2 research outputs found
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Severity parameter and global importance factor of non-newtonian models in 3D reconstructed human left coronary artery
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The capabilities and limitations of various molecular viscosity models, when testing Left Coronary Artery (LCA) tree, were analyzed via: molecular viscosity, local and global non-Newtonian importance factors, Wall Shear Stress (WSS) and Wall Shear Stress Gradient (WSSG). Seven non-Newtonian molecular viscosity models, plus the Newtonian one, were compared. Dense grid of 620000 nodes located, mostly, at near to low WSS flow regions (endothelium regions) is needed for current LCA application. The WSS
distribution yields a consistent LCA pattern for nearly all non-Newtonian models. High molecular viscosity, low WSS low WSSG values appear at proximal LCA regions at the outer walls of the major bifurcation. The global importance factor for the non-Newtonian power law model yields 76.7% (non-Newtonian flow), while for the Generalized power law model this value is 6.1% (Newtonian flow). The capabilities of the applied non-Newtonian law models appear at low strain rates. The Newtonian blood flow treatment is considered to be a good approximation at mid-and high-strain rates. In general, the non-Newtonian power law and the Generalized power law blood viscosity models are considered to approximate the molecular viscosity and WSS calculations in a more satisfactory way
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Wall shear stress and low density lipoprotein concentration in stented arteries
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Current computational analysis results quantify Wall Shear Stress (WSS) and its impact on Low Density Lipoprotein (LDL) concentration of a fully deployed straight artery stent. Atherosclerosis shows
predilection in arterial regions with hemodynamic particularities, as local disturbances of WSS in space, and locally high concentrations of lipoprotein. The WSS and subsequently the LDL distribution are important indicators of stent performance. A typical 6.0 mm diameter straight stented artery is used to elucidate the WSS and the LDL transport under steady flow conditions treating the blood as a non-Newtonian fluid. Struts are 50.0 % embedded into the arterial wall. Emphasis is placed in the LDL distribution at the upstream and downstream flow regions of each strut intersection. Reduced WSS values are observed towards outlet. At the strut intersections, high WSS values are observed possibly causing platelet activation. Prone to plaque development are flow regions located at specific strut intersections (mostly at the vicinity of the curved struts) where increased LDL concentration is observed. The maximum LDL concentration over the stented artery reaches a value of 3.8 % higher than that at the entrance. The concentration at distal to any strut region was higher than proximal to the strut