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Computational fluid dynamics

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https://www.readbyqxmd.com/read/29352582/a-microfluidic-distributor-combining-minimal-volume-minimal-dispersion-and-minimal-sensitivity-to-clogging
#1
Sander Jespers, Sander Deridder, Gert Desmet
A new type of microfluidic flow distributor (referred to as the mixed mode or MM-distributor) is proposed. Its performance characteristics are determined using computational fluid dynamics (CFD), both in the absence and the presence of clogging, which is an important problem in microfluidic systems. A comparison is made with two existing, well-performing distributor types: the bifurcating (BF) distributor and an optimized diverging distributor, the so-called radially interconnected (RI) distributor. It was found that, in the absence of clogging, the MM-distributor produces only a little more dispersion than the bifurcating (BF) distributor, but much less than the radially interconnected (RI) distributor...
January 12, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/29352062/critical-role-of-angiographic-acquisition-modality-and-reconstruction-on-morphometric-and-haemodynamic-analysis-of-intracranial-aneurysms
#2
Alexandra Lauric, James E Hippelheuser, Adel M Malek
BACKGROUND: Subtracted 3-D rotational angiography (3DRA) and cone-beam computed tomography angiography (CBCT-A) are often used in assessing cerebral aneurysm shape and haemodynamic profile. We sought to evaluate the effect of imaging modality, reconstruction parameters, and kernel selection on patient-derived aneurysm morphology and computational fluid dynamic (CFD) analysis to assess its potential contribution to inter-study variability. METHODS: Four patients (five aneurysms) underwent concurrent 3DRA followed by high-resolution CBCT-A...
January 19, 2018: Journal of Neurointerventional Surgery
https://www.readbyqxmd.com/read/29350200/leaf-templated-microwell-integrated-microfluidic-chips-for-high-throughput-cell-experiments
#3
Mao Mao, Jiankang He, Yongjie Lu, Xiao Li, Tianjiao Li, Wenxing Zhou, Dichen Li
As an alternative to conventional cell culture and animal testing, organ-on-a-chip is applied to study the biological phenomena of organ development and disease, as well as the interactions between human tissues and external stimuli such as chemicals, forces and electricity. The pattern design of microfluidic channel is one of the key approaches to regulate cell growth and differentiation, because these channels work as a crucial vasculature system to control the fluidic flow throughout the organ-on-a-chip device...
January 19, 2018: Biofabrication
https://www.readbyqxmd.com/read/29347684/scalable-and-fast-heterogeneous-molecular-simulation-with-predictive-parallelization-schemes
#4
Horacio V Guzman, Christoph Junghans, Kurt Kremer, Torsten Stuehn
Multiscale and inhomogeneous molecular systems are challenging topics in the field of molecular simulation. In particular, modeling biological systems in the context of multiscale simulations and exploring material properties are driving a permanent development of new simulation methods and optimization algorithms. In computational terms, those methods require parallelization schemes that make a productive use of computational resources for each simulation and from its genesis. Here, we introduce the heterogeneous domain decomposition approach, which is a combination of an heterogeneity-sensitive spatial domain decomposition with an a priori rearrangement of subdomain walls...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347451/computational-investigation-of-tb-iii-ion-line-intensities-in-single-bubble-sonoluminescence
#5
Jinfu Liang, Yu An
We perform a computational fluid dynamics simulation of trivalent terbium [Tb(III)] ion line emissions from single-bubble sonoluminescence (SBSL). Our simulation includes dynamic boundary conditions as well as the effects of gas properties and quenching by species, such as nitrite ion (NO_{2}^{-}). Simulation results demonstrate that when the maximum temperature inside a dimly luminescing bubble is relatively low, emission peaks from excited Tb(III) ions are prominent within the emission spectra. As the maximum temperature of the bubble increases, emission peaks of Tb(III) ions fade away relative to the continuum background emission...
December 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347398/forced-underwater-laminar-flows-with-active-magnetohydrodynamic-metamaterials
#6
Dean Culver, Yaroslav Urzhumov
Theory and practical implementations for wake-free propulsion systems are proposed and proven with computational fluid dynamic modeling. Introduced earlier, the concept of active hydrodynamic metamaterials is advanced by introducing magnetohydrodynamic metamaterials, structures with custom-designed volumetric distribution of Lorentz forces acting on a conducting fluid. Distributions of volume forces leading to wake-free, laminar flows are designed using multivariate optimization. Theoretical indications are presented that such flows can be sustained at arbitrarily high Reynolds numbers...
December 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347210/eigenvector-centrality-for-geometric-and-topological-characterization-of-porous-media
#7
Joaquin Jimenez-Martinez, Christian F A Negre
Solving flow and transport through complex geometries such as porous media is computationally difficult. Such calculations usually involve the solution of a system of discretized differential equations, which could lead to extreme computational cost depending on the size of the domain and the accuracy of the model. Geometric simplifications like pore networks, where the pores are represented by nodes and the pore throats by edges connecting pores, have been proposed. These models, despite their ability to preserve the connectivity of the medium, have difficulties capturing preferential paths (high velocity) and stagnation zones (low velocity), as they do not consider the specific relations between nodes...
July 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347101/formation-of-liquid-drops-at-an-orifice-and-dynamics-of-pinch-off-in-liquid-jets
#8
Manash Pratim Borthakur, Gautam Biswas, Dipankar Bandyopadhyay
This paper presents a numerical investigation of the dynamics of pinch-off in liquid drops and jets during injection of a liquid through an orifice into another fluid. The current study is carried out by solving axisymmetric Navier-Stokes equations and the interface is captured using a coupled level-set and volume-of-fluid approach. The delicate interplay of inertia and viscous effects plays a crucial role in deciding the dynamics of the formation as well as breakup of liquid drops and jets. In the dripping regime, the growth and breakup rate of a drop are studied and quantified by corroborating with theoretical predictions...
July 2017: Physical Review. E
https://www.readbyqxmd.com/read/29346937/uhlenbeck-ford-model-phase-diagram-and-corresponding-states-analysis
#9
Rodolfo Paula Leite, Pedro Antonio Santos-Flórez, Maurice de Koning
Using molecular dynamics simulations and nonequilibrium thermodynamic-integration techniques we compute the Helmholtz free energies of the body-centered-cubic (bcc), face-centered-cubic (fcc), hexagonal close-packed, and fluid phases of the Uhlenbeck-Ford model (UFM) and use the results to construct its phase diagram. The pair interaction associated with the UFM is characterized by an ultrasoft, purely repulsive pair potential that diverges logarithmically at the origin. We find that the bcc and fcc are the only thermodynamically stable crystalline phases in the phase diagram...
September 2017: Physical Review. E
https://www.readbyqxmd.com/read/29345035/pressure-and-pipes-from-neuroimaging-to-virtual-measurement
#10
Marialuisa Zedde, Rosario Pascarella
Leng et al. [1] described the practical application of a computational fluid dynamics (CFD) model based on Computed Tomography Angiography (CTA) in 85 patients with symptomatic atherosclerotic M1 middle cerebral artery (MCA) stenosis, to virtually measure arterial pressure (AP) across the stenotic segment, according to the theory that translesional pressure gradient (PG) drives arteriologenesis and leptomeningeal collaterals (LMC) development. This is a fundamental pathophysiological issue about the risk of recurrent stroke downstream an intracranial artery stenosis and both the degree of stenosis and the collateral circulation affect it; in WASID trial [2] patients with severe (> 70%) intracranial stenosis and efficient collaterals had a lower risk of recurrent stroke than patients with poor collaterals...
January 18, 2018: European Journal of Neurology: the Official Journal of the European Federation of Neurological Societies
https://www.readbyqxmd.com/read/29342856/calculation-and-identification-of-the-aerodynamic-parameters-for-small-scaled-fixed-wing-uavs
#11
Jieliang Shen, Yan Su, Qing Liang, Xinhua Zhu
The establishment of the Aircraft Dynamic Model(ADM) constitutes the prerequisite for the design of the navigation and control system, but the aerodynamic parameters in the model could not be readily obtained especially for small-scaled fixed-wing UAVs. In this paper, the procedure of computing the aerodynamic parameters is developed. All the longitudinal and lateral aerodynamic derivatives are firstly calculated through semi-empirical method based on the aerodynamics, rather than the wind tunnel tests or fluid dynamics software analysis...
January 13, 2018: Sensors
https://www.readbyqxmd.com/read/29341921/computational-hydrodynamic-comparison-of-a-mini-vessel-and-a-usp-2-dissolution-testing-system-to-predict-the-dynamic-operating-conditions-for-similarity-of-dissolution-performance
#12
Bing Wang, Gerard Bredael, Piero M Armenante
The hydrodynamics characteristics of a mini vessel and a USP 2 dissolution testing system were obtained and compared to predict the tablet-liquid mass transfer coefficient from velocity distributions near the tablet and establish the dynamic operating conditions under which dissolution in mini vessels could be conducted to generate concentration profiles similar to those in the USP 2. Velocity profiles were obtained experimentally using Particle Image Velocimetry (PIV). Computational Fluid Dynamics (CFD) was used to predict the velocity distribution and strain rate around a model tablet...
January 13, 2018: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/29340277/comparative-computed-flow-dynamic-analysis-of-different-optimization-techniques-in-left-main-either-provisional-or-culotte-stenting
#13
Gianluca Rigatelli, Fabio Dell'Avvocata, Marco Zuin, Sara Giatti, Khanh Duong, Trung Pham, Nguyen Si Tuan, Dobrin Vassiliev, Ramesh Daggubati, Thach Nguyen
Background and Objectives: Provisional and culotte are the most commonly used techniques in left main (LM) stenting. The impact of different post-dilation techniques on fluid dynamic of LM bifurcation has not been yet investigated. The aim of this study is to evaluate, by means of computational fluid dynamic analysis (CFD), the impact of different post-dilation techniques including proximal optimization technique (POT), kissing balloon (KB), POT-Side-POT and POT-KB-POT, 2-steps Kissing (2SK) and Snuggle Kissing balloon (SKB) on flow dynamic profile after LM provisional or culotte stenting...
December 2017: Journal of Translational Internal Medicine
https://www.readbyqxmd.com/read/29339623/effects-of-scale-and-froude-number-on-the-hydraulics-of-waste-stabilization-ponds
#14
Isabela De Luna Vieira, Jhonatan Barbosa Da Silva, Carlos Nobuyoshi Ide, Johannes Gérson Janzen
This paper presents the findings from a series of computational fluid dynamics simulations to estimate the effect of scale and Froude number on hydraulic performance and effluent pollutant fraction of scaled waste stabilization ponds designed using Froude similarity. Prior to its application, the model was verified by comparing the computational and experimental results of a model scaled pond, showing good agreement and confirming that the model accurately reproduces the hydrodynamics and tracer transport processes...
January 2018: Water Science and Technology: a Journal of the International Association on Water Pollution Research
https://www.readbyqxmd.com/read/29338059/hemodynamic-characteristics-of-hyperplastic-remodeling-lesions-in-cerebral-aneurysms
#15
Kazuhiro Furukawa, Fujimaro Ishida, Masanori Tsuji, Yoichi Miura, Tomoyuki Kishimoto, Masato Shiba, Hiroshi Tanemura, Yasuyuki Umeda, Takanori Sano, Ryuta Yasuda, Shinichi Shimosaka, Hidenori Suzuki
BACKGROUND & PURPOSE: Hyperplastic remodeling (HR) lesions are sometimes found on cerebral aneurysm walls. Atherosclerosis is the results of HR, which may cause an adverse effect on surgical treatment for cerebral aneurysms. Previous studies have demonstrated that atherosclerotic changes had a correlation with certain hemodynamic characteristics. Therefore, we investigated local hemodynamic characteristics of HR lesions of cerebral aneurysms using computational fluid dynamics (CFD). METHODS: Twenty-four cerebral aneurysms were investigated using CFD and intraoperative video recordings...
2018: PloS One
https://www.readbyqxmd.com/read/29337433/numerical-simulation-of-two-consecutive-nasal-respiratory-cycles-toward-a-better-understanding-of-nasal-physiology
#16
Ludovic de Gabory, Nicolas Reville, Yannick Baux, Nicolas Boisson, Laurence Bordenave
BACKGROUND: Computational fluid dynamic (CFD) simulations have greatly improved the understanding of nasal physiology. We postulate that simulating the entire and repeated respiratory nasal cycles, within the whole sinonasal cavities, is mandatory to gather more accurate observations and better understand airflow patterns. METHODS: A 3-dimensional (3D) sinonasal model was constructed from a healthy adult computed tomography (CT) scan which discretized in 6.6 million cells (mean volume, 0...
January 16, 2018: International Forum of Allergy & Rhinology
https://www.readbyqxmd.com/read/29331827/pilot-scale-outdoor-photobioreactor-culture-of-the-marine-dinoflagellate-karlodinium-veneficum-production-of-a-karlotoxins-rich-extract
#17
L López-Rosales, A Sánchez-Mirón, F García-Camacho, A R Place, Yusuf Chisti, E Molina-Grima
A pilot-scale bioprocess was developed for the production of karlotoxin-enriched extracts of the marine algal dinoflagellate Karlodinium veneficum. A bubble column and a flat-panel photobioreactors (80-281 L) were used for comparative assessment of growth. Flow hydrodynamics and energy dissipation rates (EDR) in the bioreactors were characterized through robust computational fluid dynamic simulations. All cultures were conducted monoseptically outdoors. Bubble column (maximum cell productivity in semicontinuous operation of 58 × 103 cell mL-1 day-1) proved to be a better culture system for this alga...
December 30, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/29331127/molecular-hydrodynamics-vortex-formation-and-sound-wave-propagation
#18
Kyeong Hwan Han, Changho Kim, Peter Talkner, George Em Karniadakis, Eok Kyun Lee
In the present study, quantitative feasibility tests of the hydrodynamic description of a two-dimensional fluid at the molecular level are performed, both with respect to length and time scales. Using high-resolution fluid velocity data obtained from extensive molecular dynamics simulations, we computed the transverse and longitudinal components of the velocity field by the Helmholtz decomposition and compared them with those obtained from the linearized Navier-Stokes (LNS) equations with time-dependent transport coefficients...
January 14, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29331052/flow-pattern-analysis-in-type-b-aortic-dissection-patients-after-stent-grafting-repair-comparison-between-complete-and-incomplete-false-lumen-thrombosis
#19
Wan Naimah Wan Ab Naim, Poo Balan Ganesan, Zhonghua Sun, Jing Lei, Shirley Jansen, Shahrul Amry Hashim, Teik Kok Ho, Einly Lim
Endovascular stent graft repair has become a common treatment for complicated Stanford Type B aortic dissection in order to restore true lumen flow and induce false lumen thrombosis. Using computational fluid dynamics, this study reports the differences in flow patterns and wall shear stress distribution in complicated Stanford Type B aortic dissection patients after endovascular stent graft repair. Five patients were included in this study: two having more than 80% false lumen thrombosis (Group 1), while three others had less than 80% false lumen thrombosis (Group 2) within one year following endovascular repair...
January 13, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/29325136/haemodynamic-performance-of-afx-and-nellix-endografts-a-computational-fluid-dynamics-study
#20
Anastasios Raptis, Michalis Xenos, George Kouvelos, Athanasios Giannoukas, Miltiadis Matsagkas
OBJECTIVES: The objective of this study is to analyse the flow conditions in the AFX and Nellix endografts (EGs) accounting for their postimplantation configuration in patients with an endovascular aneurysm repair-treated abdominal aortic aneurysm. METHODS: We reconstructed post-endovascular aneurysm repair computed tomography scans of patients treated with an AFX or Nellix EG creating post-implantation EG models. We examined 16 patients, 8 in each group. The blood flow properties were obtained by computational fluid dynamics simulations and were subsequently compared with physiological infrarenal blood flow properties measured in 5 healthy subjects...
January 8, 2018: Interactive Cardiovascular and Thoracic Surgery
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