Experimental Measurements of the Flow-Induced Shear Stress Distribution in the Vicinity of Prosthetic Heart Valves

1981 ◽  
Vol 103 (4) ◽  
pp. 267-274 ◽  
Author(s):  
W. H. Herkes ◽  
J. R. Lloyd
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Test Section ◽  
Heart Valves ◽  
Reynolds Numbers ◽  
Shear Stress Distribution ◽  
Electrochemical Technique ◽  
Prosthetic Heart Valves ◽  
Disk Valve ◽  
Flow Through

The present study examines the local shear stress distribution occurring during flow through prosthetic valves. The electrochemical technique is a powerful tool for the study of mass transfer related phenomena and was selected for this investigation. The present investigation attempts to establish the viability of the particular application of the technique. Three test section geometries were analyzed: a straight tube, a ball-in-cage valve, and a model disk-in-cage valve, and the tests were conducted at six Reynolds numbers ranging from 1000 to 6000 under steady-state conditions. The model disk valve provided a base-case check on the validity of the technique since it has been employed in several previous studies and the flow through it is well documented. High shear and low shear regions are clearly evident and their locations can be pinpointed. The ball-in-cage valve was tested over the full range of Reynolds numbers. The shear profiles demonstrate a double peak in the region of the ball, a result which was unexpected. Careful study revealed that this was a result of the test section geometry and provides another demonstration of the importance of test section geometry. The frequency of the fluctuations in wall shear for the ball valve were found to be different than those for the disk valve indicating that the environment at the aortic wall is definitely affected by valve design. This study showed the electrochemical technique to be a valuable tool for the study of the flow through prosthetic heart valves.

Annular Two-Phase Flow—Part 2: Additional Effects

1970 ◽  
Vol 92 (1) ◽  
pp. 73-81 ◽  
Author(s):  
G. B. Wallis
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Liquid Film ◽  
Relative Velocity ◽  
Two Phase Flow ◽  
Reynolds Numbers ◽  
Shear Stress Distribution ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Part

The theory of Part 1 is modified by taking additional phenomena into account. The liquid film, the gas core, and the interface are considered separately. The effects of entrainment, compressibility, liquid and gas Reynolds numbers, shear-stress distribution, relative velocity, and the various types of interfacial waves are discussed.

An Experimental Study of the Flow-Induced Mass Transfer Distribution in the Vicinity of Prosthetic Heart Valves

1981 ◽  
Vol 103 (1) ◽  
pp. 1-10 ◽  
Author(s):  
F. L. Galanga ◽  
J. R. Lloyd
Keyword(s):  
Mass Transfer ◽  
Experimental Study ◽  
Heart Valves ◽  
Electrochemical Techniques ◽  
Reynolds Numbers ◽  
In Vivo Studies ◽  
High Mass ◽  
Prosthetic Heart Valves ◽  
Disk Valve

An experimental study of the flow-induced mass transfer distribution in the vicinity of a model disk valve and a ball valve was conducted using electrochemical techniques. Reynolds numbers ranged from 1000 to 6000, which are characteristic of physiologic conditions. Local instantaneous and time average data are presented. It was found that the flow-induced mass transfer distribution was high in regions of both low and high shear. It was also demonstrated that the fluctuations in the mass transfer to the wall of the test section around the valve are significantly affected by valve design. The regions of high mass transfer measured in this study were found to correlate very closely to regions where thrombus formations have been documented in in-vivo studies.

scholarly journals Assessing Machine Learning versus a Mathematical Model to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 596
Author(s):  
Babak Lashkar-Ara ◽  
Niloofar Kalantari ◽  
Zohreh Sheikh Khozani ◽  
Amir Mosavi
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Fuzzy Inference ◽  
Rectangular Channel ◽  
Tsallis Entropy ◽  
Shear Stress Distribution ◽  
Data Series ◽  
Shear Stresses ◽  
Inference System ◽  
Aspect Ratios

One of the most important subjects of hydraulic engineering is the reliable estimation of the transverse distribution in the rectangular channel of bed and wall shear stresses. This study makes use of the Tsallis entropy, genetic programming (GP) and adaptive neuro-fuzzy inference system (ANFIS) methods to assess the shear stress distribution (SSD) in the rectangular channel. To evaluate the results of the Tsallis entropy, GP and ANFIS models, laboratory observations were used in which shear stress was measured using an optimized Preston tube. This is then used to measure the SSD in various aspect ratios in the rectangular channel. To investigate the shear stress percentage, 10 data series with a total of 112 different data for were used. The results of the sensitivity analysis show that the most influential parameter for the SSD in smooth rectangular channel is the dimensionless parameter B/H, Where the transverse coordinate is B, and the flow depth is H. With the parameters (b/B), (B/H) for the bed and (z/H), (B/H) for the wall as inputs, the modeling of the GP was better than the other one. Based on the analysis, it can be concluded that the use of GP and ANFIS algorithms is more effective in estimating shear stress in smooth rectangular channels than the Tsallis entropy-based equations.

scholarly journals Wall Shear Stress Distribution of Small Aneurysms Prone to Rupture

Stroke ◽  
2014 ◽  
Vol 45 (1) ◽  
pp. 261-264 ◽  
Author(s):  
Vitor Mendes Pereira ◽  
Olivier Brina ◽  
Philippe Bijlenga ◽  
Pierre Bouillot ◽  
Ana Paula Narata ◽  
...  
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Wall Shear Stress ◽  
Shear Stress Distribution ◽  
Wall Shear Stress Distribution ◽  
Wall Shear ◽  
Small Aneurysms
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