Wall Shear Stress Measurements on a Highly Loaded Compressor Cascade

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Vincent Zander ◽  
Christoph Dobriloff ◽  
Mathias Lumpe ◽  
Wolfgang Nitsche
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Flow Direction ◽  
Flow Structures ◽  
Full Potential ◽  
Compressor Cascade ◽  
Stress Measurements ◽  
Wall Shear ◽  
Highly Loaded

This paper presents wall shear stress measurements obtained with a new type of wall-mounted probe based on the thermal electrical principle. The sensor consists of three single surface hot wires arranged in a δ configuration. This allows for measuring wall shear stress magnitude and direction simultaneously. Each probe has to be calibrated in a flat plate experiment for a number of wall shear values and flow directions before applying it to the relevant flow situation. To assess the full potential of the newly designed sensors, they were applied to a low-speed, large-scale cascade test section equipped with highly loaded compressor blades. The high blade loading in conjunction with a small blade aspect ratio results in a strongly three-dimensional flow field with large secondary flow structures and flow separation. Furthermore, laminar separation bubbles can be observed on the blade surface. The wall shear stress distribution allows for resolving these existing flow structures and provides detailed insight into the flow on the blade’s surface. The additionally measured flow direction reveals further details of the flow field. Parallel to the experiments, RANS simulations were conducted using the commercial flow solver CFX to compare the simulated results with the measured values.

Wall Shear Stress Measurements on a Highly Loaded Compressor Cascade

2011 ◽  
Author(s):  
Vincent Zander ◽  
Christoph Dobriloff ◽  
Mathias Lumpe ◽  
Wolfgang Nitsche
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Flow Direction ◽  
Flow Structures ◽  
Full Potential ◽  
Compressor Cascade ◽  
Stress Measurements ◽  
Wall Shear ◽  
Highly Loaded

This paper presents wall shear stress measurements obtained with a new type of wall-mounted probe based on the thermal electrical principle. The sensor consists of three single surface hot wires arranged in a delta configuration. This allows for measuring wall shear stress magnitude and direction simultaneously. Each probe has to be calibrated in a flat plate experiment for a number of wall shear values and flow directions before applying it to the relevant flow situation. To assess the full potential of the newly designed sensors, they were applied to a low speed, large scale cascade test section equipped with highly loaded compressor blades. The high blade loading in conjunction with a small blade aspect ratio results in a strongly three-dimensional flow field with large secondary flow structures and flow separation. Furthermore, laminar separation bubbles can be observed on the blade surface. The wall shear stress distribution allows for resolving these existing flow structures and provides detailed insight into the flow on the blade’s surface. The additionally measured flow direction reveals further details of the flow field. Parallel to the experiments, RANS simulations were conducted using the commercial flow solver CFX to compare the simulated results with the measured values.

Exploring wall shear stress spatiotemporal heterogeneity in coronary arteries combining correlation-based analysis and complex networks with computational hemodynamics

2020 ◽  
Vol 234 (11) ◽  
pp. 1209-1222 ◽  
Author(s):  
Karol Calò ◽  
Giuseppe De Nisco ◽  
Diego Gallo ◽  
Claudio Chiastra ◽  
Ayla Hoogendoorn ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Complex Networks ◽  
Coronary Arteries ◽  
Early Stage ◽  
Flow Direction ◽  
Computational Hemodynamics ◽  
Time Histories ◽  
Wall Shear

Atherosclerosis at the early stage in coronary arteries has been associated with low cycle-average wall shear stress magnitude. However, parallel to the identification of an established active role for low wall shear stress in the onset/progression of the atherosclerotic disease, a weak association between lesions localization and low/oscillatory wall shear stress has been observed. In the attempt to fully identify the wall shear stress phenotype triggering early atherosclerosis in coronary arteries, this exploratory study aims at enriching the characterization of wall shear stress emerging features combining correlation-based analysis and complex networks theory with computational hemodynamics. The final goal is the characterization of the spatiotemporal and topological heterogeneity of wall shear stress waveforms along the cardiac cycle. In detail, here time-histories of wall shear stress magnitude and wall shear stress projection along the main flow direction and orthogonal to it (a measure of wall shear stress multidirectionality) are analyzed in a representative dataset of 10 left anterior descending pig coronary artery computational hemodynamics models. Among the main findings, we report that the proposed analysis quantitatively demonstrates that the model-specific inlet flow-rate shapes wall shear stress time-histories. Moreover, it emerges that a combined effect of low wall shear stress magnitude and of the shape of the wall shear stress–based descriptors time-histories could trigger atherosclerosis at its earliest stage. The findings of this work suggest for new experiments to provide a clearer determination of the wall shear stress phenotype which is at the basis of the so-called arterial hemodynamic risk hypothesis in coronary arteries.

Wall Shear Stress Measurements

2015 ◽  
pp. 3479-3486 ◽  
Author(s):  
Christian Cierpka ◽  
Massimiliano Rossi ◽  
Christian J. Kähler
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Stress Measurements ◽  
Wall Shear

Fluctuating Shear Stress Calibration Method Using a Channel Flow

2010 ◽  
Author(s):  
Daniel C. Cole ◽  
Michael L. Jonson ◽  
Kendra V. Sharp
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Calibration Method ◽  
Direct Shear ◽  
Radiated Noise ◽  
Calibration Device ◽  
Wall Shear ◽  
Oscillating Plate ◽  
Temporal Field

Fluctuating wall shear stress causes vibration and radiated noise from a structure. In the past wall shear stress has been measured indirectly using hot wires and hot films. Recently direct shear sensors have been developed. In this paper a calibration device consisting of a 305 mm × 60 mm × 5 mm channel filled with glycerin is used to calibrate a direct shear stress sensor with amplitudes up to 10 Pa of shear stress over a frequency range from 10 Hz to 1 kHz. The analytically known flow field caused by an oscillating plate 5 mm from the sensor is verified using laser Doppler velocimetry (LDV). The flow field is derived using a frequency-wavenumber approach thereby allowing for a known spatial and temporal field to be generated by specifying a derived plate vibration.

Effects of Steady Spatial Wall Shear Stress Gradients on Endothelial Cell Morphology in Three-Dimensional Models

2007 ◽  
Author(s):  
Leonie Rouleau ◽  
Monica Farcas ◽  
Jean-Claude Tardif ◽  
Rosaire Mongrain ◽  
Richard Leask
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Endothelial Cell ◽  
Wall Shear Stress ◽  
Cell Morphology ◽  
Flow Direction ◽  
Stress Gradient ◽  
Spatial Gradient ◽  
Stress Gradients ◽  
Wall Shear

Endothelial cell (EC) dysfunction has been linked to atherosclerosis through their response to hemodynamic forces. Flow in stenotic vessels creates complex spatial gradients in wall shear stress. In vitro studies examining the effect of shear stress on endothelial cells have used unrealistic and simplified models, which cannot reproduce physiological conditions. The objective of this study was to expose endothelial cells to the complex shear shear pattern created by an asymmetric stenosis. Endothelial cells were grown and exposed for different times to physiological steady flow in straight dynamic controls and in idealized asymmetric stenosis models. Cells subjected to 1D flow aligned with flow direction and had a spindle-like shape when compared to static controls. Endothelial cell morphology was noticeable different in the regions with a spatial gradient in wall shear stress, being more randomly oriented and of cobblestone shape. This occurred despite the presence of an increased magnitude in shear stress. No other study to date has described this morphology in the presence of a positive wall shear stress gradient or gradient of significant shear magnitude. This technique provides a more realistic model to study endothelial cell response to spatial and temporal shear stress gradients that are present in vivo and is an important advancement towards a better understanding of the mechanisms involved in coronary artery disease.

MR-based wall shear stress measurements in fully developed turbulent flow using the Clauser plot method

2019 ◽  
Vol 305 ◽  
pp. 16-21
Author(s):  
Nina Shokina ◽  
Andreas Bauer ◽  
Gabriel Teschner ◽  
Waltraud B. Buchenberg ◽  
Cameron Tropea ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flow ◽  
Stress Measurements ◽  
Fully Developed Turbulent Flow ◽  
Wall Shear
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