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International Journal for Numerical Methods in Biomedical Engineering

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https://www.readbyqxmd.com/read/30226292/fluid-structure-interaction-simulations-of-venous-valves-a-monolithic-ale-method-for-large-structural-displacements
#1
S Calandrini, E Aulisa
Venous valves are bicuspidal valves that ensure that blood in veins only flows back to the heart. To prevent retrograde blood flow, the two intraluminal leaflets meet in the center of the vein and occlude the vessel. In fluid-structure interaction (FSI) simulations of venous valves, the large structural displacements may lead to mesh deteriorations and entanglements, causing instabilities of the solver and, consequently, the numerical solution to diverge. In this paper, we propose an Arbitrary Lagrangian-Eulerian (ALE) scheme for FSI simulations designed to solve these instabilities...
September 18, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30216704/an-optimized-procedure-to-develop-a-three-dimensional-microfluidic-hydrogel-with-parallel-transport-networks
#2
Mahboubeh Jafarkhani, Zeinab Salehi, Mohammad Ali Shokrgozar, Shohreh Mashayekhan
The development of microfluidic hydrogels is an attractive method to generate continues perfusion, induce vascularization, increase solutes delivery and ultimately improve cell viability. However, the transport processes in many in vitro studies still have not been realized completely. To address this problem, we have developed a micro-channeled hydrogel with different collagen type I concentration of 1, 2 and 3 wt.% and assessed its physical properties and obtained diffusion coefficient of nutrient within the hydrogel...
September 14, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30211982/the-fda-nozzle-benchmark-in-theory-there-is-no-difference-between-theory-and-practice-but-in-practice-there-is
#3
A W Bergersen, M Mortensen, K Valen-Sendstad
The utility of flow simulations relies on the robustness of computational fluid dynamics (CFD) solvers and reproducibility of results. The aim of this study was to validate the Oasis CFD solver against in-vitro experimental measurements of jet breakdown location from the FDA nozzle benchmark at Reynolds number 3500, which is in the particularly-challenging transitional regime. Simulations were performed on meshes consisting of 5, 10, 17 and 28 million (M) tetrahedra, with Δt = 10-5 seconds. The 5 and 10M simulation jets broke down in reasonable agreement with the experiments...
September 13, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30203927/computational-aeroacoustics-to-identify-sound-sources-in-the-generation-of-sibilant-s
#4
Arnau Pont, Oriol Guasch, Joan Baiges, Ramon Codina, Annemie Van Hirtum
A sibilant fricative /s/ is generated when the turbulent jet in the narrow channel between the tongue blade and the hard palate is deflected downwards through the space between the upper and lower incisors, and then impinges the space between the lower incisors and the lower lip. The flow eddies in that region become a source of direct aerodynamic sound, which is also diffracted by the speech articulators and radiated outwards. The numerical simulation of these phenomena is complex. The spectrum of an /s/ typically peaks between 4 - 10 kHz, which implies that very fine computational meshes are needed to capture the eddies producing such high frequencies...
September 11, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30198152/variational-data-assimilation-for-transient-blood-flow-simulations-cerebral-aneurysms-as-an-illustrative-example
#5
S W Funke, M Nordaas, Ø Evju, M S Alnaes, K A Mardal
Several cardiovascular diseases are caused from localised abnormal blood flow such as in the case of stenosis or aneurysms. Prevailing theories propose that the development is caused by abnormal wall-shear stress in focused areas. Computational fluid mechanics have arisen as a promising tool for a more precise and quantitative analysis, in particular because the anatomy is often readily available even by standard imaging techniques such as magnetic resonance and computed tomography angiography. However, computational fluid mechanics rely on accurate initial and boundary conditions which are difficult to obtain...
September 10, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30188608/kinematic-boundary-conditions-substantially-impact-in-silico-ventricular-function
#6
Mathias Peirlinck, Kevin Sack, Pieter De Backer, Pedro Morais, Patrick Segers, Thomas Franz, Matthieu De Beule
No abstract text is available yet for this article.
September 6, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30171673/finite-element-modeling-of-near-wall-mass-transport-in-cardiovascular-flows
#7
Kirk Hansen, Amirhossein Arzani, Shawn Shadden
Many cardiovascular processes involve mass transport between blood and the vessel wall. Finite element methods are commonly used to numerically simulate these processes. Cardiovascular mass transport problems are typically characterized by high Péclet numbers, requiring fine near-wall mesh resolution as well as the use of stabilization techniques to avoid numerical instabilities. In this work, we develop a set of guidelines for solving high-Péclet-number near-wall mass transport problems using the finite element method...
September 1, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30161296/reducing-stress-concentration-on-the-cup-rim-of-hip-implants-under-edge-loading
#8
M S Uddin, G W C Chan
High stress concentration under edge loading on the cup rim contact due to micro-separation causes accelerated striping wear, fracture, and fatigue in hip implant components. While continuous effort is devoted into improving bearing design and surgical procedure to tackle the problem, the concern still has remained forcing biomedical engineers to seek for new and alternative solutions. The current paper aims to investigate the effect of a new geometry 'spline' introduced at the cup's rim corner to minimize stress concentration under edge loading...
August 30, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30152120/a-comparative-study-of-porous-medium-cfd-models-for-flow-diverter-stents-advantages-and-short-comings
#9
Nicolás Dazeo, Javier Dottori, Gustavo Boroni, Ignacio Larrabide
In Computational Fluid Dynamics, there is a high interest in modeling flow diverter stents as porous media due to its reduced computational loads. One of the main difficulties of such models is proper parameter setup. Most authors assume flow diverter's wire screen as an isotropic and homogeneous medium, while others proposes anisotropic configurations, yet very little is discussed about the effect of these assumptions on model's accuracy. In this paper, we compare the effect of different models on hemodynamics in relation to their parameters...
August 27, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30151998/assessment-of-wall-stresses-and-mechanical-heart-power-in-the-left-ventricle-finite-element-modeling-versus-laplace-analysis
#10
Matthias A F Gsell, Christoph M Augustin, Anton J Prassl, Elias Karabelas, Joao F Fernandes, Marcus Kelm, Leonid Goubergrits, Titus Kuehne, Gernot Plank
INTRODUCTION: Stenotic aortic valve disease (AS) causes pressure overload of the left ventricle (LV) that may trigger adverse remodeling and precipitate progression towards heart failure (HF). As myocardial energetics can be impaired during AS, LV wall stresses and biomechanical power provide a complementary view of LV performance that may aide in better assessing the state of disease. OBJECTIVES: Using a high-resolution electro-mechanical (EM) in silico model of the LV as a reference, we evaluated clinically feasible Laplace-based methods for assessing global LV wall stresses and biomechanical power...
August 27, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30133180/a-noninvasive-method-for-the-determination-of-in-vivo-mitral-valve-leaflet-strains
#11
Bruno V Rego, Amir H Khalighi, Andrew Drach, Eric K Lai, Alison M Pouch, Robert C Gorman, Joseph H Gorman, Michael S Sacks
Assessment of mitral valve (MV) function is important in many diagnostic, prognostic, and surgical planning applications for treatment of MV disease. Yet, to date, there are no accepted noninvasive methods for determination of MV leaflet deformation, which is a critical metric of MV function. In this study, we present a novel, completely noninvasive computational method to estimate MV leaflet in-plane strains from clinical-quality real-time three-dimensional echocardiography (rt-3DE) images. The images were first segmented to produce meshed medial-surface leaflet geometries of the open and closed states...
August 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30133172/fully-coupled-numerical-model-of-actin-treadmilling-in-the-lamellipodium-of-the-cell
#12
K S Kollepara, P D Mulye, P Saez
Cells rely on an interplay of subcellular elements for motility and migration. Certain regions of motile cells, such as the lamellipodium, are made of a complex mixture of actin monomers and filaments which polymerize at the front of the cell, close to the cell membrane, and depolymerize at the rear. The dynamic actin turnover induces the so-called intracellular retrograde flow and it is a fundamental process for cell motility. Apart from some comprehensive mathematical models, the computational modelling of actin treadmilling has been based on simpler biophysical models...
August 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30133165/a-novel-method-to-generate-dynamic-boundary-conditions-for-airway-cfd-by-mapping-upper-airway-movement-with-non-rigid-registration-of-dynamic-and-static-mri
#13
Alister J Bates, Andreas Schuh, Keith McConnell, Brynne M Williams, J Matthew Lanier, Matthew M Willmering, Jason C Woods, Robert J Fleck, Charles L Dumoulin, Raouf S Amin
Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all...
August 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30117302/fully-coupled-fluid-electro-mechanical-model-of-the-human-heart-for-supercomputers
#14
Alfonso Santiago, Miguel Zavala-Aké, Jazmín Aguado-Sierra, Ruben Doste, Samuel Gómez, Ruth Arís, Juan C Cajas, Eva Casoni, Mariano Vázquez
In this work we present a fully coupled fluid-electro-mechanical model of a 50th percentile human heart. The model is implemented on Alya, the BSC multi-physics parallel code, capable of running efficiently in supercomputers. Blood in the cardiac cavities is modelled by the incompressible Navier-Stokes equations and an Arbitrary Lagrangian-Eulerian (ALE) scheme. Electrophysiology is modelled with a monodomain scheme and the O'Hara-Rudy cell model. Solid mechanics is modelled with a total-Lagrangian formulation for discrete strains using the Holzapfel-Ogden cardiac tissue material model...
August 16, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30101520/a-novel-patient-oriented-numerical-procedure-for-glaucoma-drainage-devices
#15
Alessandro Mauro, Nicola Massarotti, Salahudeen Mohamed, Ignacio Rodríguez Uña, Mario R Romano, Vito Romano
The present work analyses the performance of four glaucoma drainage devices, by means of a novel patient-oriented numerical procedure. The procedure is based on the three-dimensional geometry reconstruction from the stacks of tomographic images of a human eye, at different angles, on meshing and on thermo-fluid dynamics modelling activities, carried out on the reconstructed computational domain. The current three-dimensional eye model considers Anterior Chamber (AC), Trabecular Meshwork (TM), Schlemm's Canal (SC) and Collector Channels (CC), making use of Generalized Porous Medium (GPM) approach for modelling ocular porous tissue and cavities...
August 12, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30070071/a-transmurally-heterogeneous-orthotropic-activation-model-for-ventricular-contraction-and-its-numerical-validation
#16
L Barbarotta, L Dedè, S Rossi, A Quarteroni
Models for cardiac mechanics require an activation mechanism properly representing the stress-strain relations in the contracting myocardium. In this paper, we propose a new activation model which accounts for the transmural heterogeneities observed in myocardial strain measurements. In order to take the anisotropy of the active mechanics into account, our model is based on an active strain formulation. Thanks to multiplicative decomposition of the deformation gradient tensor, in this formulation the active strains orthogonal to the fibers can be naturally described...
August 2, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30070046/a-coupled-approach-for-fluid-saturated-poroelastic-media-and-immersed-solids-for-modeling-cell-tissue-interactions
#17
Andreas D Rauch, Anh-Tu Vuong, Lena Yoshihara, Wolfgang A Wall
In this paper, we propose a finite element-based immersed method to treat the mechanical coupling between a deformable porous medium model (PM) and an immersed solid model (ISM). The PM is formulated as a homogenized, volume-coupled two-field model, comprising a nearly incompressible solid phase that interacts with an incompressible Darcy-Brinkman flow. The fluid phase is formulated with respect to the Lagrangian finite element mesh, following the solid phase deformation. The ISM is discretized with an independent Lagrangian mesh and may behave arbitrarily complex (it may, eg, be compressible, grow, and perform active deformations)...
August 2, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30070031/on-the-monolithic-and-staggered-solution-of-cell-contractility-and-focal-adhesion-growth
#18
Pradeep Keshavanarayana, Martin Ruess, René de Borst
The mechanical response of cells to stimuli tightly couples biochemical and biomechanical processes, which describe fundamental properties such as cell growth and reorientation. Cells interact continuously with their external surroundings, the extracellular matrix (ECM), by establishing a bond between cell and ECM through the formation of focal adhesions. Focal adhesions are made up of integrins, which are mechanosensitive proteins and responsible for the communication between the cell and the ECM. The governing biochemomechanical processes can be modeled by means of a continuum approach considering mechanical and thermodynamic equilibrium to describe cell contractility and focal adhesion growth...
August 2, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30070048/morphological-and-hemodynamical-alterations-in-brachial-artery-and-cephalic-vein-an-image-based-study-for-preoperative-assessment-for-vascular-access-creation
#19
Nicolas Aristokleous, J Graeme Houston, Leonard D Browne, Stephen P Broderick, Efstratios Kokkalis, Stephen J Gandy, Michael T Walsh
The current study aims to computationally evaluate the effect of right upper arm position on the geometric and hemodynamic characteristics of the brachial artery (BA) and cephalic vein (CV) and, furthermore, to present in detail the methodology to characterise morphological and hemodynamical healthy vessels. Ten healthy volunteers were analysed in two configurations, the supine (S) and the prone (P) position. Lumen 3D surface models were constructed from images acquired from a non-contrast MRI sequence. Then, the models were used to numerically compute the physiological range of geometric (n = 10) and hemodynamic (n = 3) parameters in the BA and CV...
August 1, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30062843/patient-specific-cfd-modelling-in-the-thoracic-aorta-with-pc-mri-based-boundary-conditions-a-least-square-three-element-windkessel-approach
#20
Rodrigo M Romarowski, Adrien Lefieux, Simone Morganti, Alessandro Veneziani, Ferdinando Auricchio
The increasing use of computational fluid dynamics for simulating blood flow in clinics demands the identification of appropriate patient-specific boundary conditions for the customization of the mathematical models. These conditions should ideally be retrieved from measurements. However, finite resolution of devices as well as other practical/ethical reasons prevent the construction of complete data sets necessary to make the mathematical problems well posed. Available data need to be completed by modelling assumptions, whose impact on the final solution has to be carefully addressed...
July 31, 2018: International Journal for Numerical Methods in Biomedical Engineering
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