A lock exchange flow

1970 ◽  
Vol 42 (4) ◽  
pp. 671-687 ◽  
Author(s):  
I. R. Wood
Keyword(s):  
Boundary Layers ◽  
Single Layer ◽  
Flow Regimes ◽  
Major Elements ◽  
The Other ◽  
Exchange Flow ◽  
Minimum Width ◽  
Stationary Layer ◽  
Virtual Point ◽  
Point Of Intersection

In this paper the interchange flow between two reservoirs connected by a contraction and containing fluid of different densities is considered. The effect of the boundary layers on the floor and walls of the contraction on the depth of flow in the contraction is discussed for the case of single layer flowing from one reservoir to the other. Next the theory for a denser layer plunging under a stationary layer is developed. In this case there is a discontinuity at the point of intersection of the surfaces of the flowing and the stationary fluids and there are three possible flow régimes depending on whether this discontinuity occurs at, downstream of, or upstream of the contraction.Finally, the case where there is an interchange flow with fluid flowing from each reservoir into the other is introduced. This latter theory parallels that developed by Wood (1968) for the case of two layers flowing from one reservoir through a contraction into another reservoir and as in this case there are two points of control, one at the position of minimum width and one (the virtual point of control) away from this position of minimum width.Experiments are described for a single layer flowing through the contraction and the results of these are used to obtain an indication of the accuracy that could be expected from the experiments with the more complicated exchange flow. The experiments with the exchange flow verified the major elements of the theory.

Maximal two-layer exchange over a sill and through the combination of a sill and contraction with barotropic flow

1986 ◽  
Vol 164 ◽  
pp. 53-76 ◽  
Author(s):  
D. M. Farmer ◽  
L. Armi
Keyword(s):  
Surface Layer ◽  
Reverse Flow ◽  
Single Layer ◽  
The Other ◽  
Exchange Flow ◽  
Strait Of Gibraltar ◽  
Exchange Flows ◽  
Barotropic Flow ◽  
Flow Through ◽  
Layer Flow

The analysis of two-layer exchange flow through contractions with a barotropic component treated by Armi & Farmer (1986) is extended to include exchange flows over sills and through a combination of a sill and contraction. It is shown that exchange over a sill is fundamentally different from exchange through a contraction. Control at the sill crest acts primarily through the deeper layer into which the sill projects and only indirectly controls the surface layer. This asymmetry in the control results in asymmetrical flows. The interface depth above the crest is not one half the total depth, as assumed in other studies by analogy with flow through contractions, but is somewhat deeper; the maximal exchange rate is less than for flow through a contraction of equal depth. When both a sill and a contraction are present, the contraction influences control at the sill crest only if it lies between the sill and the source of denser water. The response to barotropic flow is also asymmetrical: the transition to single-layer flow occurs at much lower speeds for a barotropic component in one direction than the other.Results of the analysis are applied to exchange flow through the Strait of Gibraltar, which includes both a sill and a contraction. It is shown that maximal exchange conditions apply throughout part of the tidal cycle, and observations illustrate several of the analytical predictions for barotropic flows, including the formation of fronts, single-layer flow, submaximal exchange and reverse flow.

Prothrombin Time Standardization: Report of the Expert Panel on Oral Anticoagulant Control

1979 ◽  
Vol 42 (04) ◽  
pp. 1073-1114 ◽  
Keyword(s):  
Prothrombin Time ◽  
Expert Panel ◽  
The Other ◽  
Rabbit Brain ◽  
Calibration Constant ◽  
Freeze Dried ◽  
The Mean ◽  
Point Of Intersection ◽  
And Control ◽  
Standardization Report

SummaryIn collaborative experiments in 199 laboratories, nine commercial thromboplastins, four thromboplastins held by the National Institute for Biological Standards and Control (NIBS & C), London and the British Comparative Thromboplastin were tested on fresh normal and coumarin plasmas, and on three series of freeze-dried plasmas. One of these was made from coumarin plasmas and the other two were prepared from normal plasmas; in each series, one plasma was normal and the other two represented different degrees of coumarin defect.Each thromboplastin was calibrated against NIBS&C rabbit brain 70/178, from the slope of the line joining the origin to the point of intersection of the mean ratios of coumarin/normal prothrombin times when the ratios obtained with the two thromboplastins on the same fresh plasmas were plotted against each other. From previous evidence, the slopes were calculated which would have been obtained against the NIBS&C “research standard” thromboplastin 67/40, and termed the “calibration constant” of each thromboplastin. Values obtained from the freeze-dried coumarin plasmas gave generally similar results to those from fresh plasmas for all thromboplastins, whereas values from the artificial plasmas agreed with those from fresh plasmas only when similar thromboplastins were being compared.Taking into account the slopes of the calibration lines and the variation between laboratories, precision in obtaining a patient’s prothrombin time was similar for all thromboplastins.

On exactly self-similar turbulent boundary layers and single-layer scaling

2021 ◽  
Vol 33 (5) ◽  
pp. 055102
Author(s):  
Saurabh S. Patwardhan ◽  
O. N. Ramesh
Keyword(s):  
Boundary Layers ◽  
Single Layer ◽  
Turbulent Boundary Layers ◽  
Self Similar

An example of steady laminar flow at large Reynolds number

1960 ◽  
Vol 9 (4) ◽  
pp. 593-602 ◽  
Author(s):  
Iam Proudman
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Boundary Layers ◽  
Tangential Velocity ◽  
Fluid Flows ◽  
The Other ◽  
Large Reynolds Number ◽  
Rotational Flows ◽  
Flow Domain ◽  
Source Of Information

The purpose of this note is to describe a particular class of steady fluid flows, for which the techniques of classical hydrodynamics and boundary-layer theory determine uniquely the asymptotic flow for large Reynolds number for each of a continuously varied set of boundary conditions. The flows involve viscous layers in the interior of the flow domain, as well as boundary layers, and the investigation is unusual in that the position and structure of all the viscous layers are determined uniquely. The note is intended to be an illustration of the principles that lead to this determination, not a source of information of practical value.The flows take place in a two-dimensional channel with porous walls through which fluid is uniformly injected or extracted. When fluid is extracted through both walls there are boundary layers on both walls and the flow outside these layers is irrotational. When fluid is extracted through one wall and injected through the other, there is a boundary layer only on the former wall and the inviscid rotational flow outside this layer satisfies the no-slip condition on the other wall. When fluid is injected through both walls there are no boundary layers, but there is a viscous layer in the interior of the channel, across which the second derivative of the tangential velocity is discontinous, and the position of this layer is determined by the requirement that the inviscid rotational flows on either side of it must satisfy the no-slip conditions on the walls.

Cocurrent Spontaneous Imbibition In Porous Media With the Dynamics of Viscous Coupling and Capillary Backpressure

SPE Journal ◽  
2018 ◽  
Vol 24 (01) ◽  
pp. 158-177 ◽  
Author(s):  
Pål Østebø Andersen ◽  
Yangyang Qiao ◽  
Dag Chun Standnes ◽  
Steinar Evje
Keyword(s):  
Porous Media ◽  
Relative Permeability ◽  
Flow Regimes ◽  
Spontaneous Imbibition ◽  
The Other ◽  
Countercurrent Flow ◽  
Relative Permeabilities ◽  
Viscous Coupling ◽  
Generalized Model ◽  
Matrix Block

Summary This paper presents a numerical study of water displacing oil using combined cocurrent/countercurrent spontaneous imbibition (SI) of water displacing oil from a water-wet matrix block exposed to water on one side and oil on the other. Countercurrent flows can induce a stronger viscous coupling than during cocurrent flows, leading to deceleration of the phases. Even as water displaces oil cocurrently, the saturation gradient in the block induces countercurrent capillary diffusion. The extent of countercurrent flow may dominate the domain of the matrix block near the water-exposed surfaces while cocurrent imbibition may dominate the domain near the oil-exposed surfaces, implying that one unique effective relative permeability curve for each phase does not adequately represent the system. Because relative permeabilities are routinely measured cocurrently, it is an open question whether the imbibition rates in the reservoir (depending on a variety of flow regimes and parameters) will in fact be correctly predicted. We present a generalized model of two-phase flow dependent on momentum equations from mixture theory that can account dynamically for viscous coupling between the phases and the porous media because of fluid/rock interaction (friction) and fluid/fluid interaction (drag). These momentum equations effectively replace and generalize Darcy's law. The model is parameterized using experimental data from the literature. We consider a water-wet matrix block in one dimension that is exposed to oil on one side and water on the other side. This setup favors cocurrent SI. We also account for the fact that oil produced countercurrently into water must overcome the so-called capillary backpressure, which represents a resistance for oil to be produced as droplets. This parameter can thus influence the extent of countercurrent production and hence viscous coupling. This complex mixture of flow regimes implies that it is not straightforward to model the system by a single set of relative permeabilities, but rather relies on a generalized momentum-equation model that couples the two phases. In particular, directly applying cocurrently measured relative permeability curves gives significantly different predictions than the generalized model. It is seen that at high water/oil-mobility ratios, viscous coupling can lower the imbibition rate and shift the production from less countercurrent to more cocurrent compared with conventional modeling. Although the viscous-coupling effects are triggered by countercurrent flow, reducing or eliminating countercurrent production by means of the capillary backpressure does not eliminate the effects of viscous coupling that take place inside the core, which effectively lower the mobility of the system. It was further seen that viscous coupling can increase the remaining oil saturation in standard cocurrent-imbibition setups.

Annulus Wall Boundary-Layer Measurements in a Four-Stage Compressor

1986 ◽  
Vol 108 (1) ◽  
pp. 2-6 ◽  
Author(s):  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Layer Thickness ◽  
Boundary Layers ◽  
Boundary Layer Thickness ◽  
Tip Clearance ◽  
The Other ◽  
Wall Boundary Layer ◽  
Multistage Compressors ◽  
Full Design

There are few available measurements of the boundary layers in multistage compressors when the repeating-stage condition is reached. These tests were performed in a small four-stage compressor; the flow was essentially incompressible and the Reynolds number based on blade chord was about 5 • 104. Two series of tests were performed; in one series the full design number of blades were installed, in the other series half the blades were removed to reduce the solidity and double the staggered spacing. Initially it was wished to examine the hypothesis proposed by Smith [1] that staggered spacing is a particularly important scaling parameter for boundary layer thickness; the results of these tests and those of Hunter and Cumpsty [2] tend to suggest that it is tip clearance which is most potent in determining boundary-layer integral thicknesses. The integral thicknesses agree quite well with those published by Smith.

Pushmi-Pullyu and the Right Atrium

2011 ◽  
pp. 55-62
Author(s):  
James R. Munis
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Right Ventricle ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
The Other ◽  
Right Atrial ◽  
The One ◽  
The Right ◽  
Point Of Intersection

What does right atrial pressure (PRA) do to cardiac output (CO)? On the one hand, we've been taught that PRA represents preload for the right ventricle. That is, the higher the PRA, the greater the right ventricular output (and, therefore, CO). This is simply an application of Starling's law to the right side of the heart. On the other hand, we've been taught that PRA represents the downstream impedance to venous return (VR) from the periphery. That is, the higher the PRA, the lower the VR, and therefore, the lower the CO. The point of intersection between the 2 curves defines a unique blood flow rate, which is both CO and VR at the same time.

Selective withdrawal from a stably stratified fluid

1968 ◽  
Vol 32 (2) ◽  
pp. 209-223 ◽  
Author(s):  
I. R. Wood
Keyword(s):  
Single Layer ◽  
Layered System ◽  
Volume Discharge ◽  
Layer System ◽  
Minimum Width ◽  
Theoretical Predictions ◽  
Small Rise ◽  
Self Similar ◽  
The One ◽  
Dead Water

In this paper a reservoir connected through a horizontal contraction to a channel is considered. Both the reservoir and the channel are considered to contain a stable multi-layered system of fluids. The conditions under which there is a flow in only one layer, and the depth in this flowing layer decreases continuously from its depth in the reservoir to its depth in the channel, give the maximum discharge that can be obtained with a flow only from this single layer. For this case the volume discharge calculations are carried out at a single section (the section of minimum width). Where there are velocities in only two layers and the depth in each of these layers decreases continuously from their depths in the reservoir to their depths in the channel, the theory involves computations at two sections in the flow. These are the section of minimum width and a section upstream of the position of minimum width (the virtual point of control). For this flow it is shown that the solution is the one in which the velocity and density distributions are self similar and that the depths of the layers at the point of maximum contraction are two-thirds of those far upstream. It is then shown that for any stable continuous or discrete density stratification in the reservoir a self similar solution will satisfy the conditions for the depths of the flowing layers to decrease smoothly from the reservoir to downstream of the contraction. Again the ratio of the depth at the contraction to that far upstream is two-thirds.When there is a very large density difference between the fluid in the lower dead water and that in the lowest flowing streamline then this streamline becomes horizontal and may be considered as a frictionless bed. The flow when the bed is not horizontal but where there is a small rise in the channel at the position of maximum contraction is considered for the case where two discrete layers flow under a volume of dead water. In this case the velocity and density profiles are not self similar.Experiments have been carried out with a contraction in a flume for the withdrawal of two discrete layers from a three layer system and the withdrawal from a fluid with a linear density gradient. In both cases the reservoir and channel bed and hence the lowest streamline was effectively horizontal. These experiments confirmed the theoretical predictions.

Use of a stacked drop manhole for energy dissipation: a case study in Edmonton, Alberta

2009 ◽  
Vol 36 (6) ◽  
pp. 1037-1050 ◽  
Author(s):  
G. Adriana Camino ◽  
David Z. Zhu ◽  
Nallamuthu Rajaratnam ◽  
Manas Shome
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Laboratory Investigation ◽  
Flow Regimes ◽  
Flow Patterns ◽  
The Other ◽  
Inflow Conditions ◽  
Water Depths ◽  
Total Energy Dissipation

This paper reports on a laboratory investigation into the performance of a novel stacked drop manhole design where two identical rectangular manholes are stacked one beside the other but at different heights so that there is a drop in elevation from one to the other. The focus of the study was to estimate the energy dissipation that occurs in such stacked manholes during diverse inflow conditions. Flow regimes inside the structure were identified and the effectiveness of the design was assessed under variable inflow conditions. Total energy dissipation in the stacked manhole was found to range from about 50% to 90%, and the contribution of each manhole chamber to the overall energy dissipation was assessed. A relationship between water depths in the manhole chambers and the corresponding outflow conditions was established. In addition, an analysis of the flow patterns and flow regimes highlighted the relevant parameters involved in the mechanisms of energy dissipation.

Effects of Adjacent Ground Treatment on Site Seismic Response

2011 ◽  
Vol 90-93 ◽  
pp. 1576-1580
Author(s):  
Gang Ge ◽  
Jian Min Liu
Keyword(s):  
Ground Motion ◽  
Single Layer ◽  
Soil Improvement ◽  
Soil Reinforcement ◽  
The Other ◽  
Acceleration Response ◽  
Horizontal Acceleration ◽  
Ground Treatment ◽  
Single Block ◽  
Adjacent Soil

The effect of adjacent soil improvement on ground motion is studied using finite element method, when seismic wave is introduced from the single layer on bedrock. The influence of ground motion on soil reinforcement is analyzed; the impacts of the reinforcement zone width, depth, elastic modulus, and the soil improvement interval on response of the ground motion are also investigated. Study shows: for the same site, when the distance between two adjacent foundation consolidation interval is less than 3 to 4 times the width of the reinforcement area, the interaction acceleration response amplitude of various points on the surface of the two adjacent reinforcement area increased significantly than the single block; within the interval , increasing one of the two adjacent foundation’s width, depth, and the other foundation surface, the horizontal acceleration response will Subsequently enlarged; when the interval between the reinforcement area is greater than the range, this effect is negligible.

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