Distribution of Mass Transfer Rate and Wall Shear Stress Behind Simple Rectangular Stenosis in Pulsating Flow

1989 ◽  
Vol 111 (1) ◽  
pp. 47-54 ◽  
Author(s):  
R. Yamaguchi
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Transfer Rate ◽  
Schmidt Number ◽  
Fluid Dynamic ◽  
Mass Transfer Rate ◽  
Pulsating Flow ◽  
Flow Through ◽  
Wall Shear

The distributions of mass transfer rate and wall shear stress in sinusoidal laminar pulsating flow through a two-dimensional asymmetric stenosed channel have been studied experimentally and numerically. The distributions are measured by the electrochemical method. The measurement is conducted at a Reynolds number of about 150, a Schmidt number of about 1000, a nondimensional pulsating frequency of 3.40, and a nondimensional flow amplitude of 0.3. It is suggested that the deterioration of an arterial wall distal to stenosis may be greatly enhanced by fluid dynamic effects.

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.

Design Optimization of an In Vitro Shear Stress and Mass Transfer Modifier for Endothelial Cell Culture

2009 ◽  
Author(s):  
Mark A. Van Doormaal ◽  
C. Ross Ethier
Keyword(s):  
Mass Transfer ◽  
Cell Culture ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Fluid Dynamic ◽  
Endothelial Cell Culture ◽  
Atherosclerotic Lesions ◽  
Wall Shear ◽  
Progression Of Atherosclerosis

Atherosclerosis, a disease of the large and medium arteries, is the leading cause of death in Western countries. Fluid dynamic and mass transfer phenomena are thought to play a role in the initiation and progression of atherosclerosis [1–3]. Atherosclerotic lesions are known to localize to areas such as bifurcations and curved arterial segments where shear stress and mass transfer patterns differ from those in straight arteries. However, the precise roles of wall shear stress and mass transfer in the localization of atherosclerotic lesions are not known, and this remains an active area of research. Determining the separate roles of wall shear stress and mass transfer in atherosclerosis is made more difficult because areas of abnormal wall shear stress often co-localize with areas of abnormal mass transfer.

Basal to Near Hyperemic Pulsatile Flow in a Deployed Coronary Stent

2003 ◽  
Author(s):  
Matthew D. Holcomb ◽  
Steven T. Slusher ◽  
Divakar Rajamohan ◽  
Lloyd H. Back ◽  
Milind Jog ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Fold Increase ◽  
Physiological Effects ◽  
Coronary Artery Segment ◽  
Artery Segment ◽  
Order Of Magnitude ◽  
Flow Through ◽  
Wall Shear ◽  
Hyperemic Flow

The present study focuses on developing basal to near hyperemic flow through the entrance region of a deployed stent in a coronary artery segment. Stents that are presently available in market differ significantly in design. Hence, there is a need to optimize its design such that the magnitude of wall shear stress is within physiologic limit, thus minimizing the patho-physiological effects. For near hyperemic flow, the analysis showed a 20 fold increase in the positive values of wall shear stress at the stent wires exposed to the blood flow. Further, at the void next to the entrance, the wall shear stress was an order of magnitude lower than the values typically observed in similar downstream regions.

Analysis of Flow and Wall Shear Stress in Curvature Induced Dorsal Aneurysms: Effect of Arterial Curvature

2009 ◽  
Author(s):  
Arun Ramu ◽  
Guo-Xiang Wang
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Fluid Dynamic ◽  
Cerebral Arteries ◽  
Cerebral Aneurysms ◽  
Morbidity Rate ◽  
Mortality And Morbidity ◽  
Wall Shear ◽  
Primary Velocity ◽  
The Impact

Intracranial aneurysms are abnormal enlargement in the walls of cerebral arteries. The rupture of aneurysms is the leading cause of subarachnoid hemorrhage (SAH), with a high mortality and morbidity rate. A majority of saccular cerebral aneurysms occur at sites of arterial bifurcations. However, a good percentage of aneurysms are curvature induced and are found along the cavernous arterial segment. The occurrence of such non branching aneurysms, clinically called dorsal aneurysms, can be related to the increased wall shear stress at the curved arteries. The rupture of aneurysms usually occurs at the dome region, which is subjected to reduced wall shear stress (wss) owing to low re-circulating flow. Hence it is important to understand the impact of arterial curvature on the WSS distribution along the dome of aneurysms. Previously, studies have not taken into account the aspect of low WSS along the dome region. In the present 3-d computational fluid dynamic approach, we investigate the impact of varying arterial curvature on spherical dorsal aneurysms. The primary velocity patterns, the WSS distribution along the dome of the aneurysm and the area of increased WSS have been quantified for steady flow conditions.

Spatial comparison between wall shear stress measures and porcine arterial endothelial permeability

2004 ◽  
Vol 286 (5) ◽  
pp. H1916-H1922 ◽  
Author(s):  
Heather A. Himburg ◽  
Deborah M. Grzybowski ◽  
Andrew L. Hazel ◽  
Jeffrey A. LaMack ◽  
Xue-Mei Li ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Evans Blue ◽  
Fluid Dynamic ◽  
Endothelial Permeability ◽  
Blue Dye ◽  
Evans Blue Dye ◽  
Wall Shear ◽  
And Function

A better understanding of how hemodynamic factors affect the integrity and function of the vascular endothelium is necessary to appreciate more fully how atherosclerosis is initiated and promoted. A novel technique is presented to assess the relation between fluid dynamic variables and the permeability of the endothelium to macromolecules. Fully anesthetized, domestic swine were intravenously injected with the albumin marker Evans blue dye, which was allowed to circulate for 90 min. After the animals were euthanized, silicone casts were made of the abdominal aorta and its iliac branches. Pulsatile flow calculations were subsequently made in computational regions derived from the casts. The distribution of the calculated time-dependent wall shear stress in the external iliac branches was directly compared on a point-by-point basis with the spatially varying in vivo uptake of Evans blue dye in the same arteries. The results indicate that in vivo endothelial permeability to albumin decreases with increasing time-average shear stress over the normal range. Additionally, endothelial permeability increases slightly with oscillatory shear index.

scholarly journals Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

2016 ◽  
Vol 790 ◽  
pp. 158-172 ◽  
Author(s):  
Amirhossein Arzani ◽  
Alberto M. Gambaruto ◽  
Guoning Chen ◽  
Shawn C. Shadden
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Shear Stress ◽  
Vector Field ◽  
Wall Shear Stress ◽  
Residence Time ◽  
Vessel Wall ◽  
Schmidt Number ◽  
High Schmidt Number ◽  
Near Wall

The wall shear stress (WSS) vector field provides a signature for near-wall convective transport, and can be scaled to obtain a first-order approximation of the near-wall fluid velocity. The near-wall flow field governs mass transfer problems in convection-dominated open flows with high Schmidt number, in which case a flux at the wall will lead to a thin concentration boundary layer. Such near-wall transport is of particular interest in cardiovascular flows whereby haemodynamics can initiate and progress biological events at the vessel wall. In this study we consider mass transfer processes in pulsatile blood flow of abdominal aortic aneurysms resulting from complex WSS patterns. Specifically, the Lagrangian surface transport of a species released at the vessel wall was advected in forward and backward time based on the near-wall velocity field. Exposure time and residence time measures were defined to quantify accumulation of trajectories, as well as the time required to escape the near-wall domain. The effect of diffusion and normal velocity was investigated. The trajectories induced by the WSS vector field were observed to form attracting and repelling coherent structures that delineated species distribution inside the boundary layer consistent with exposure and residence time measures. The results indicate that Lagrangian WSS structures can provide a template for near-wall transport.

scholarly journals Identification of the haemodynamic environment permissive for plaque erosion

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michael McElroy ◽  
Yongcheol Kim ◽  
Giampaolo Niccoli ◽  
Rocco Vergallo ◽  
Alexander Langford-Smith ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Fluid Dynamic ◽  
Stress Gradient ◽  
Plaque Erosion ◽  
Reference Segment ◽  
Stress Maximum ◽  
Relative Residence Time ◽  
Coronary Syndromes ◽  
Wall Shear

AbstractEndothelial erosion of atherosclerotic plaques is the underlying cause of approximately 30% of acute coronary syndromes (ACS). As the vascular endothelium is profoundly affected by the haemodynamic environment to which it is exposed, we employed computational fluid dynamic (CFD) analysis of the luminal geometry from 17 patients with optical coherence tomography (OCT)-defined plaque erosion, to determine the flow environment permissive for plaque erosion. Our results demonstrate that 15 of the 17 cases analysed occurred on stenotic plaques with median 31% diameter stenosis (interquartile range 28–52%), where all but one of the adherent thrombi located proximal to, or within the region of maximum stenosis. Consequently, all flow metrics related to elevated flow were significantly increased (time averaged wall shear stress, maximum wall shear stress, time averaged wall shear stress gradient) with a reduction in relative residence time, compared to a non-diseased reference segment. We also identified two cases that did not exhibit an elevation of flow, but occurred in a region exposed to elevated oscillatory flow. Our study demonstrates that the majority of OCT-defined erosions occur where the endothelium is exposed to elevated flow, a haemodynamic environment known to evoke a distinctive phenotypic response in endothelial cells.

Sign in / Sign up

Export Citation Format

Share Document