Flow in groovy curved channels with thin gap

2020 ◽  
Vol 98 (12) ◽  
pp. 1108-1118
Author(s):  
Nnamdi Fidelis Okechi ◽  
Saleem Asghar
Keyword(s):  
Pressure Gradient ◽  
Phase Difference ◽  
Transverse Flow ◽  
Radius Of Curvature ◽  
Curved Channels ◽  
Small Width ◽  
Axial Pressure Gradient ◽  
Flow Through ◽  
Flow Directions ◽  
Channel Curvature

A pressure-driven viscous flow through groovy curved channels of small width compared to the groove wavelength is studied. The Reynolds number is assumed to be very small, such that the flow is dominated by the viscous and the pressure-gradient forces. The effects of the channel geometry on the inertial free flow are analyzed. Two distinct flow directions are considered: (i) flow transverse to the grooves and (ii) flow longitudinal to the grooves. The velocities for both flow directions are obtained, and their distributions are found to be significantly affected by the grooves and channel curvature. The axial pressure gradient for the transverse flow is examined as a function of the amplitude and the phase difference. The results further indicate that the flow rate can be increased by the grooves for longitudinal flow, irrespective of the phase difference, unlike transverse flow This is because the latter is more affected by grooves for the same radius of curvature and phase difference.

Flow in Narrow Curved Channels

1980 ◽  
Vol 47 (1) ◽  
pp. 7-10 ◽  
Author(s):  
C.-Y. Wang
Keyword(s):  
Exact Solution ◽  
Pressure Gradient ◽  
Wave Number ◽  
Perturbation Scheme ◽  
Arc Length ◽  
Flow Rates ◽  
Circular Arc ◽  
Curved Channels ◽  
Flow Through ◽  
Small Periodic

The flow through narrow, arbitrarily curved channels is formulated using intrinsic coordinates. An exact solution exists for constant curvature or circular arc boundaries. A perturbation scheme is used for the case of small, periodic curvature. The velocities and flow rates depend on both the curvature amplitude and the wave number. It is found that for a given pressure gradient per arc length, the flow may be larger for periodically curved channels than that of straight channels.

Interfacial dynamics of stationary gas bubbles in flows in inclined tubes

1999 ◽  
Vol 398 ◽  
pp. 225-244 ◽  
Author(s):  
DANIEL P. CAVANAGH ◽  
DAVID M. ECKMANN
Keyword(s):  
Pressure Gradient ◽  
Bubble Size ◽  
Contact Angle Hysteresis ◽  
Gas Bubbles ◽  
Solid Material ◽  
Contact Forces ◽  
Tube Material ◽  
Experimental Conditions ◽  
Axial Pressure Gradient ◽  
Inclination Angles

We have experimentally examined the effects of bubble size (0.4 [les ] λ [les ] 2.0), inclination angle (0° [les ] α [les ] 90°), and tube material on suspended gas bubbles in flows in tubes for a range of Weber (0 [les ] We [les ] 3.6), Reynolds (0 [les ] Re [les ] 1200), and Froude (0 [les ] Frα [les ] 1) numbers. Flow rates and associated pressure differences which allow the suspension of bubbles in glass and acrylic tubes are measured. Due to contact angle hysteresis, bubbles which dry the tube wall (i.e. form a gas–solid interface) may remain suspended over a range of flows while non-drying bubbles remain stationary for a single flow rate depending on experimental conditions. Stationary bubbles increase the axial pressure gradient with larger bubbles and steeper inclination angles leading to the greatest increase in the pressure gradient. Both the suspension flow range and pressure difference modifications are strongly dependent upon gas/liquid/solid material interactions. Stronger contact forces, i.e. smaller spreading coefficients, cause dried bubbles in acrylic tubes to remain stationary over a wider range of suspension flows than bubbles in glass tubes. Bubble deformation is governed by the interaction of interfacial, contact, and flow-derived forces. This investigation reveals the importance of bubble size, tube inclination, and tube material on gas bubble suspension.

Hemodynamic Method to Predict Whether Hunterian Ligation of the Basilar Artery Will Lead to Thrombosis of Basilar Bifurcation Aneurysms

Neurosurgery ◽  
1987 ◽  
Vol 20 (2) ◽  
pp. 249-253 ◽  
Author(s):  
Jack Chang ◽  
Margot R. Roach
Keyword(s):  
Pressure Gradient ◽  
Basilar Artery ◽  
Diameter Ratio ◽  
Phase Lag ◽  
Maximal Width ◽  
Before And After ◽  
Simple Measurement ◽  
Flow Through ◽  
Stop Flow

Abstract In some cases, basilar artery aneurysms cannot be repaired surgically and the basilar artery is occluded near the neck of the aneurysm to stop flow into the aneurysm. After the operation, the aneurysm can fill only by flow through the posterior communicating arteries (PCoAs). Hemodynamically, if the flow were the same in both PCoAs and there were no phase lag in the pressures, there would be no pressure gradient for flow to go across the neck of the aneurysm and therefore the aneurysm would thrombose. We have assumed that the diameter of the artery is roughly proportional to the flow that goes through it chronically. We measured the diameters of the PCoAs in 25 patients who had hunterian ligation of the basilar artery. We also measured the maximal width, height, and depth of the aneurysms on angiograms obtained before and after operation. Eleven aneurysms thrombosed completely and had a diameter ratio of > 0.6; 10 aneurysms thrombosed partially and had a diameter ratio of 0.46 ˜ 1.0; 4 aneurysms did not change and had a diameter ratio of <0.45. The ratio of the sizes of the PCoAs pre- and postoperatively was comparable in most cases, so we believe that it is possible to predict reasonably accurately from this simple measurement whether the aneurysm is likely to thrombose if the basilar artery is ligated.

A Topological Study of the Genesis of a Horseshoe Vortex in the Symmetry Plane Due to an Adverse Pressure Gradient

2001 ◽  
Author(s):  
Martijn A. van den Berg ◽  
Michael M. J. Proot ◽  
Peter G. Bakker
Keyword(s):  
Pressure Gradient ◽  
Bifurcation Theory ◽  
Nonlinear Differential Equations ◽  
Nonlinear Dynamical System ◽  
Symmetry Plane ◽  
Adverse Pressure Gradient ◽  
Horseshoe Vortex ◽  
Nonlinear Dynamical ◽  
Separating Flow ◽  
Flow Through

Abstract The present paper describes the genesis of a horseshoe vortex in the symmetry plane in front of a juncture. In contrast to a previous topological investigation, the presence of the obstacle is no longer physically modelled. Instead, the pressure gradient, induced by the obstacle, has been used to represent its influence. Consequently, the results of this investigation can be applied to any symmetrical flow above a flat plate. The genesis of the vortical structure is analysed by using the theory of nonlinear differential equations and the bifurcation theory. In particular, the genesis of a horseshoe vortex can be described by the unfolding of the degenerate singularity resulting from a Jordan Normal Form with three vanishing eigenvalues and one linear term which is related to the adverse pressure gradient. The examination of this nonlinear dynamical system reveals that a horseshoe vortex emanates from a non-separating flow through two subsequent saddle-node bifurcations in different directions and the transition of a node into a focus located in the flow field.

scholarly journals The structure and dynamics of patch-clamped membranes: a study using differential interference contrast light microscopy.

1990 ◽  
Vol 111 (2) ◽  
pp. 599-606 ◽  
Author(s):  
M Sokabe ◽  
F Sachs
Keyword(s):  
Cell Surface ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
Radius Of Curvature ◽  
Pressure Gradients ◽  
Structure And Motion ◽  
Excised Patches ◽  
Glass Interface ◽  
Pipette Tip ◽  
Flow Through

We have developed techniques for micromanipulation under high power video microscopy. We have used these to study the structure and motion of patch-clamped membranes when driven by pressure steps. Patch-clamped membranes do not consist of just a membrane, but rather a plug of membrane-covered cytoplasm. There are organelles and vesicles within the cytoplasm in the pipette tip of both cell-attached and excised patches. The cytoplasm is capable of active contraction normal to the plane of the membrane. With suction applied before seal formation, vesicles may be swept from the cell surface by shear stress generated from the flow of saline over the cell surface. In this case, patch recordings are made from membrane that was not originally present under the tip. The vesicles may break, or fuse and break, to form the gigasealed patch. Patch membranes adhere strongly to the wall of the pipette so that at zero transmural pressure the membranes tend to be normal to the wall. With transmural pressure gradients, the membranes generally become spherical; the radius of curvature decreasing with increasing pressure. Some patches have nonuniform curvature demonstrating that forces normal to the membrane may be significant. Membranes often do not respond quickly to changes in pipette pressure, probably because viscoelastic cytoplasm reduces the rate of flow through the tip of the pipette. Inside-out patches may be peeled from the walls of the pipette, and even everted (with positive pressure), without losing the seal. This suggests that the gigaseal is a distributed property of the membrane-glass interface.

Laminar flow in symmetrical channels with slightly curved walls II. An asymptotic series for the stream function

1963 ◽  
Vol 272 (1350) ◽  
pp. 406-428 ◽  
Keyword(s):  
Laminar Flow ◽  
Asymptotic Series ◽  
Radius Of Curvature ◽  
Two Dimensional ◽  
The Third ◽  
Higher Order Terms ◽  
Curvature Parameter ◽  
Leading Term ◽  
Flow Through ◽  
Curved Walls

A class of two-dimensional channels, with walls whose radius of curvature is uniformly large relative to local channel width, is described, and the velocity field of laminar flow through these channels is obtained as a power series in the small curvature parameter. The leading term is the Jeffery-Hamel solution considered in part I, and it is shown here how the higher-order terms are found. Terms of the third approximation have been computed. The theory is applied to two examples, for one of which experimental results are available and confirm the theoretical values with fair accuracy.

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