Thin-Film Coupled Fluid-Solid Analysis of Flow Through the Ahmed™ Glaucoma Drainage Device

2005 ◽  
Vol 127 (5) ◽  
pp. 776-781 ◽  
Author(s):  
Matthew S. Stay ◽  
Tingrui Pan ◽  
J. David Brown ◽  
Babak Ziaie ◽  
Victor H. Barocas
Keyword(s):  
Pressure Drop ◽  
Aqueous Humor ◽  
Flow Rate ◽  
Glaucoma Drainage Device ◽  
Direct Result ◽  
Variable Resistance ◽  
Drainage Device ◽  
Aqueous Humor Flow ◽  
Wide Range ◽  
Flow Through

The Ahmed™ glaucoma valve (AGV) is a popular glaucoma drainage device, allowing maintenance of normal intraocular pressure in patients with reduced trabecular outflow facility. The uniquely attractive feature of the AGV, in contrast to other available drainage devices, is its variable resistance in response to changes in flow rate. As a result of this variable resistance, the AGV maintains a pressure drop between 7 and 12mmHg for a wide range of aqueous humor flow rates. In this paper, we demonstrate that the nonlinear behavior of the AGV is a direct result of the flexibility of the valve material. Due to the thin geometry of the system, the leaflets of the AGV were modeled using the von Kármán plate theory coupled to a Reynolds lubrication theory model of the aqueous humor flow through the valve. The resulting two-dimensional coupled steady-state partial differential equation system was solved by the finite element method. The Poisson’s ratio of the valve was set to 0.45, and the modulus was regressed to experimental data, giving a best-fit value 4.2MPa. Simulation results compared favorably with previous experimental studies and our own pressure-drop∕flow-rate data. For an in vitro flow of 1.6μL∕min, we calculated a pressure drop of 5.8mmHg and measured a pressure drop of 5.2±0.4mmHg. As flow rate was increased, pressure drop rose in a strongly sublinear fashion, with a flow rate of 20μL∕min giving a predicted pressure drop of only 10.9mmHg and a measured pressure drop of 10.5±1.1mmHg. The AGV model was then applied to simulate in vivo conditions. For an aqueous humor flow rate of 1.5-3.0μL∕min, the calculated pressure drops were 5.3 and 6.3mmHg.

Study of fluid flow through a channel deformed by piezoelement

2018 ◽  
Vol 13 (3) ◽  
pp. 1-10 ◽  
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh Nasibullaeva ◽  
O.V. Darintsev
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Boundary Conditions ◽  
Flow Rate ◽  
Contact Surface ◽  
Piezoelectric Element ◽  
Neumann Boundary ◽  
Differential Pressure ◽  
Physical Parameters ◽  
Flow Through

The flow of a liquid through a tube deformed by a piezoelectric cell under a harmonic law is studied in this paper. Linear deformations are compared for the Dirichlet and Neumann boundary conditions on the contact surface of the tube and piezoelectric element. The flow of fluid through a deformed channel for two flow regimes is investigated: in a tube with one closed end due to deformation of the tube; for a tube with two open ends due to deformation of the tube and the differential pressure applied to the channel. The flow rate of the liquid is calculated as a function of the frequency of the deformations, the pressure drop and the physical parameters of the liquid.

Advances in Fisheries Bioengineering

2008 ◽  
Keyword(s):  
Common Carp ◽  
Striped Bass ◽  
Flow Rate ◽  
Lepomis Macrochirus ◽  
Osmerus Mordax ◽  
Rainbow Smelt ◽  
Test Species ◽  
Wide Range ◽  
Flow Through ◽  
Pair Wise Comparison

Abstract.—Aquatic Filter Barrier (AFB) is a permeable fabric material used to reduce the entrainment of ichthyoplankton at water intakes. To determine the potential for this material to protect a wide range of species, we evaluated the retention and survival of the early life stages of common carp <em>Cyprinus carpio</em>, rainbow smelt <em>Osmerus mordax</em>, white sucker <em>Catostomus commersonii</em>, striped bass <em>Morone saxatilis</em>, and bluegill <em>Lepomis macrochirus </em>exposed to AFB fabric in the laboratory. Twelve flow-through testing apparatuses were used in a closed-loop system to evaluate two flow rates (0.04 L/min/cm2) and 0.08 L/min/cm2) and three sizes of fabric perforation (0.5, 1.0, and 1.5 mm) with each species. The results indicate that, with one exception (pair-wise comparison of bluegill survival between 1.0-mm and 1.5- mm perforations; <em>p </em>= 0.0481), survival of organisms was not significantly correlated (<em>p </em>≤ 0.05) to either flow rate or perforation size. Retention of organisms decreased significantly with increasing flow rate for one species of fish (pair-wise comparison of rainbow smelt between 0.04 and 0.08 L/min/cm<sup>2</sup>; <em>p </em>= 0.0084). In addition, larger perforation sizes resulted in significant decreases in retention for three of the test species (common carp, rainbow smelt, and striped bass; <em>p </em>≤ 0.05). Consequently, the potential effectiveness AFB material is reduced by the use of larger perforation sizes. Provided that the material can be maintained and perforation sizes remain small (0.5 mm), AFB should prevent the entrainment of the majority of the organisms of the species tested in the laboratory.

Lateral-Flow Effect on Endwall Heat Transfer and Pressure Drop in a Pin-Fin Trapezoidal Duct of Various Pin Shapes

2000 ◽  
Vol 123 (1) ◽  
pp. 133-139 ◽  
Author(s):  
Jenn-Jiang Hwang ◽  
Chau-Ching Lu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Lateral Flow ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Flow Reynolds Number ◽  
Outlet Flow ◽  
Flow Through

The effects of lateral-flow ejection 0<ε<1.0, pin shapes (square, diamond, and circular), and flow Reynolds number (6000<Re<40,000) on the endwall heat transfer and pressure drop for turbulent flow through a pin-fin trapezoidal duct are studied experimentally. A staggered pin array of five rows and five columns is inserted in the trapezoidal duct, with the same spacings between the pins in the streamwise and spanwise directions: Sx/d=Sy/d=2.5. Three different-shaped pins of length from 2.5<l/d<4.6 span the distance between two endwalls of the trapezoidal duct. Results reveal that the pin-fin trapezoidal duct with lateral-flow rate of ε=0.3-0.4 has a local minimum endwall-averaged Nusselt number and Euler number for all pin shapes investigated. The trapezoidal duct of lateral outlet flow only (ε=1.0) has the highest endwall heat transfer and pressure drop. Moreover, the square pin results in a better heat transfer enhancement than the diamond pin, and subsequently than the circular pin. Finally, taking account of the lateral-flow rate and the flow Reynolds number, the work develops correlations of the endwall-averaged heat transfer with three different pin shapes.

Viscous flow in a cylindrical tube containing a line of spherical particles

1969 ◽  
Vol 38 (1) ◽  
pp. 75-96 ◽  
Author(s):  
Henry Wang ◽  
Richard Skalak
Keyword(s):  
Pressure Drop ◽  
Cylindrical Tube ◽  
Tube Diameter ◽  
Creeping Flow ◽  
Spherical Particles ◽  
Sphere Diameter ◽  
Wide Range ◽  
Mean Pressure ◽  
Order Of Magnitude ◽  
Flow Through

The viscous, creeping flow through a cylindrical tube of a liquid, which contains rigid, spherical particles, is investigated analytically. The spheres are located on the axis of the cylinder and are equally spaced. Solutions are derived for particles in motion and fixed, with and without fluid discharge. Numerical results are presented for the drag on each sphere and the mean pressure drop for a wide range of sizes and spacings of the spheres. The study is motivated by possible application to blood flow in capillaries, where red blood cells represent particles of the same order of magnitude as the diameter of the capillary itself. The results may also be of interest in other applications, such as sedimentation and fluidized beds. It is shown that there is little interaction between particles if the spacing is more than one tube diameter, and that the additional pressure drop over that for Poiseuille flow is less than 50% if the sphere diameter is less than 0·8 of the tube diameter.

Lateral-Flow Effect on Endwall Heat Transfer and Pressure Drop in a Pin-Fin Trapezoidal Duct of Various Pin Shapes

2000 ◽  
Author(s):  
Jenn-Jiang Hwang ◽  
Chau-Ching Lu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Lateral Flow ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Flow Reynolds Number ◽  
Outlet Flow ◽  
Flow Through

Effects of the lateral-flow ejection (0 ≦ ε ≦ 1.0), pin shapes (square, diamond and circular) and flow Reynolds number (6,000 ≦ Re ≦ 40,000) on the endwall heat transfer and pressure drop for turbulent flow through a pin-fin trapezoidal duct are studied experimentally. The trapezoidal duct are inserted with a staggered pin array of five rows and five columns, with the same spacings between the pins in streamwise and spanwise directions of Sx/d = Sy/d = 2.5. Three different-shaped pins of length from 2.5 < l/d < 4.6 span the distance between two endwalls of the trapezoidal duct. Results reveal that the pin-fin trapezoidal duct with a lateral-flow rate of ε = 0.3–0.4 has a local minimum endwall-averaged Nusselt number and Euler number for all pin shapes investigated. The trapezoidal duct of lateral outlet flow only (ε = 1.0) has the highest endwall heat transfer and pressure drop. Moreover, the square pin performs a better heat transfer enhancement than the diamond pin, and subsequently than the circular pin. Finally, taking account of the lateral-flow rate and the flow Reynolds number develops correlations of the endwall-averaged heat transfer for three different pin shapes.

scholarly journals Variation of Pressure Drop along the Straight and Bifurcated Channel: Experiment and Simulation

2019 ◽  
Vol 8 (12) ◽  
pp. 2728-2731
Keyword(s):  
Pressure Drop ◽  
Laminar Flow ◽  
Aspect Ratio ◽  
Computational Model ◽  
Flow Rate ◽  
Normal Water ◽  
Flow Through ◽  
Experiment And Simulation

This paper derives an experimental and simulated investigation carried to analyze the performance of channel for calculating the pressure drop in laminar flow through rectangular shaped (straight and branched) microchannels. The microchannels taken ranged in variable aspect ratio from 0.75 to 1. Every check piece was made from copper and contained only one channel along a direction. The experiments were conducted with normal water, with Reynolds range starting from some 720 to 3500. Predictions obtained supported that with the variation in the aspect ratio the properties of the fluid also change. It is observed that the pressure drop changes with the change in the aspect ratio and flow rate and found that there is a correlation between the experimental and computational model results.

scholarly journals Hydraulic characteristic of collagen

2016 ◽  
Vol 33 (No. 5) ◽  
pp. 479-485 ◽  
Author(s):  
R. Žitný ◽  
A. Landfeld ◽  
J. Skočilas ◽  
J. Stancl ◽  
V. Flegl ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Limited Range ◽  
Hydraulic Characteristic ◽  
Hydraulic Characteristics ◽  
Flow Rates ◽  
Transient Flows ◽  
Wide Range ◽  
On Line ◽  
Collagenous Material

Hydraulic characteristic of collagen. Czech J. Food Sci., 33: 479&ndash;485. The hysteresis of a hydraulic characteristic while pumping an aqueous solution of collagen through a pipe at gradually increasing and decreasing flow rates (hysteresis means that the pressure drop curve during increased flow rate is above the pressure drop during decreasing flow rate) was observed. The problem was initiated by industry and by demand for an on-line recording of rheological properties of collagenous material used for extrusion of collagen casings. The Herschel-Bulkley rheological model was capable to describe rheograms in a wide range of deformation rates; however it was not able to describe and explain the hysteresis. As a possible reason thixotropic properties were identified and the hydraulic characteristic was calculated using a thixotropic generalisation of the Herschel-Bulkley model. The developed 1D numerical model can be applied for on-line modelling of transient flows of incompressible thixotropic food materials (startup flow) and at a limited range of flow rates it is also capable to describe the hysteresis of hydraulic characteristics.

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