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.

scholarly journals PIV and electrodiffusion diagnostics of flow field, wall shear stress and mass transfer beneath three round submerged impinging jets

2016 ◽  
Vol 70 ◽  
pp. 417-436 ◽  
Author(s):  
Kodjovi Sodjavi ◽  
Brice Montagné ◽  
Pierre Bragança ◽  
Amina Meslem ◽  
Paul Byrne ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Impinging Jets ◽  
Wall Shear

Microscopic Velocimetry With a Scaled-Up Model for Evaluating a Flow Field Over Cultured Endothelial Cells

2002 ◽  
Vol 124 (2) ◽  
pp. 176-179 ◽  
Author(s):  
Shuichiro Fukushima ◽  
Takaaki Deguchi ◽  
Makoto Kaibara ◽  
Kotaro Oka ◽  
Kazuo Tanishita
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Cell Model ◽  
Stress Profile ◽  
Measured Velocity ◽  
Cultured Endothelial Cells ◽  
Sinusoidal Cell ◽  
Wall Shear

A microscopic velocimetry technique for evaluating the flow field over cultured endothelial cells was developed. Flow around a cell model scaled up by a factor of 100 was visualized by using an optical microscope and was quantified by using particle-tracking velocimetry. Wall shear stress on the model surface was determined from a two-dimensional velocity field interpolated from measured velocity vectors. Accuracy of the velocimetry was verified by measuring the flow over a sinusoidal cell model that had a wall shear stress profile analytically determined with linear perturbation theory. Comparison of the experimental results with the analytical solution revealed that the total error of the measured wall shear stress was 6 percent.

Measurements of Velocity and Wall Shear Stress Inside a PTFE Vascular Graft Model Under Steady Flow Conditions

1997 ◽  
Vol 119 (2) ◽  
pp. 187-194 ◽  
Author(s):  
F. Loth ◽  
S. A. Jones ◽  
D. P. Giddens ◽  
H. S. Bassiouny ◽  
S. Glagov ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Steady Flow ◽  
Axial Length ◽  
Ptfe Graft ◽  
Flow Conditions ◽  
Data Set ◽  
Stress Region ◽  
Wall Shear

The flow field inside a model of a polytetrafluoroethylene (PTFE) canine artery end-to-side bypass graft was studied under steady flow conditions using laser-Doppler anemometry. The anatomically realistic in vitro model was constructed to incorporate the major geometric features of the in vivo canine anastomosis geometry, most notably a larger graft than host artery diameter. The velocity measurements at Reynolds number 208, based on the host artery diameter, show the flow field to be three dimensional in nature. The wall shear stress distribution, computed from the near-wall velocity gradients, reveals a relatively low wall shear stress region on the wall opposite to the graft near the stagnation point approximately one artery diameter in axial length at the midplane. This low wall shear stress region extends to the sidewalls, suture lines, and along the PTFE graft where its axial length at the midplane is more than two artery diameters. The velocity distribution inside the graft model presented here provides a data set well suited for validation of numerical solutions on a model of this type.

scholarly journals Study on the Radial Sectional Velocity Distribution and Wall Shear Stress Associated With Carotid Artery Stenosis

2021 ◽  
Author(s):  
Zhiyong Song ◽  
Pengrui Zhu ◽  
Lianzhi Yang ◽  
Zhaohui Liu ◽  
Hua Li ◽  
...  
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Velocity Distribution ◽  
Carotid Artery Stenosis ◽  
Central Area ◽  
Blood Velocity ◽  
Artery Stenosis ◽  
Wall Shear

Abstract BackgroundAtherosclerosis is an important cause of cardiovascular disease. The wall shear stress (WSS) is one of the key factors of plaque formation and dislodgement. Currently, WSS estimation is based on measurement of the blood velocity gradient. However, due to the lack of flow field measurements in carotid stenosis vessels, the two distribution forms (parabolic and non-parabolic) commonly considered in numerical simulations could cause WSS estimates to differ by more than 40%, which could seriously affect the accuracy of mechanical analysis. MethodsThis study was the first to apply 3D printing technology to create an experimental model of real-structure carotid arteries. Microparticle image velocimetry (micro-PIV) was adopted to comprehensively measure blood velocity field data at the stenosis location, providing experimental validation of numerical simulation (Fluent; finite volume method) results. Then, the flow field was simulated at a normal human heart rate (45-120 beats per minute). ResultsThis study revealed that when blood flowed across the carotid artery stenosis location, the velocity distribution was not parabolic but rather a plateau-shaped distribution, with a similar flow velocity in the central area (more than 65% of the total flow path). The WSS values calculated based on a parabolic velocity distribution and the maximum velocity were nearly 60% lower.ConclusionThis study provides a reliable method for WSS determination to better understand the vascular stenosis location and facilitate flow and shear force field research. In the future, it is necessary to carry out in-depth research on the relationship between the plaque shape, flow field distribution and WSS, and amendments to the calculated WSS for clinical stenosis should be proposed.

scholarly journals Near-Wall Flow in Cerebral Aneurysms

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 89 ◽  
Author(s):  
Vahid Goodarzi Ardakani ◽  
Xin Tu ◽  
Alberto M. Gambaruto ◽  
Iolanda Velho ◽  
Jorge Tiago ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Cardiovascular System ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Normal Velocity ◽  
Wall Flow ◽  
Wall Shear ◽  
Near Wall

The region where the vascular lumen meets the surrounding endothelium cell layer, hence the interface region between haemodynamics and cell tissue, is of primary importance in the physiological functions of the cardiovascular system. The functions include mass transport to/from the blood and tissue, and signalling via mechanotransduction, which are primary functions of the cardiovascular system and abnormalities in these functions are known to affect disease formation and vascular remodelling. This region is denoted by the near-wall region in the present work, and we outline simple yet effective numerical recipes to analyse the near-wall flow field. Computational haemodynamics solutions are presented for six patient specific cerebral aneurysms, at three instances in the cardiac cycle: peak systole, end systole (taken as dicrotic notch) and end diastole. A sensitivity study, based on Newtonian and non-Newtonian rheological models, and different flow rate profiles, is effected for a selection of aneurysm cases. The near-wall flow field is described by the wall shear stress (WSS) and the divergence of wall shear stress (WSSdiv), as descriptors of tangential and normal velocity components, respectively, as well as the wall shear stress critical points. Relations between near-wall and free-stream flow fields are discussed.

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.

scholarly journals A PIV COMPARISON OF THE FLOW FIELD AND WALL SHEAR STRESS IN RIGID AND COMPLIANT MODELS OF HEALTHY CAROTID ARTERIES

2016 ◽  
Vol 17 (03) ◽  
pp. 1750041 ◽  
Author(s):  
PATRICK H. GEOGHEGAN ◽  
MARK C. JERMY ◽  
DAVID S. NOBES
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
Wall Shear Stress ◽  
Flow Field ◽  
Mechanical Response ◽  
Circulatory System ◽  
Rigid Boundary ◽  
Numerical Predictions ◽  
Wall Shear

Certain systems relevant to circulatory disease have walls which are neither rigid nor static, for example, the coronary arteries, the carotid artery and the heart chambers. In vitro modeling allows the fluid mechanics of the circulatory system to be studied without the ethical and safety issues associated with animal and human experiments. Computational methods in which the equations are coupled governing the flow and the elastic walls are maturing. Currently there is a lack of experimental data in compliant arterial systems to validate the numerical predictions. Previous experimental work has commonly used rigid wall boundaries, ignoring the effect of wall compliance. Particle Image Velocimetry is used to provide a direct comparison of both the flow field and wall shear stress (WSS) observed in experimental phantoms of rigid and compliant geometries representing an idealized common carotid artery. The input flow waveform and the mechanical response of the phantom are physiologically realistic. The results show that compliance affects the velocity profile within the artery. A rigid boundary causes severe overestimation of the peak WSS with a maximum relative difference of 61% occurring; showing compliance protects the artery from exposure to high magnitude WSS. This is important when trying to understand the development of diseases like atherosclerosis. The maximum, minimum and time averaged WSS in the rigid geometry was 2.3, 0.51 and 1.03[Formula: see text]Pa and in the compliant geometry 1.4, 0.58 and 0.84[Formula: see text]Pa, respectively.

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