Wall-Shear Stress Assessment in Zero-Pressure Gradient Turbulent Flow using MPS

2008 ◽  
pp. 97-99
Author(s):  
S. Groβe ◽  
W. Schröder
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flow ◽  
Pressure Gradient ◽  
Stress Assessment ◽  
Wall Shear

scholarly journals Reproducibility of wall shear stress assessment with the paraboloid method in the internal carotid artery with velocity encoded MRI in healthy young individuals

2007 ◽  
Vol 26 (3) ◽  
pp. 598-605 ◽  
Author(s):  
Frieke M.A. Box ◽  
Rob J. van der Geest ◽  
Jeroen van der Grond ◽  
Matthias J.P. van Osch ◽  
Aeilko H. Zwinderman ◽  
...  
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
Wall Shear Stress ◽  
Internal Carotid Artery ◽  
Internal Carotid ◽  
Stress Assessment ◽  
Wall Shear

A Superposition Analysis of the Turbulent Boundary Layer in an Adverse Pressure Gradient

1951 ◽  
Vol 18 (1) ◽  
pp. 95-100
Author(s):  
Donald Ross ◽  
J. M. Robertson
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Pressure Recovery ◽  
Stress Coefficient ◽  
Wall Shear

Abstract As an interim solution to the problem of the turbulent boundary layer in an adverse pressure gradient, a super-position method of analysis has been developed. In this method, the velocity profile is considered to be the result of two effects: the wall shear stress and the pressure recovery. These are superimposed, yielding an expression for the velocity profiles which approximate measured distributions. The theory also leads to a more reasonable expression for the wall shear-stress coefficient.

Roughness Influence on Turbulent Flow Through Annular Seals

1994 ◽  
Vol 116 (2) ◽  
pp. 321-328 ◽  
Author(s):  
Victor Lucas ◽  
Sterian Danaila ◽  
Olivier Bonneau ◽  
Jean Freˆne
Keyword(s):  
Surface Roughness ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flow ◽  
Dynamic Characteristics ◽  
Reynolds Equation ◽  
Mixing Length ◽  
Local Shear ◽  
Wall Shear ◽  
Local Shear Stress

This paper deals with an analysis of turbulent flow in annular seals with rough surfaces. In this approach, our objectives are to develop a model of turbulence including surface roughness and to quantify the influence of surface roughness on turbulent flow. In this paper, in order to simplify the analysis, the inertial effects are neglected. These effects will be taken into account in a subsequent work. Consequently, this study is based on the solution of Reynolds equation. Turbulent flow is solved using Prandtl’s turbulent model with Van Driest’s mixing length expression. In Van Driest’s model, the mixing length depends on wall shear stress. However there are many numerical problems in evaluating this wall shear stress. Therefore, the goal of this work has been to use the local shear stress in the Van Driest’s model. This derived from the work of Elrod and Ng concerning Reichardt’s mixing length. The mixing length expression is then modified to introduce roughness effects. Then, the momentum equations are solved to evaluate the circumferential and axial velocity distributions as well as the turbulent viscosity μ1 (Boussinesq’s hypothesis) within the film. The coefficients of turbulence kx and kz, occurring in the generalized Reynolds’ equation, are then calculated as functions of the flow parameters. Reynolds’ equation is solved by using a finite centered difference method. Dynamic characteristics are calculated by exciting the system numerically, with displacement and velocity perturbations. The model of Van Driest using local shear stress and function of roughness has been compared (for smooth seals) to the Elrod and Ng theory. Some numerical results of the static and dynamic characteristics of a rough seal (with the same roughness on the rotor as on the stator) are presented. These results show the influence of roughness on the dynamic behavior of the shaft.

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

scholarly journals Biorheological Model on Flow of Herschel-Bulkley Fluid through a Tapered Arterial Stenosis with Dilatation

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
S. Priyadharshini ◽  
R. Ponalagusamy
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Power Law ◽  
Flow Resistance ◽  
Velocity Profiles ◽  
Arterial Stenosis ◽  
Axial Distance ◽  
Tapered Artery ◽  
Wall Shear

An analysis of blood flow through a tapered artery with stenosis and dilatation has been carried out where the blood is treated as incompressible Herschel-Bulkley fluid. A comparison between numerical values and analytical values of pressure gradient at the midpoint of stenotic region shows that the analytical expression for pressure gradient works well for the values of yield stress till 2.4. The wall shear stress and flow resistance increase significantly with axial distance and the increase is more in the case of converging tapered artery. A comparison study of velocity profiles, wall shear stress, and flow resistance for Newtonian, power law, Bingham-plastic, and Herschel-Bulkley fluids shows that the variation is greater for Herschel-Bulkley fluid than the other fluids. The obtained velocity profiles have been compared with the experimental data and it is observed that blood behaves like a Herschel-Bulkley fluid rather than power law, Bingham, and Newtonian fluids. It is observed that, in the case of a tapered stenosed tube, the streamline pattern follows a convex pattern when we move fromr/R=0tor/R=1and it follows a concave pattern when we move fromr/R=0tor/R=-1. Further, it is of opposite behaviour in the case of a tapered dilatation tube which forms new information that is, for the first time, added to the literature.

scholarly journals Modeling Blood Pulsatile Turbulent Flow in Stenotic Coronary Arteries

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flow ◽  
Newtonian Fluid ◽  
Coronary Arteries ◽  
Pathological Condition ◽  
Flow Behavior ◽  
Wall Shear ◽  
Stenotic Arteries

Atherosclerosis is a potentially serious illness where arteries become clogged with fatty substances called plaques. Over the years, this pathological condition has been deeply studied and computational fluid dynamics has played an important role in investigating the blood flow behavior. Commonly, the blood flow is assumed to be laminar and a Newtonian fluid. However, under a stenotic condition, the blood behaves as a non-Newtonian fluid and the pulsatile blood flow through coronary arteries could result in a transition from laminar to turbulent flow condition. The present study aims to analyze and compare numerically the blood flow behavior, applying the k-ω SST model and a laminar assumption. The effects of Newtonian and non-Newtonian (Carreau) models were also studied. In addition, the effect of the stenosis degree on velocity fields and wall shear stress based descriptors were evaluated. According to the results, the turbulent model is shown to give a better overall representation of pulsatile flow in stenotic arteries. Regarding, the effect of non-Newtonian modeling, it was found to be more significant in wall shear stress measurements than in velocity profiles. In addition, the appearance of recirculation zones in the 50% stenotic model was observed during systole, and a low TAWSS and high OSI were detected downstream of the stenosis which, in turn, are risk factors for plaque formation. Finally, the turbulence intensity measurements allowed to distinguish regions of recirculating and disturbed flow.

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