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Influence of fluid rheology on blood flow haemodynamics in patient-specific arterial networks of varied complexity - in-silico studies

Tyfa Zbigniew, Reorowicz Piotr, Obidowski Damian, Jóźwik Krzysztof

Acta Mechanica et Automatica

2024

Vol. 18, no. 1

8--21

Results obtained with computational fluid dynamics (CFD) rely on assumptions made during a pre-processing stage, including a mathematical description of a fluid rheology. Up to this date there is no clear answer to several aspects, mainly related to the question of whether and under what conditions blood can be simplified to a Newtonian fluid during CFD analyses. Different research groups present contradictory results, leaving the question unanswered. Therefore, the objective of this research was to perform steady-state and pulsatile blood flow simulations using eight different rheological models in geometries of varying complexity. A qualitative comparison of shear- and viscosity-related parameters showed no meaningful discrepancies, but a quantitative analysis revealed significant differences, especially in the magnitudes of wall shear stress (WSS) and its gradient (WSSG). We suggest that for the large arteries blood should be modelled as a non-Newtonian fluid, whereas for the cerebral vasculature the assumption of blood as a simple Newtonian fluid can be treated as a valid simplification.

Blood flow through the fusiform aneurysm treated with the Flow Diverter stent – Numerical investigations

Reorowicz Piotr, Tyfa Zbigniew, Obidowski Damian, Wiśniewski Karol, Stefańczyk Ludomir, Jóźwik Krzysztof, Levy Michael Lee

Biocybernetics and Biomedical Engineering

2022

Vol. 42, no. 1

375--390

The Flow Diverter is one of the methods used in the treatment of a fusiform aneurysm. While this method is popular in treating anomalies of the cerebral vasculature, it is not commonly used in the treatment of aortic aneurysms. The numerical simulation in a patient-specific model of the abdominal aortal aneurysm allowed us to investigate and visualize the hemodynamics of blood before and after stent implantation. Our custom software (updated version of MeMoS) was used to reproduce the vessel geometry on the basis of imported DICOM image sets. The blood flow was modeled as pulsatile and with non-Newtonian rheology. A velocity distribution, vorticity, a region of stagnation and wall shear stress were plotted to give an insight into the mechanism of operation of Flow Diverter stents. Additionally, a quantitative analysis of the blood distribution among chosen abdominal arteries for one full cardiac cycle was performed. A Flow Diverter stent implanted in the fusiform aneurysmal sack involving the abdominal aorta significantly changed the flow pattern in the region of the aneurysm, but it did not contribute to diminished flow to the renal arteries.

Inhaled drug airflow patterns and particles deposition in the paediatric respiratory tract

Tyfa Zbigniew, Jóźwik Paulina, Obidowski Damian, Reorowicz Piotr, Jodko Daniel, Kapka Krystyna, Makosiej Ryszard, Czkwianianc Elżbieta

Acta of Bioengineering and Biomechanics

2020

Vol. 22, no. 2

101--110

: The effectiveness of inhaled drugs is strictly related to areas reachable by drug particles. Unless particles reach the desired part of the bronchial tree, their influence might not meet the expectations. Consequently, the disease progress might not be stopped or even slowed down. Therefore, the primary objective of this research was to analyze the airflow patterns and particle deposition of a standard inhaled drug using computational fluid dynamics. Methods: The study was devoted to the analysis of the particle diameter influence on their deposition areas within the entire respiratory tract. Two patient-specific respiratory tract models, for 6 and 12-year-old patients, were reconstructed based on the computed tomography examinations. Numerical analyses were carried out as stationary ones with the constant inflow of the particles of various diameters (within the range of 1–50 μm). It was proven that depending on the particle size, their deposition within the respiratory tract varies significantly. Results: The vast majority of the particles with diameters over 20 μm is gathered on the walls of the throat, whereas particles of diameters 5–15 μm are accumulated mainly on the trachea walls, leaving the alveoli insufficiently supplied with the drug particles. Conclusions: The inhaled drug size cannot be treated as negligible factor during the drug spraying. An improper distribution of the particles might not inhibit the symptoms of the asthma. Numerical simulations may improve drugs selection and visualize their distribution along the airways, which might accelerate asthma treatment personalization.