Phasic and Spatial Pressure Measurements in a Femoral Artery Branch Model for Pulsatile Flow

1986 ◽  
Vol 108 (3) ◽  
pp. 251-258 ◽  
Author(s):  
L. H. Back ◽  
Y. I. Cho ◽  
D. W. Crawford
Keyword(s):  
Femoral Artery ◽  
Large Range ◽  
Reynolds Numbers ◽  
Wave Form ◽  
Pressure Gradients ◽  
Pressure Losses ◽  
Pressure Distributions ◽  
Branch Model ◽  
Flow Resistances ◽  
Artery Branch

Phasic and spatial time-averaged pressure distributions were measured in a 60-deg femoral artery branch model over a large range of branch flow ratios and at physiological Reynolds numbers of about 120 and 700. The results obtained with an in-vivolike flow wave form indicated spatial adverse time average pressure gradients in the branch vicinity which increased in magnitude with branch flow ratio, and the importance of the larger inertial effects at the higher Reynolds numbers. Pressure losses in the branch entrance region were relatively large, and corresponding flow resistances may limit branch flow, particularly at higher Reynolds numbers. The effect of branch flow was to reduce the pressure loss in the main lumen.

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.

Measurements of Resistance of Individual Square-Mesh Screens to Oscillating Flow at Low and Intermediate Reynolds Numbers

2003 ◽  
Vol 125 (5) ◽  
pp. 851-862 ◽  
Author(s):  
Ray Scott Wakeland ◽  
Robert M. Keolian
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Steady Flow ◽  
Oscillation Amplitude ◽  
Low Frequency ◽  
Reynolds Numbers ◽  
Oscillating Flow ◽  
Pressure Losses ◽  
Approach Velocity ◽  
Flow Resistances

Measurements are reported of pressure losses across single screens subjected to low-frequency oscillating flow for 0.002≲Red≲400, where Red is Reynolds number based on wire diameter and peak approach velocity. Several correlation methods are examined. Extensive comparisons are made between present oscillating-flow results and previous reports of the resistance of screens to steady flow. Defining oscillating results in terms of peak amplitudes, the oscillating and steady-flow resistances are found to be the same, including behavior in the intermediate Reynolds number region that departs from correlations of the form ARe−1+B. The friction factor is also found to depend on Reynolds number, but not independently on oscillation amplitude, over the range of conditions measured.

The Influence of Reynolds Number and Row Position on Surface Pressure Distributions in Staggered Pin Fin Arrays

2006 ◽  
Author(s):  
F. E. Ames ◽  
L. A. Dvorak
Keyword(s):  
Reynolds Number ◽  
Surface Pressure ◽  
Measurement Techniques ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Pressure Gradients ◽  
Stagnation Region ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Pin Fin Array

Full surface pressure distributions over the endwall and pin in a staggered pin fin array have been acquired over a ten to one range in Reynolds numbers. These pressure distributions allow us to visualize the strong inertial pressure gradients that are responsible for driving secondary flows in pin fin passages. These strong pressure gradients include endwall regions near the pin stagnation region and near the pin at 90° from the stagnation region. Pressure distributions have been acquired on pin and endwall surfaces at eight consecutive rows using conventional static pressure measurement techniques. Pressures have been taken at 380 locations per row and, assuming symmetry, provide a well resolved visualization of surface pressure. Generally, surface and pin pressure distributions vary significantly from row to row in the entrance of the array at a given Reynolds number but stay relatively consistent after row four. Dimensionless pressure distributions are quite similar for row one for all Reynolds numbers but vary significantly at a given row downstream with Reynolds number. These data are expected to enhance our understanding of pin array fluid dynamics and to compliment full surface heat transfer data presented in a future paper.

Influence of Loading Distribution on the Performance of Transonic HP Turbine Blades

2003 ◽  
Author(s):  
D. Corriveau ◽  
S. A. Sjolander
Keyword(s):  
Turbine Blade ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Blade Loading ◽  
Pressure Losses ◽  
Pressure Distributions ◽  
Mach Numbers ◽  
Exit Mach Number ◽  
Transonic Wind Tunnel ◽  
Made In

Midspan measurements were made in a transonic wind tunnel for three HP turbine blade cascades at design incidence. The baseline profile is the midspan section of a HP turbine blade of fairly recent design. It is considered mid-loaded. To gain a better understanding of blade loading limits and the influence of loading distributions, the profile of the baseline airfoil was modified to create two new airfoils having aft-loaded and front-loaded pressure distributions. Tests were performed for exit Mach numbers between 0.6 and 1.2. In addition, measurements were made for an extended range of Reynolds numbers for constant Mach numbers of 0.6, 0.85, 0.95 and 1.05. At the design exit Mach number of 1.05, the aft-loaded airfoil showed a reduction of almost 20% in the total pressure losses compared with the baseline airfoil. However, it was also found that for Mach numbers higher than the design value the performance of the aft-loaded blade deteriorated rapidly. The front-loaded airfoil showed generally inferior performance compared with the baseline airfoil.

scholarly journals Validation of a CFD Methodology for Variable Speed Power Turbine Relevant Conditions

2013 ◽  
Author(s):  
Ali A. Ameri ◽  
Paul W. Giel ◽  
Ashlie B. McVetta
Keyword(s):  
Three Dimensional ◽  
Reynolds Numbers ◽  
Transitional Flow ◽  
Variable Speed ◽  
Low Reynolds Numbers ◽  
Pressure Losses ◽  
Pressure Distributions ◽  
Power Turbine ◽  
Wide Range ◽  
Transfer Problems

Analysis tools are needed to investigate aerodynamic performance of Variable-Speed Power Turbines (VSPT) for rotorcraft applications. The VSPT operates at low Reynolds numbers (transitional flow) and over a wide range of incidence. Previously, the capabilities of a published three-equation transition and turbulence model in predicting the transition location for three-dimensional heat transfer problems were assessed. In this paper, results are presented of a post-diction exercise using a three-dimensional flow in a transonic linear cascade comprising VSPT blading. The measured pressure distributions and integrated spanwise total pressure losses and flow angles for two incidence angles corresponding to cruise (i = +5.8°) and takeoff (i = –36.7°) were used for this study. For the higher loading condition of cruise and the negative incidence condition of takeoff, overall agreement with data may be considered satisfactory but areas of needed improvement are also indicated.

Influence of Loading Distribution on the Performance of Transonic High Pressure Turbine Blades

2004 ◽  
Vol 126 (2) ◽  
pp. 288-296 ◽  
Author(s):  
D. Corriveau ◽  
S. A. Sjolander
Keyword(s):  
High Pressure ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
High Pressure Turbine ◽  
Blade Loading ◽  
Pressure Losses ◽  
Pressure Distributions ◽  
Mach Numbers ◽  
Exit Mach Number

Midspan measurements were made in a transonic wind tunnel for three high pressure turbine blade cascades at design incidence. The baseline profile is the midspan section of a high pressure turbine blade of fairly recent design. It is considered mid-loaded. To gain a better understanding of blade loading limits and the influence of loading distributions, the profile of the baseline airfoil was modified to create two new airfoils having aft-loaded and front-loaded pressure distributions. Tests were performed for exit Mach numbers between 0.6 and 1.2. In addition, measurements were made for an extended range of Reynolds numbers for constant Mach numbers of 0.6, 0.85, 0.95, and 1.05. At the design exit Mach number of 1.05, the aft-loaded airfoil showed a reduction of almost 20% in the total pressure losses compared with the baseline airfoil. However, it was also found that for Mach numbers higher than the design value the performance of the aft-loaded blade deteriorated rapidly. The front-loaded airfoil showed generally inferior performance compared with the baseline airfoil.

The Influence of Element Thermal Conductivity, Shape, and Density on Heat Transfer in a Rough Wall Turbulent Boundary Layer With Strong Pressure Gradients

2021 ◽  
Vol 143 (8) ◽  
Author(s):  
Christoph Gramespacher ◽  
Holger Albiez ◽  
Matthias Stripf ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Reynolds Numbers ◽  
Formation Mechanisms ◽  
Pressure Gradients ◽  
Pressure Distributions ◽  
Roughness Elements ◽  
The Difference ◽  
Study Heat Transfer

Abstract Formation mechanisms for turbine roughness are manifold, including erosion, corrosion, deposition, and spallation or more recently additive manufacturing processes. Consequently, the resulting surfaces differ remarkably not only in roughness shape, height, and density but also in element thermal conductivity. Because the roughness elements extend into the boundary layer, their temperature distribution has a direct influence on the thermal boundary layer and thus on the resulting convective heat transfer. In the current study, heat transfer distributions along a flat plate with more than 20 deterministic rough surface topographies that differ in element eccentricity, height and density are measured. For each surface roughness, measurements are conducted using two different element thermal conductivities (0.2 W/(mK) and 30 W/(mK)), two pressure distributions, four Reynolds numbers between 3 × 105 and 7.5 × 105 and various inlet turbulence intensities in the range of 1.5 % to 8 %. The pressure distributions resemble a typical suction and pressure side, respectively. Results show a heat transfer increase of up to 60 % for the high thermal conductivity surfaces and up to 50 % for the low conductivity ones. While heat transfer on the high conductivity surfaces is always higher than on the low conductivity ones, the difference becomes smaller with decreasing element density.

The Influence of Element Thermal Conductivity, Shape, and Density on Heat Transfer in a Rough Wall Turbulent Boundary Layer With Strong Pressure Gradients

2020 ◽  
Author(s):  
Christoph Gramespacher ◽  
Holger Albiez ◽  
Mattias Stripf ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Reynolds Numbers ◽  
Formation Mechanisms ◽  
Pressure Gradients ◽  
Pressure Distributions ◽  
Roughness Elements ◽  
The Difference ◽  
Study Heat Transfer

Abstract Formation mechanisms for turbine roughness are manifold, including erosion, corrosion, deposition, and spallation or more recently additive manufacturing processes. Consequently, the resulting surfaces differ remarkably not only in roughness shape, height, and density, but also in element thermal conductivity. Because the roughness elements extend into the boundary layer, their temperature distribution has a direct influence on the thermal boundary layer and thus on the resulting convective heat transfer. In the current study, heat transfer distributions along a flat plate with more than 20 deterministic rough surface topographies that differ in element eccentricity, height and density are measured. For each surface roughness, measurements are conducted using two different element thermal conductivities (0.2 W/(mK) and 30 W/(mK)), two pressure distributions, four Reynolds numbers between 3 × 105 and 7.5 × 105 and various inlet turbulence intensities in the range of 1.5% to 8%. The pressure distributions resemble a typical suction and pressure side, respectively. Results show a heat transfer increase of up to 60% for the high thermal conductivity surfaces and up to 50% for the low conductivity ones. While heat transfer on the high conductivity surfaces is always higher than on the low conductivity ones, the difference becomes smaller with decreasing element density.

scholarly journals Turbulence model performance for ventilation components pressure losses

2021 ◽  
Author(s):  
Karsten Tawackolian ◽  
Martin Kriegel
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Test Case ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Near Wall

AbstractThis study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

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.

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