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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

2022

vol. 25, no. 165

23--30

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.

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

2021

Vol. 42, no 4

201--216

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.