The pulsatile blood flow through human aortic arch and three major branches are computationally studied to investigate the effect of blood rheology on the hemodynamic parameters. The human aorta model is reconstructed from the computed tomography (CT) images of specific patient. The results of nine non-Newtonian (Casson, K-L, Modified Casson, Carreau, Carreau-Yasuda, Cross, Power-law, Modified Power-law, and Generalized Power-law) models are analyzed and compared with those of Newtonian model and reveal very interesting hemodynamic features for each model. Among the applied non-Newtonian models, the Cross model displays significantly different distribution of wall shear stress (WSS) and velocity field through the aorta at diastole. Comparing the local shear stress magnitude in three branches at different critical cardiac instants shows that the shear thinning nature of blood can slightly influence WSS at diastole, in all branches. The effect of blood rheology appears clearly in the brachiocephalic and carotid branches, at peak systole. In the high-shear rate zones, the lowest WSS is estimated by the Carreau model. The Newtonian model has close prediction to the Cross model at peak systole. The power law model predictions remain the nearest to those of the Carreau model along the cardiac cycle.

Effect of rheological models on the hemodynamics within human aorta: CFD study on CT image-based geometry

The rupture risk of unruptured intracranial aneurysms is known to be dependent on the size of the aneurysm. However, the association of morphological characteristics with ruptured aneurysms has not been established in a systematic and location specific manner for the most common aneurysm locations. We evaluated posterior communicating artery (PCoA) aneurysms for morphological parameters associated with aneurysm rupture in that location. CT angiograms were evaluated to generate 3-D models of the aneurysms and surrounding vasculature. Univariate and multivariate analyses were performed to evaluate morphological parameters including aneurysm volume, aspect ratio, size ratio, distance to ICA bifurcation, aneurysm angle, vessel angles, flow angles, and vessel-to-vessel angles. From 2005–2012, 148 PCoA aneurysms were treated in a single institution. Preoperative CTAs from 63 patients (40 ruptured, 23 unruptured) were available and analyzed. Multivariate logistic regression revealed that smaller volume (p = 0.011), larger aneurysm neck diameter (0.048), and shorter ICA bifurcation to aneurysm distance (p = 0.005) were the most strongly associated with aneurysm rupture after adjusting for all other clinical and morphological variables. Multivariate subgroup analysis for patients with visualized PCoA demonstrated that larger neck diameter (p = 0.018) and shorter ICA bifurcation to aneurysm distance (p = 0.011) were significantly associated with rupture. Intracerebral hemorrhage was associated with smaller volume, larger maximum height, and smaller aneurysm angle, in addition to lateral projection, male sex, and lack of hypertension. We found that shorter ICA bifurcation to aneurysm distance is significantly associated with PCoA aneurysm rupture. This is a new physically intuitive parameter that can be measured easily and therefore be readily applied in clinical practice to aid in the evaluation of patients with PCoA aneurysms.

/pdf/morphological-parameters-associated-with-ruptured-posterior-43q56wkzo1.pdf

Morphological Parameters Associated with Ruptured Posterior Communicating Aneurysms

Computer modeling of pulsatile blood flow in elastic artery using a software program for application in biomedical engineering.

Numerical simulation of electro-deposition process influenced by force convection and migration of ions

Micro-mixers are considered as vital components of Micro Total Analysis systems (μTAS). Major objective in the design of micro-mixers is achieving high mixing quality in short mixing times. In this paper, numerical simulation of some micro-mixer designs has been carried out to understand the detailed flow pattern and thereby to propose modifications for improving mixing efficiency. It is well known that inducing convection will provide turbulent like behavior with corresponding mixing enhancement. In micro systems to drive the flow, electro-osmotic force is usually used by introducing electrodes. In this work, mixing electrodes have been implemented to induce convection and eddies. This numerical study addresses the problem by solving the system of inter-coupled Poisson-Nernst-Planck-Navier-Stokes equations using Rayan (in-house code). These equations compared to their simplified forms, provide much more realistic physical description by including diffusion, electro-migration and convection mechanisms. In cases of active AC electrodes, all of these mechanisms play important roles. The traditional Poisson-Boltzmann model loses its accuracy in cases of complex geometry or AC electrodes especially with high frequencies. As a result of modifications proposed herein by strategic placement of vertical and horizontal electrodes and extending mixing chamber length a mixing quality of 96.2% was achieved just in 1.8 s.

Enhancing active electro-kinetic micro-mixer efficiency by introducing vertical electrodes and modifying chamber aspect ratio

http://scientiairanica.sharif.edu/article_3334_052f2c031c118984455c39da20abc0a6.pdf

Investigation of wall shear stress related factors in realistic carotid bifurcation geometries and different flow conditions

http://scientiairanica.sharif.edu/article_3367_f2c50c87a594dc727c58233e2cb59c47.pdf

Rayan: A Polyhedral Grid Co-located Incompressible Finite Volume Solver (Part I: Basic Design Features)

http://scientiairanica.sharif.edu/article_3366_e36d28a4ba6421f093e90c2c300e1e0c.pdf

Two-Dimensional Numerical Investigation of a Micro Combustor

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Papers

Investigation of wall shear stress related factors in realistic carotid bifurcation geometries and different flow conditions

Rayan: A Polyhedral Grid Co-located Incompressible Finite Volume Solver (Part I: Basic Design Features)

Two-Dimensional Numerical Investigation of a Micro Combustor