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Prediction of vortex structures in pulsatile flow through S-bend arterial geometry with different stenosis levels

Khan Piru Mohan, Raj Apurva, Alam Md. Irshad, Chakraborty Suman, Roy Somnath

Biocybernetics and Biomedical Engineering

2023

Vol. 43, no. 1

298--312

Arterial stenosis poses a high cardiovascular risk, and clinical intervention is needed when these stenoses grow beyond a specific limit. The study of vortex dynamics in these diseased arteries can be beneficial to understand its severity. Therefore, in the present work, we have investigated the flow structures in an S-bend arterial geometry with different levels of stenosis using a sharp interface immersed boundary method. We have observed an onset of Kelvin-Helmholtz-type vortex roll-up for higher degrees of stenoses. Fluctuations in the wall shear stress are observed for higher stenosis degrees. However, these fluctuations depend on the position and length of the stenosis. Newtonian and non-Newtonian Carreau fluids predict similar vortex structures, although minor differences in the Kelvin-Helmholtz vortex structures and associated fluctuations are observed in the diastolic phase. The Newtonian fluid predicts a slightly longer low time-averaged wall shear stress (≤0.5 Pa) region immediately after the stenosis compared with the Carreau fluid in the 58 % blockage S-bend artery.

The vortex dynamics in HTc superconductor in external magnetic field

Sosnowski J.

Journal of Technical Physics

2005

Vol. 46, no 4

245-255

The penetration of magnetic induction into HTc superconductors has been considered taking into account the layered structure of these materials. For magnetic field parallel to the planes a one-dimensional penetration has been considered, while in perpendicular magnetic field it is a two-dimensional problem. The flux creep equation has been considered, whose solution was confirmed by experimental data measured on an Y-Ba-Cu-O sample. The magnetic diffusion equation has been solved for a description of the magnetic induction profiles in an increasing external magnetic field. The dynamic anomalies of the current-voltage characteristics have been then predicted, in agreement with experimental observations. The model taking into account the influence of the vortex-pinning center interaction on the magnetic field dependence of the critical current, has been also applied successfully for description of the anomalies.