Direct and reverse flow-through heterogeneous scintillation counting of radiolabelled amino acids using post-column solvent segmentation

1990 ◽  
Vol 508 ◽  
pp. 301-308 ◽  
Author(s):  
A.C. Veltkamp ◽  
H.A. Das ◽  
U.A.Th. Brinkman
Keyword(s):  
Amino Acids ◽  
Reverse Flow ◽  
Scintillation Counting ◽  
Flow Through ◽  
Radiolabelled Amino Acids

Fluid Particle Motion and Lagrangian Velocities for Pulsatile Flow Through a Femoral Artery Branch Model

1987 ◽  
Vol 109 (1) ◽  
pp. 94-101 ◽  
Author(s):  
M. R. Back ◽  
Y. I. Cho ◽  
D. W. Crawford ◽  
L. H. Back
Keyword(s):  
Femoral Artery ◽  
Flow Separation ◽  
Pulsatile Flow ◽  
Reverse Flow ◽  
Branch Model ◽  
Flow Features ◽  
Flow Phase ◽  
Flow Through ◽  
Artery Flow ◽  
Artery Branch

A flow visualization study using selective dye injection and frame by frame analysis of a movie provided qualitative and quantitative data on the motion of marked fluid particles in a 60 degree artery branch model for simulation of physiological femoral artery flow. Physical flow features observed included jetting of the branch flow into the main lumen during the brief reverse flow period, flow separation along the main lumen wall during the near zero flow phase of diastole when the core flow was in the downstream direction, and inference of flow separation conditions along the wall opposite the branch later in systole at higher branch flow ratios. There were many similarities between dye particle motions in pulsatile flow and the comparative steady flow observations.

Reverse Flow Pressure Limiting Aperture

2000 ◽  
Vol 6 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Gerasimos D. Danilatos
Keyword(s):  
Pressure Difference ◽  
Gas Flow ◽  
Reverse Flow ◽  
Gas Jet ◽  
The Third ◽  
The Core ◽  
Annular Aperture ◽  
Flow Through ◽  
Flow Pressure ◽  
Gas Molecules

The reverse flow pressure limiting aperture is a device that creates and sustains a substantial gas pressure difference between two chambers connected via an aperture. The aperture is surrounded by an annular orifice leading to a third chamber. The third chamber is maintained at a relatively high pressure that forces gas to flow through the annular aperture into the first of said two chambers. The ensuing gas flow develops into a supersonic annular gas jet, the core of which is coaxial with the central aperture. A pumping action is created at the core of the jet and any gas molecules leaking through the aperture from the second chamber are entrained and forced into the first chamber, thus creating a substantial pressure difference between the first and second chamber.

Vortex Detachment and Reverse Flow in Pulsatile Laminar Flow Through Axisymmetric Sudden Expansions

1999 ◽  
Vol 121 (3) ◽  
pp. 574-579 ◽  
Author(s):  
S. Tavoularis ◽  
R. K. Singh
Keyword(s):  
Reynolds Number ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Flow Region ◽  
Vortex Rings ◽  
Mean Velocity ◽  
Zone Length ◽  
Deceleration Phase ◽  
Pulsatile Flows ◽  
Flow Through

Incompressible, steady and pulsatile flows in axisymmetric sudden expansions with diameter ratios of 1:2.25 and 1:2.00 have been simulated numerically over the ranges of time-averaged bulk Reynolds number 0.1 ≤ Re ≤ 400 and Womersley number 0.1 ≤ W ≤ 50. For steady flow, the calculated recirculation zone length increased linearly with an increase in Re, in good agreement with earlier experiments. For pulsatile flows, particularly at higher values of W, the recirculation zone length correlated strongly with the acceleration of the flow and not with the instantaneous Reynolds number; it increased during the deceleration phase and decreased during the acceleration phase. The computed mean velocity and reattachment length were in general agreement with published experimental data. At relatively low W, the computed near-wall, reverse flow region extended along the full domain over part of the cycle, similarly to that in the experiments. At low values of W, the vortex rings created at the expansion remained attached and oscillated back and forth; for an intermediate range of W, they detached and moved downstream; at relatively high W, these vortices became, once more, attached.

Experimental Validation of the Addition Principle for Pulsating Flow in Close-Coupled Catalyst Manifolds

2006 ◽  
Vol 128 (4) ◽  
pp. 656-670 ◽  
Author(s):  
Tim Persoons ◽  
Ad Hoefnagels ◽  
Eric Van den Bulck
Keyword(s):  
Experimental Validation ◽  
Engine Speed ◽  
Reverse Flow ◽  
Pulsating Flow ◽  
Exhaust Manifold ◽  
Flow Uniformity ◽  
Blow Down ◽  
Time Resolved ◽  
Flow Through ◽  
Good Agreement

Designing an exhaust manifold with close-coupled catalyst (CCC) relies heavily on time-consuming transient computional fluid dynamics. The current paper provides experimental validation of the addition principle for pulsating flow in CCC manifolds. The addition principle states that the time-averaged catalyst velocity distribution in pulsating flow equals a linear combination of velocity distributions obtained for steady flow through each of the exhaust runners. A charged motored engine flow rig provides cold pulsating flow in the exhaust manifold featuring blow down and displacement phases, typical of fired engine conditions. Oscillating hot-wire anemometry is used to measure the bidirectional velocity, with a maximum measurable negative velocity of −1m∕s. In part load and zero load conditions, instantaneous reverse flow occurs following the blow-down phase. The two-stage nature of the exhaust stroke combined with strong Helmholtz resonances results in strong fluctuations of the time-resolved mean catalyst velocity. The validity of the addition principle is quantified based on the shape and magnitude similarity between steady and pulsating flow distributions. Appropriate nondimensional groups are used to characterize the flow and quantify the similarity. Statistical significances are provided for the addition principle’s validity. The addition principle is valid when the nondimensional scavenging number S exceeds a critical value Scrit, corresponding to cases of low engine speed and/or high flow rate. This study suggests that the CCC manifold efficiency with respect to catalyst flow uniformity could be quantified using a single scalar parameter, i.e., Scrit. The results from the current study are discussed with respect to previously reported results. The combined results are in good agreement and provide a thorough statistically founded experimental validation of the addition principle, based on a broad applicability range.

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.

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