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

100%

Khan P. M. , Raj A. , Alam M. I. , Chakraborty S. , Roy S.

Biocybernetics and Biomedical Engineering

2023

tom 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.

New generation impedance rheographs and examples of their clinical applications

80%

Pałko T.

Biocybernetics and Biomedical Engineering

2007

tom Vol. 27, no. 1-2

185-196

The impedance rheography as a method of measurement and recording of electrical impedance and its changes in a body segment is widely used in research and medical practice. Several types, single or multichannel, analog or digital impedance rheographs were developed at Warsaw University of Technology. A digital impedance rheograph has been recently designed for measurement of impedance modulus (...) and its changes (...) of body segment or tissue sequent simultaneously with ECG signal. The designed rheographs were positively tested technically and clinically. In this article is presented the clinical application of impedance rheography for study of systemic and pulmonary blood flow in two different groups of patients with several cardiac abnormalities or after therapeutic procedures. The investigation of systemic blood circulation was done on group of 20 patients with cardiac arrhythmia (15 cardioverted and 5 cardiostimulated patients). The pulmonary blood circulation was studied on 20 healthy and 26 patients: 8 with isolated pulmonary stenosis and 18 with Fallot syndrome. The findings show that impedance method allows to detect and assess these abnormalities.

Mathematical analysis of mass and heat transfer through arterial stenosis

80%

Hussain A. , Sarwar L. , Akbar S. , Malik M. Y.

Journal of Power Technologies

2022

tom Vol. 102, nr 3

88--95

The article investigates the steady state flow of an incompressible fluid which is treated as a Williamson fluid through a stenoised region in the shape of cosine constriction. Blood is taken as a Williamson fluid. Mathematical formulation leads us to nonlinear compatibility and energy equations, which are then deciphered by the shooting technique to obtain the numerical solution. Suitable resemblance transformations are used to change partial differential equations into an embellished form of ordinary differential equations. Further, the consequences of the different parameters involved are shown by graphs and a conclusion is presented. Velocity and temperature fields are canvassed graphically for the distinct values of emerging parameters and discussed in tabular form. Skin friction and the coefficient of heat transfer are also covered in the discussion. The resulting Nusselt number curve exhibits negative deflection for variational values of λ and height of the stenosis δ.