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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

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2024

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Vol. 18, no. 1

8--21

EN

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.

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A review of technologies in the area of production, storage and use of hydrogen in the automotive industry

Małek Arkadiusz, Karowiec Marek, Jóźwik Krzysztof

Archiwum Motoryzacji

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2023

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Vol. 102, nr 4

41--67

EN

Presently, we can learn and read more and more about hydrogen in both traditional and social media. The article answers why there is so much interest in hydrogen recently. It has been recognized by European and global decision-makers as a very promising medium necessary to carry out the climate and energy transformation. The advantages of hydrogen as a fuel and as a medium for storing large amounts of energy over a longer period of time is also presented. In addition, an overview of hydrogen technologies presented at the Hydrogen Technology Expo in Bremen in September 2023 is provided. The state of hydrogen technologies currently available on the market is compared to the latest achievements of scientists described in scientific articles. The aim of the article is to review the technologies available on the market for the production, storage and use of hydrogen as a vehicle fuel. Hydrogen technologies presented at the Hydrogen Expo in Bremen were confronted with the latest scientific achievements described in the latest scientific articles. Thanks to such a confrontation, it is possible to make a rational purchasing decision in the area of selected hydrogen technologies.

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Experimental investigations of the PMMA bone cement distribution inside a model of lumbar vertebrae

Bonik Artur, Tyfa Zbigniew, Ciupik Lechosław Franciszek, Sobczak Krzysztof, Kierzkowska Agnieszka, Obidowski Damian Stanisław, Witkowski Dariusz, Pałczyński Tomasz, Elgalal Marcin, Komorowski Piotr, Słoński Edward, Jóźwik Krzysztof, Walkowiak Bogdan

Engineering of Biomaterials

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2022

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vol. 25, no. 165

23--30

EN

The use of bone cement in procedures such as vertebroplasty and kyphoplasty can reduce pain and mechanically support the spine. This study aimed to evaluate whether air entrapped within bone cement affected its distribution in a vertebral body model. The study included 3D printed anatomical models of vertebrae together with their internal trabecular structure. Aeration was achieved by mixing the bone cement using three different altered procedures, whilst the control sample was prepared according to the manufacturer’s instructions. The further two samples were prepared by reducing or increasing the number of cycles required to mix the bone cement. A test rig was used to administer the prepared bone cement and introduce it into the vertebral model. Each time the injection was stopped when either the cement started to flow out of the vertebral model or when the entire cement volume was administered. The computer tomography (CT) scanning was performed to evaluate aerification and its influence on the bone cement distribution in each of the patient-specific models. The large number of small pores visible within the cement, especially in the cannula vicinity, indicated that the cement should not be treated as a homogenous liquid. These results suggest that a high level of aerification can influence the further cement distribution.

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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

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2022

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Vol. 42, no. 1

375--390

EN

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.

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Application of overset mesh approach in the investigation of the Savonius wind turbines with rigid and deformable blades

Marchewka Emil, Sobczak Krzysztof, Reorowicz Piotr, Obidowski Damian Stanisław, Jóźwik Krzysztof

Archives of Thermodynamics

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2021

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Vol. 42, no 4

201--216

EN

Machines utilising renewable energy constantly undergo research aimed at raising their efficiency. One of them is a Savonius wind turbine, where scientists propose adjustments to improve its aerodynamic properties. At present, their assessment is usually performed by means of transient computational fluid dynamics simulations with two- or threedimensional models. In this paper, the overset (chimera) mesh approach was applied to investigate the performance of a Savonius wind turbine equipped with deformable blades. They were continuously deformed during rotation by a dedicated mechanism to increase a positive torque of the advancing blade, and meanwhile, decrease a negative torque of the returning blade. A quasi-two-dimensional model with a two-way fluid-structure interaction method was applied, where the structural solver determined blade deflection caused by the predefined deformation mechanism and aerodynamic loads, whereas the coupled computational fluid dynamics solver determined the transient flow. The deformable blades rotor performance was calculated and compared with a conventional rigid Savonius turbine, both simulated using the overset mesh approach. The average value of the power coefficient achieved a 55% rise in the case of deformable blades turbine. Additionally, to validate the overset method, its results were compared with the classical sliding mesh method for a conventional rigid rotor.

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A two-stage model of an arteriovenous fistula maturation process

Jodko Daniel M., Obidowski Damian S., Reorowicz Piotr, Jóźwik Krzysztof

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 2

139--153

EN

Purpose: An arteriovenous fistula has been a widely accepted vascular access for hemodialysis, however, a fistula maturation process is still not fully understood. In the short period of time, right after vein and artery shunting, the physical and biological changes take place mainly in the venous wall. A two-stage modeling method of arteriovenous fistula maturation process was proposed and presented. Methods: The first stage of the maturation was modeled with two-way coupled fluid structure interaction computer simulations. Whereas for the second, biological stage, a model was based on the change in the elasticity of the venous wall due to wall shear stress (WSS) modifications. Results: The relation between stress and radial and circumferential strain, based on Lame’s theory, makes possible to introduce a mathematical model defining modulus of elasticity, averaged WSS, and venous diameter as time functions. The presented model enables one to predict changes in the monitored parameters in the arteriovenous fistula taking place in the time longer than 90 days. Conclusions: We found that probably the majority of fistulas can be assessed to be mature too early, when the adequate blood flow rate is achieved but mean WSS still remains at the non-physiological level (>10 Pa).