scholarly journals Determination of wall shear stress from mean velocity and Reynolds shear stress profiles

2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Ralph J. Volino ◽  
Michael P. Schultz
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Reynolds Shear Stress ◽  
Mean Velocity ◽  
Stress Profiles ◽  
Wall Shear

scholarly journals FLUID FLOW AND WALL SHEAR STRESS PROFILES IN MODEL BRANCH OF ABDOMINAL AORTA

Biomechanisms ◽  
1992 ◽  
Vol 11 (0) ◽  
pp. 99-109 ◽  
Author(s):  
Takashi HIROSE ◽  
Akio TANABE ◽  
Kazuo TANISHITA
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Wall Shear Stress ◽  
Abdominal Aorta ◽  
Stress Profiles ◽  
Wall Shear

PIV Measurements in Square Backward-Facing Step

2007 ◽  
Vol 129 (8) ◽  
pp. 984-990 ◽  
Author(s):  
Mika Piirto ◽  
Aku Karvinen ◽  
Hannu Ahlstedt ◽  
Pentti Saarenrinne ◽  
Reijo Karvinen
Keyword(s):  
Shear Stress ◽  
Reynolds Stress ◽  
Reynolds Shear Stress ◽  
Experimental Tests ◽  
Expansion Ratio ◽  
Spanwise Direction ◽  
Duct Flow ◽  
Backward Facing Step ◽  
Mean Velocity ◽  
Stress Profiles

Measurements with both two-dimensional (2D) two-component and three-component stereo particle image velocimetry (PIV) and computation in 2D and three-dimensional (3D) using Reynolds stress turbulence model with commercial code are carried out in a square duct backward-facing step (BFS) in a turbulent water flow at three Reynolds numbers of about 12,000, 21,000, and 55,000 based on the step height h and the inlet streamwise maximum mean velocity U0. The reattachment locations measured at a distance of Δy=0.0322h from the wall are 5.3h, 5.6h, and 5.7h, respectively. The inlet flow condition is fully developed duct flow before the step change with the expansion ratio of 1.2. PIV results show that the mean velocity, root mean square (rms) velocity profiles, and Reynolds shear stress profiles in all the experimental flow cases are almost identical in the separated shear-layer region when they are nondimensionalized by U0. The sidewall effect of the square BFS flow is analyzed by comparing the experimental statistics with direct numerical simulation (DNS) and Reynolds stress model (RSM) data. For this purpose, the simulation is carried out for both 2D BFS and for square BFS having the same geometry in the 3D case as the experimental case at the lowest Reynolds number. A clear difference is observed in rms and Reynolds shear stress profiles between square BFS experimental results and DNS results in 2D channel in the spanwise direction. The spanwise rms velocity difference is about 30%, with experimental tests showing higher values than DNS, while in contrast, turbulence intensities in streamwise and vertical directions show slightly lower values than DNS. However, with the modeling, the turbulence statistical differences between 2D and 3D RSM cases are very modest. The square BFS indicates 0.5h–1.5h smaller reattachment distances than the reattachment lengths of 2D flow cases.

Inverse Method Used for the Determination of the Wall Shear Stress in a Sliding Rheometer Using Sandwich Probes

2010 ◽  
Author(s):  
Emna Berrich ◽  
Fethi Aloui ◽  
Jack Legrand
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Inverse Method ◽  
Mass Transfer Rate ◽  
Gap Effect ◽  
Polarization Voltage ◽  
Wall Shear ◽  
Torsional Flow

The inverse method, based on a numerical sequential estimation, has been applied for the determination of the wall shear stress of a liquid single phase flow in a sliding rheometer using multi-segment probe. This method requires the inversion of the convection diffusion equation in order to apply it to instantaneous mass transfer measurements. Polarography technique, known as the limiting diffusion current method, has been used. This requires the use of Electro-Diffusion ED probe which allows the determination of the local mass transfer rate for known flow kinematics. In addition, two-segment platinum probe was mounted flush to the inert surface of the upper disk of the sliding rheometer. Hydrodynamic oscillations have been imposed to the torsional flow (type sinusoidal), in order to study the frequency response of the sandwich probe for a fixed polarization voltage. Possible error sources which are likely to affect the interpretation of the results e.g. the directional angle effect, the inertial effect, the diffusion effect and the frequencies of oscillations effect have been studied in order to test the robustness of the inverse method within the presence of such impacts. Furthermore, to demonstrate the possible effect of non-negligible inertia and diffusion, we refer to ED results for both modified Reynolds number defined by [1] and Peclet number ranges as well as for different directional angles. An algorithm has been developed for the numerically filtering of the mass transfer signals, and therefore the wall shear stress signals. It permits to eliminate any possible noise effect due to the imposed vibrations to the torsional flow. The analysis shown that the inverse method is in a good agreement with the ED experimental results for the different cases of study, i.e. for different dimensionless Reynolds numbers, for high and low oscillation frequencies, as well as for different directional angles. The little difference is probably caused by the sensitivity of the double probe to such directional angles or to the neglecting of the insulating gap effect on the inverse method solution as a first step of the study of the inverse method for double probes signals.

scholarly journals Numerical Model for the Determination of Erythrocyte Mechanical Properties and Wall Shear Stress in vivo From Intravital Microscopy

2020 ◽  
Vol 10 ◽  
Author(s):  
Vivek P. Jani ◽  
Alfredo Lucas ◽  
Vinay P. Jani ◽  
Carlos Munoz ◽  
Alexander T. Williams ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Numerical Model ◽  
Wall Shear Stress ◽  
Intravital Microscopy ◽  
Wall Shear

Determination of arterial wall shear stress

2001 ◽  
Vol 44 (10) ◽  
pp. 1312-1321 ◽  
Author(s):  
Zhaorong Liu ◽  
Feng He ◽  
Gang Xu ◽  
Yong Chen
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Arterial Wall ◽  
Wall Shear

Supplementary Boundary-Layer Approximations for Turbulent Flow

1989 ◽  
Vol 111 (4) ◽  
pp. 420-427 ◽  
Author(s):  
L. C. Thomas ◽  
S. M. F. Hasani
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Boundary Layer Flows ◽  
Mean Velocity ◽  
Wide Range ◽  
The Mean ◽  
Wall Shear

Approximations for total stress τ and mean velocity u are developed in this paper for transpired turbulent boundary layer flows. These supplementary boundary-layer approximations are tested for a wide range of near equilibrium flows and are incorporated into an inner law method for evaluating the mean wall shear stress τ0. The testing of the proposed approximations for τ and u indicates good agreement with well-documented data for moderate rates of blowing and suction and pressure gradient. These evaluations also reveal limitations in the familiar logarithmic law that has traditionally been used in the determination of wall shear stress for non-transpired boundary-layer flows. The calculations for τ0 obtained by the inner law method developed in this paper are found to be consistent with results obtained by the modern Reynolds stress method for a broad range of near equilibrium conditions. However, the use of the proposed inner law method in evaluating the mean wall shear stress for early classic near equilibrium flow brings to question the reliability of the results for τ0 reported for adverse pressure gradient flows in the 1968 Stanford Conference Proceedings.

Near-Wall Measurements in Turbulent Boundary Layers Using Laser Doppler Anemometry

2002 ◽  
Author(s):  
T. Gunnar Johansson ◽  
Luciano Castillo
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Mean Velocity ◽  
The Mean ◽  
Wall Shear ◽  
Near Wall

Near wall measurements have been performed in a zero pressure gradient turbulent boundary layer at low to moderate local Reynolds numbers using Laser-Doppler Anemometry in order to investigate how accurately the wall shear stress can be determined. Also, scaling problems are particularly difficult at low Reynolds numbers since they involve simultaneous influences of both inner and outer scales and this is most clearly observed in the near-wall region. In order to fully describe the zero pressure gradient turbulent boundary layer at low to moderate local Reynolds numbers it is necessary to accurately measure a number of quantities. These include the mean velocity and Reynolds stresses, and their spatial derivatives all the way down to the wall (y+∼1). Integral parameters that need to be measured are the wall shear stress and boundary layer thickness, particularly the momentum thickness. Problems with the measurement of field properties get worse close to a wall, and they get worse for increasing local Reynolds number. Three different approaches to measure the wall shear stress were examined. It was found that small measurement errors in the mean velocity close to the wall significantly reduced the accuracy in determining the wall shear stress by measuring the velocity gradient at the wall. The constant stress layer was found to be affected by the advection terms. However, it was found that taking the small pressure gradient into account and improving on the spatial resolution in the outer part of the boundary layer made the momentum integral method reliable.

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