emboli trajectories as well as their repartition in the different supra-aortic branches are presented for the two aortic-arch geometries obtained from CT scans. Through a statistical analysis performed with several artificial emboli sizes, the experimental study shows that the repartition percentages of the emboli closely follow the flowrate repartition percentages for both aortic-arch models, suggesting that higher flowrates lead to higher concentrations of emboli in a given artery. Sets of human thrombi were also injected and the repartition percentages have been established, giving the same trend as for artificial emboli.

Accuracy of Cotton-Mouton polarimetry in sheared toroidal plasma of circular cross-section

Open Physics ◽  
2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Yury Kravtsov ◽  
Janusz Chrzanowski
Keyword(s):  
Simple Model ◽  
Phase Shift ◽  
Perturbation Method ◽  
Cross Section ◽  
Amplitude Ratio ◽  
Circular Cross Section ◽  
Shear Angle ◽  
Tokamak Plasma ◽  
Toroidal Plasma ◽  
Small Shear

AbstractThe Cotton-Mouton effect in sheared plasma with helical magnetic lines is studied on the basis of the equation for complex amplitude ratio (CAR). A simple model for helical magnetic lines in sheared plasma of toroidal configuration is suggested. The equation for CAR in the sheared plasma is solved by perturbation method, using the small shear angle deviations as is characteristic for tokamak plasma. It is shown that the inaccuracy in polarization measurements caused by deviations of the sheared angle amounts to some percentage of the shearless Cotton-Mouton phase shift. One suggested method is to subtract the “sheared” term, which may improve the accuracy of the Cotton-Mouton measurements in the sheared plasma.

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