Catheter Obstruction Effect on Pulsatile Flow Rate-Pressure Drop During Coronary Angioplasty

1999 ◽  
Vol 121 (3) ◽  
pp. 281-289 ◽  
Author(s):  
R. K. Banerjee ◽  
L. H. Back ◽  
M. R. Back ◽  
Y. I. Cho
Keyword(s):  
Cardiac Cycle ◽  
Pressure Sensors ◽  
Reynolds Numbers ◽  
Phase Lag ◽  
Pressure Gradients ◽  
Catheter Obstruction ◽  
Mean Pressure ◽  
Coronary Stenoses ◽  
Basal Flow ◽  
Flow Cross

The coupling of computational hemodynamics to measured translesional mean pressure gradients with an angioplasty catheter in human coronary stenoses was evaluated. A narrowed flow cross section with the catheter present effectively introduced a tighter stenosis than the enlarged residual stenoses after balloon angioplasty; thus elevating the pressure gradient and reducing blood flow during the measurements. For resting conditions with the catheter present, flow was believed to be about 40 percent of normal basal flow in the absence of the catheter, and for hyperemia, about 20 percent of elevated flow in the patient group. The computations indicated that the velocity field was viscous dominated and quasi-steady with negligible phase lag in the Δp(t) – u¯(t) relation during the cardiac cycle at the lower hydraulic Reynolds numbers and frequency parameter. Hemodynamic interactions with smaller catheter-based pressure sensors evolving in clinical use require subsequent study since artifactually elevated translesional pressure gradients can occur during measurements with current angioplasty catheters.

Elevated Mean Translesional Pressure Gradients and Flow Limitation in Significant Human Coronary Stenoses Before Angioplasty

1999 ◽  
Author(s):  
Rupak K. Banerjee ◽  
Lloyd H. Back ◽  
Martin R. Back ◽  
Young I. Cho
Keyword(s):  
Lesion Size ◽  
Pressure Gradients ◽  
Flow Rates ◽  
Flow Reserve ◽  
Mean Pressure ◽  
Coronary Stenoses ◽  
Coronary Lesions ◽  
Limiting Values ◽  
Hyperemic Flow ◽  
Basal Flow

Abstract Blood flow was simulated in patients (Wilson et al. 1988) with physiologically significant coronary lesions (minimal lesion size dm = 0.95 mm; 68% mean diameter stenosis; measured coronary flow reserve (CFR) of 2.3) by using computational hemodynamics. Computed mean pressure gradients Δp˜ were about 9 mm Hg for basal flow, and flow limiting values about ∼ 35 mm Hg. Mean hyperemic flow rates were about 115 ml/min, and distal mean coronary pressures ∼ 55 mm Hg, a level known to cause ischemia in the subendocardium (Brown et al. 1984), and consistent with the occurrence of angina in the patients.

scholarly journals Spatial and temporal resolution of a fast-response aerodynamic pressure probe in grid-generated turbulence

2021 ◽  
Vol 62 (2) ◽  
Author(s):  
Florian M. Heckmeier ◽  
Stefan Hayböck ◽  
Christian Breitsamter
Keyword(s):  
Temporal Resolution ◽  
Pressure Sensors ◽  
Mesh Size ◽  
Reynolds Numbers ◽  
Fast Response ◽  
Pressure Probe ◽  
Aerodynamic Pressure ◽  
Kolmogorov Length Scale ◽  
High Bandwidth ◽  
Velocity Spectra

Abstract The spatial and temporal resolution of a fast-response aerodynamic pressure probe (FRAP) is investigated in a benchmark flow of grid-generated turbulence. A grid with a mesh size of $$M=6.4$$ M = 6.4 mm is tested for two different free-stream velocities, hence, resulting in Reynolds numbers of $$Re_M= \{4300,12800\}$$ R e M = { 4300 , 12800 } . A thorough analysis of the applicability of the underlying assumptions with regard to turbulence isotropy and homogeneity is carried out. Taylor’s frozen turbulence hypothesis is assumed for the calculation of deducible flow quantities, like the turbulent kinetic energy or the dissipation rate. Furthermore, besides the examination of statistical quantities, velocity spectra of measurements downstream of the grid are quantified. Results of a small fast-response five-hole pressure probe equipped with piezo-resistive differential pressure sensors are compared to single-wire hot-wire constant temperature anemometry data for two different wire lengths. Estimates of temporal and spatial turbulent scales (e.g., Taylor micro scale and Kolmogorov length scale) show good agreement to data in the literature but are affected by filtering effects. Especially in the energy spectra, very high bandwidth content cannot be resolved by the FRAP, which is mainly due to bandwidth limits in the temporal calibration of the FRAP and the minimal resolution of the integrated sensors. Graphic abstract

Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct

1967 ◽  
Vol 89 (2) ◽  
pp. 163-167 ◽  
Author(s):  
E. G. Filetti ◽  
W. M. Kays
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Duct Flow ◽  
Double Step ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Flow Cross

Experimental data are presented for local heat transfer rates near the entrance to a flat duct in which there is an abrupt symmetrical enlargement in flow cross section. Two enlargement area ratios are considered, and Reynolds numbers, based on duct hydraulic diameter, varied from 70,000 to 205,000. It is found that such a flow is characterized by a long stall on one side and a short stall on the other. Maximum heat transfer occurs in both cases at the point of reattachment, followed by a decay toward the values for fully developed duct flow. Empirical equations are given for the Nusselt number at the reattachment point, correlated as functions of duct Reynolds number and enlargement ratio.

Low-Reynolds-Number Turbulent Boundary Layers in Zero and Favorable Pressure Gradients

1983 ◽  
Vol 27 (03) ◽  
pp. 147-157 ◽  
Author(s):  
A. J. Smits ◽  
N. Matheson ◽  
P. N. Joubert
Keyword(s):  
Friction Coefficient ◽  
Skin Friction ◽  
Boundary Layers ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Skin Friction Coefficient ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Mean Flow ◽  
Low Reynolds

This paper reports the results of an extensive experimental investigation into the mean flow properties of turbulent boundary layers with momentum-thickness Reynolds numbers less than 3000. Zero pressure gradient and favorable pressure gradients were studied. The velocity profiles displayed a logarithmic region even at very low Reynolds numbers (as low as Rθ = 261). The results were independent of the leading-edge shape, and the pin-type turbulent stimulators performed well. It was found that the shape and Clauser parameters were a little higher than the correlation proposed by Coles [10], and the skin friction coefficient was a little lower. The skin friction coefficient behavior could be fitted well by a simple power-law relationship in both zero and favorable pressure gradients.

Abstract 15322: Trifecta vs. Mitroflow: Superior Hemodynamics Despite Similar Design

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Mahmoud Diab ◽  
Gloria Faerber ◽  
Ivliane Tsanava ◽  
Martin Breuer ◽  
Mario Walther ◽  
...  
Keyword(s):  
Aortic Annulus ◽  
Special Consideration ◽  
Pressure Gradients ◽  
Valve Design ◽  
Innovative Design ◽  
Mean Pressure ◽  
The Difference ◽  
Different Diameters

Purpose: Hemodynamic results of stented tissue valves are influenced by both valve design and sizing strategy. The Mitroflow and the Trifecta have an innovative design where the pericardium is wrapped around the stent. The goal of this study was to compare both valves giving special consideration to the suggested sizing strategies. Methods: We obtained pressure gradients from discharge echocardiograms from all patients having received an isolated Trifecta (n=104) or Mitroflow (n=246) between 01/2007 and 01/2014. We compared the results by size label and by the most likely selected size according to the suggested sizing strategy. This is important because the prostheses, despite having a similar design, have different diameters for the same size label and different sizing strategies. Results: The majority of implanted valves were size labels 21 and 23 (82.7% of the Trifecta and 74.8% of the Mitroflow). Mean pressure radients were lowest with Trifecta (Trifecta vs. Mitroflow, label-21: 11.4±4.65 vs 13.6±5.23 mmHg, label-23: 9.23±3.38 vs. 11.8±4.42 mmHg, p< 0.05, and label-25: 11.2±4.97 vs 12.0±4.46 mmHg, n.s.). The sizers for the Trifecta are metric, while those for the Mitroflow are 2-3 mm larger than the corresponding size label. It is therefore likely that for a patient with a 23 mm aortic annulus, a 23 Trifecta but often only a 21 Mitroflow is selected. Thus, comparing the Trifecta to the Mitroflow not by size label but by selected valve (e.g., 23 vs. 21) would therefore only increase the difference. Conclusion: The Trifecta shows a hemodynamic advantage over the Mitroflow which is not likely associated with the applied sizing strategy.

Turbulent Spots in Strong Adverse Pressure Gradients: Part 2 — Spot Propagation and Spreading Rates

2001 ◽  
Author(s):  
A. D’Ovidio ◽  
J. A. Harkins ◽  
J. P. Gostelow
Keyword(s):  
Separation Bubble ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Pressure Gradients ◽  
Flat Plates ◽  
Layer Transition ◽  
Turbulent Spots ◽  
Laminar Separation ◽  
Transition Length ◽  
Spreading Rates

The study of turbulent spots in strong adverse pressure gradients is of current interest in turbomachinery research. The aim of this investigation is to use information gathered from boundary layer transition and laminar separation, in wind tunnel tests on flat plates, to predict the equivalent phenomena occurring on turbomachinery blade surfaces. In Part 1 turbulent spot behavior was documented for two Reynolds numbers, corresponding to a laminar separation bubble (LSB) and an incipient separation condition (IS). In Part 2 further results are reported characterizing typical spot propagation and spreading rates and serving to validate or modify existing correlations for predicting transition length.

Flow Control Over a Circular Cylinder Using Pulsed DBD Actuators

2012 ◽  
Author(s):  
William C. Schneck ◽  
Walter F. O’Brien
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Gas Turbine ◽  
Electric Fields ◽  
Active Flow Control ◽  
Reynolds Numbers ◽  
Pressure Gradients ◽  
High Reynolds Numbers ◽  
Pulsed Dc ◽  
High Reynolds

Immersed bodies such as struts, vanes, and instrumentation probes in gas turbine flow systems will, except at the lowest of flow velocities, shed separated wakes. These wakes can have both upstream and downstream effects on the surrounding flow. In most applications, surrounding components are designed to be in the presence of a quasi-steady or at least non-variant flow field. The presence of unsteady wakes has both aerodynamic and structural consequences. Active flow control of wake generation can therefore be very valuable. One means to implement active flow control is by the use of plasma actuation. Plasma actuation is the use of strong electric fields to generate ionized gas that can be actuated and controlled using the electric fields. The controlling device can be based on AC, DC, or pulsed-DC actuation. The present research was conducted using pulsed-DC from a capacitive discharge power supply. The study demonstrates the applicability of, specifically, pulsed-DC plasma flow control of the flow on a circular cylinder at high Reynolds numbers. The circular cylinder was selected because its flow characteristics are related to gas turbine flowpath phenomena, and are well characterized. Further, the associated pressure gradients are some of the most severe encountered in fluid applications. The development of effective plasma actuators at high Reynolds numbers under the influence of severe pressure gradients is a necessary step toward developing useful actuators for gas turbine applications beyond laboratory use. The reported experiments were run at Reynolds numbers varying from 50,000 to 97,000, and utilizing various pulse frequencies. Further, the observed performance differences with varying electric field strengths are discussed for these Reynolds numbers. The results show that flow behaviors at high Reynolds numbers can be influenced by these types of actuators. The actuators were able to demonstrate a reduction in both wake width and momentum deficit.

scholarly journals Numerical study of pressure and velocity fluctuations in nearly isotropic turbulence

1978 ◽  
Vol 88 (4) ◽  
pp. 685-709 ◽  
Author(s):  
U. Schumann ◽  
G. S. Patterson
Keyword(s):  
Isotropic Turbulence ◽  
Initial Conditions ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Reynolds Numbers ◽  
Companion Paper ◽  
Real Space ◽  
Pressure Gradients ◽  
Velocity Statistics ◽  
Decaying Turbulence

The spectral method of Orszag & Patterson has been extended to calculate the static pressure fluctuations in incompressible homogeneous decaying turbulence at Reynolds numbers Reλ [lsim ] 35. In real space 323 points are treated. Several cases starting from different isotropic initial conditions have been studied. Some departure from isotropy exists owing to the small number of modes at small wavenumbers. Root-mean-square pressure fluctuations, pressure gradients and integral length scales have been evaluated. The results agree rather well with predictions based on velocity statistics and on the assumption of normality. The normality assumption has been tested extensively for the simulated fields and found to be approximately valid as far as fourth-order velocity correlations are concerned. In addition, a model for the dissipation tensor has been proposed. The application of the present method to the study of the return of axisymmetric turbulence to isotropy is described in the companion paper.

Probe for production and measurement of acute mitral regurgitant flow in dog

1976 ◽  
Vol 40 (2) ◽  
pp. 256-259
Author(s):  
A. G. Kleber ◽  
R. Simon ◽  
W. Rutishauser
Keyword(s):  
Mitral Valve ◽  
Left Atrial ◽  
Cardiac Cycle ◽  
Left Atrial Appendage ◽  
Left Ventricular ◽  
Small Extent ◽  
Phase Lag ◽  
Regurgitant Flow ◽  
Acute Mitral Regurgitation ◽  
Flow Through

A probe for production and measurement of acute mitral regurgitation in dogs is described. It consists of a tube that is introduced into the mitral valve through the left atrial appendage. Regurgitant flow through the tube is measured by an electromagnetic device. Variation of flow and zero flow are achieved by narrowing or occluding the tube with a rubber cuff. In animals weighing 30–50 kg, the probe does not produce significant mitral stenosis and the mitral leaflets fit closely around the probe during ventricular systole. The instantaneous relationship between mitral regurgitant flow (MRF) and the gradient between left ventricular and left atrial pressure shows a marked delay of MRF at the beginning and end of regurgitation. This delay can be attributed to some extent to electrical phase lag and to the small movement of the probe relative to the mitral valve during the cardiac cycle. Measurement of regurgitant stroke volume is affected by this movement only to a small extent.

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