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Computational fluid dynamics

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https://www.readbyqxmd.com/read/28938512/numerical-simulation-of-scaling-up-for-aec-mbrs-regarding-membrane-module-configurations-and-cyclic-aeration-modes
#1
Min Yang, Mengmeng Liu, Dawei Yu, Jiaxi Zheng, Zhichao Wu, Shuguang Zhao, Jiang Chang, Yuansong Wei
The airlift external circulation membrane bioreactors (AEC-MBRs) have been attracting attentions due to their capabilities of nutrient removal with lower energy demand and smaller footprint. The gap between laboratory study and full-scale AEC-MBRs regarding hydrodynamics needs to be addressed. In this study, impacts of seven design variables and cyclic aeration modes on hydrodynamics were studied for the scale-up of AEC-MBRs with computational fluid dynamics modelling. The results demonstrated that shear stress on membranes was 14...
September 6, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28932659/conduction-electrohydrodynamics-with-mobile-electrodes-a-novel-actuation-system-for-untethered-robots
#2
Vito Cacucciolo, Hiroki Shigemune, Matteo Cianchetti, Cecilia Laschi, Shingo Maeda
Electrohydrodynamics (EHD) refers to the direct conversion of electrical energy into mechanical energy of a fluid. Through the use of mobile electrodes, this principle is exploited in a novel fashion for designing and testing a millimeter-scale untethered robot, which is powered harvesting the energy from an external electric field. The robot is designed as an inverted sail-boat, with the thrust generated on the sail submerged in the liquid. The diffusion constant of the robot is experimentally computed, proving that its movement is not driven by thermal fluctuations, and then its kinematic and dynamic responses are characterized for different applied voltages...
September 2017: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
https://www.readbyqxmd.com/read/28929446/new-imaging-tools-in-cardiovascular-medicine-computational-fluid-dynamics-and-4d-flow-mri
#3
Keiichi Itatani, Shohei Miyazaki, Tokoki Furusawa, Satoshi Numata, Sachiko Yamazaki, Kazuki Morimoto, Rina Makino, Hiroko Morichi, Teruyasu Nishino, Hitoshi Yaku
Blood flow imaging is a novel technology in cardiovascular medicine and surgery. Today, two types of blood flow imaging tools are available: measurement-based flow visualization including 4D flow MRI (or 3D cine phase-contrast magnetic resonance imaging), or echocardiography flow visualization software, and computer flow simulation modeling based on computational fluid dynamics (CFD). MRI and echocardiography flow visualization provide measured blood flow but have limitations in temporal and spatial resolution, whereas CFD flow calculates the flow according to assumptions instead of flow measurement, and it has sufficiently fine resolution up to the computer memory limit, and it enables even virtual surgery when combined with computer graphics...
September 19, 2017: General Thoracic and Cardiovascular Surgery
https://www.readbyqxmd.com/read/28929325/computational-fluid-dynamics-cfd-analysis-of-airlift-bioreactor-effect-of-draft-tube-configurations-on-hydrodynamics-cell-suspension-and-shear-rate
#4
Sanjay B Pawar
The biomass productivity of microalgae cells mainly depends on the hydrodynamics of airlift bioreactor (ABR). Thus, the hydrodynamics of concentric tube ABR was initially studied using two-phase three-dimensional CFD simulations with the Eulerian-Lagrangian approach. The performance of ABR (17 L) was examined for different configurations of the draft tube using various drag models such as Grace, Ishii-Zuber, and Schiller-Naumann. The gas holdups in the riser and the downcomer were well predicted using E-L approach...
September 19, 2017: Bioprocess and Biosystems Engineering
https://www.readbyqxmd.com/read/28929246/a-numerical-study-of-the-hemodynamic-effect-of-the-aortic-valve-on-coronary-flow
#5
Shaily Wald, Alex Liberzon, Idit Avrahami
During diastole, coronary perfusion depends on the pressure drop between the myocardial tissue and the coronary origin located at the aortic root. This pressure difference is influenced by the flow field near the closing valve leaflets. Clinical evidence is conclusive that patients with severe aortic stenosis (AS) suffer from diastolic dysfunction during hyperemia, but show increased coronary blood flow (CBF) during rest. Transcatheter aortic valve implantation (TAVI) was shown to decrease rest CBF along with its main purpose of improving the aortic flow and reducing the risk of heart failure...
September 19, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28926310/coronary-ct-angiography-derived-fractional-flow-reserve
#6
Christian Tesche, Carlo N De Cecco, Moritz H Albrecht, Taylor M Duguay, Richard R Bayer, Sheldon E Litwin, Daniel H Steinberg, U Joseph Schoepf
Invasive coronary angiography (ICA) with measurement of fractional flow reserve (FFR) by means of a pressure wire technique is the established reference standard for the functional assessment of coronary artery disease (CAD) ( 1 , 2 ). Coronary computed tomographic (CT) angiography has emerged as a noninvasive method for direct assessment of CAD and plaque characterization with high diagnostic accuracy compared with ICA ( 3 , 4 ). However, the solely anatomic assessment provided with both coronary CT angiography and ICA has poor discriminatory power for ischemia-inducing lesions...
October 2017: Radiology
https://www.readbyqxmd.com/read/28923473/virtual-surgery-for-patients-with-nasal-obstruction-use-of-computational-fluid-dynamics-mecomland-%C3%A2-digbody-%C3%A2-noseland-%C3%A2-to-document-objective-flow-parameters-and-optimise-surgical-results
#7
Manuel A Burgos, Maria Agustina Sevilla García, Enrique Sanmiguel Rojas, Carlos Del Pino, Carlos Fernández Velez, Francisco Piqueras, Francisco Esteban Ortega
INTRODUCTION: Computational fluid dynamics (CFD) is a mathematical tool to analyse airflow. We present a novel CFD software package to improve results following nasal surgery for obstruction. METHODS: A group of engineers in collaboration with otolaryngologists have developed a very intuitive CFD software package called MeComLand®, which uses the patient's cross-sectional (tomographic) images, thus showing in detail results originated by CFD such as airflow distributions, velocity profiles, pressure, or wall shear stress...
September 15, 2017: Acta Otorrinolaringológica Española
https://www.readbyqxmd.com/read/28920099/fast-virtual-fractional-flow-reserve-based%C3%A2-upon-steady-state-computational-fluid-dynamics-analysis-results-from-the-virtu-fast-study
#8
Paul D Morris, Daniel Alejandro Silva Soto, Jeroen F A Feher, Dan Rafiroiu, Angela Lungu, Susheel Varma, Patricia V Lawford, D Rodney Hose, Julian P Gunn
Fractional flow reserve (FFR)-guided percutaneous intervention is superior to standard assessment but remains underused. The authors have developed a novel "pseudotransient" analysis protocol for computing virtual fractional flow reserve (vFFR) based upon angiographic images and steady-state computational fluid dynamics. This protocol generates vFFR results in 189 s (cf >24 h for transient analysis) using a desktop PC, with <1% error relative to that of full-transient computational fluid dynamics analysis...
August 2017: JACC. Basic to Translational Science
https://www.readbyqxmd.com/read/28919576/simulation-of-the-effects-of-oxygen-carriers-and-scaffold-geometry-on-oxygen-distribution-and-cell-growth-in-a-channeled-scaffold-for-engineering-myocardium
#9
Alireza Zehi Mofrad, Shohreh Mashayekhan, Dariush Bastani
This study proposes a mathematical model to evaluate the impact of oxygen carriers and scaffold geometry on oxygen distribution and cell growth in a 3D cardiac construct using computational fluid dynamics (CFD). Flow equations, oxygen balance equation and cell balance equation were solved using special initial and boundary conditions. The modeling results revealed that 55% increase in cardiac cell density occurred by using 6.4% perfluorocarbon oxygen carrier (PFC) compared to pure culture medium without PFC supplementation...
September 14, 2017: Mathematical Biosciences
https://www.readbyqxmd.com/read/28918876/evaluation-of-potential-substrates-for-restenosis-and-thrombosis-in-overlapped-versus-edge-to-edge-juxtaposed-bioabsorbable-scaffolds-insights-from-a-computed-fluid-dynamic-study
#10
Gianluca Rigatelli, Marco Zuin, Fabio Dell'Avvocata, Paolo Cardaioli, Dobrin Vassiliev, Miroslaw Ferenc, Nguyen Tuan Nghia, Thach Nguyen, Nicholas Foin
BACKGROUND/PURPOSE: Multiple BRSs and specifically the Absorb scaffold (BVS) (Abbott Vascular, Santa Clara, CA USA) have been often used to treat long diffuse coronary artery lesions. We evaluate by a computational fluid dynamic(CFD) study the impact on the intravascular fluid rheology on multiple bioabsorbable scaffolds (BRS) by standard overlapping versus edge-to-edge technique. METHODS/MATERIALS: We simulated the treatment of a real long significant coronary lesion (>70% luminal narrowing) involving the left anterior descending artery (LAD) treated with a standard or edge-to-edge technique, respectively...
August 17, 2017: Cardiovascular Revascularization Medicine: Including Molecular Interventions
https://www.readbyqxmd.com/read/28917963/an-efficient-computational-fluid-particle-dynamics-method-to-predict-deposition-in-a-simplified-approximation-of-the-deep-lung
#11
P G Koullapis, P Hofemeier, J Sznitman, S C Kassinos
High-fidelity simulations of the complete airway tree are still largely beyond current computational capabilities. Towards large-scale simulations of the human lung, the current study introduces a numerical methodology to predict particle deposition in a simplified approximation of the deep lung during a full breathing cycle. The geometrical model employed consists of an idealised bronchial tree that represents generations 10 to 19 of the conducting zone and an heterogeneous acinar model created using a space-filling algorithm...
September 13, 2017: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/28917579/microcirculation-in-the-murine-liver-a-computational-fluid-dynamic-model-based-on-3d-reconstruction-from-in-vivo-microscopy
#12
Monica Piergiovanni, Elena Bianchi, Giada Capitani, Irene Li Piani, Lucia Ganzer, Luca G Guidotti, Matteo Iannacone, Gabriele Dubini
The liver is organized in hexagonal functional units - termed lobules - characterized by a rather peculiar blood microcirculation, due to the presence of a tangled network of capillaries - termed sinusoids. A better understanding of the hemodynamics that governs liver microcirculation is relevant to clinical and biological studies aimed at improving our management of liver diseases and transplantation. Herein, we built a CFD model of a 3D sinusoidal network, based on in vivo images of a physiological mouse liver obtained with a 2-photon microscope...
September 2, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28915736/communication-a-method-to-compute-the-transport-coefficient-of-pure-fluids-diffusing-through-planar-interfaces-from-equilibrium-molecular-dynamics-simulations
#13
Romain Vermorel, Fouad Oulebsir, Guillaume Galliero
The computation of diffusion coefficients in molecular systems ranks among the most useful applications of equilibrium molecular dynamics simulations. However, when dealing with the problem of fluid diffusion through vanishingly thin interfaces, classical techniques are not applicable. This is because the volume of space in which molecules diffuse is ill-defined. In such conditions, non-equilibrium techniques allow for the computation of transport coefficients per unit interface width, but their weak point lies in their inability to isolate the contribution of the different physical mechanisms prone to impact the flux of permeating molecules...
September 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28915730/adsorption-and-diffusion-of-fluids-in-defective-carbon-nanotubes-insights-from-molecular-simulations
#14
Benjamin J Bucior, German V Kolmakov, JoAnna M Male, Jinchen Liu, De-Li Chen, Prashant Kumar, J Karl Johnson
Single-walled carbon nanotubes (SWNTs) have been shown from both simulations and experiments to have remarkably low resistance to gas and liquid transport. This has been attributed to the remarkably smooth interior surface of pristine SWNTs. However, real SWNTs are known to have various defects that depend on the synthesis method and procedure used to activate the SWNTs. In this paper we study adsorption and transport properties of atomic and molecular gases and fluids in SWNTs having vacancy point defects...
September 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28905268/fluid-and-biomechanical-analysis-of-ascending-thoracic-aorta-aneurysm-with-concomitant-aortic-insufficiency
#15
F Condemi, S Campisi, M Viallon, T Troalen, G Xuexin, A J Barker, M Markl, P Croisille, O Trabelsi, C Cavinato, A Duprey, S Avril
We present a comprehensive and original framework for the biomechanical analysis of patients affected by ascending thoracic aorta aneurysm and aortic insufficiency. Our aim is to obtain crucial indications about the role played by deranged hemodynamics on the ATAAs risk of rupture. Computational fluid dynamics analysis was performed using patient-specific geometries and boundary conditions derived from 4D MRI. Blood flow helicity and wall shear stress descriptors were assessed. A bulge inflation test was carried out in vitro on the 4 ATAAs after surgical repair...
September 13, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28902523/functional-assessment-of-lesion-severity-without-using-the-pressure-wire-coronary-imaging-and-blood-flow-simulation
#16
Michail I Papafaklis, Michail C Mavrogiannis, Panagiotis K Siogkas, Lampros S Lakkas, Christos S Katsouras, Dimitrios I Fotiadis, Lampros K Michalis
Hemodynamic indices derived from measurements with the pressure wire (primarily fractional flow reserve [FFR]) have been established as a reliable tool for assessing coronary stenoses and improving clinical decision making. However, the use of the pressure wire constitutes a hurdle for the universal adoption of physiology-guided patient management. Technological advancements have enabled the large-scale application of blood flow simulation (computational fluid dynamics [CFD]) to medical imaging, thereby enabling the virtual assessment of coronary physiology...
September 19, 2017: Expert Review of Cardiovascular Therapy
https://www.readbyqxmd.com/read/28902139/autonomous-sensors-powered-by-energy-harvesting-from-von-karman-vortices-in-airflow
#17
Marco Demori, Marco Ferrari, Arianna Bonzanini, Pietro Poesio, Vittorio Ferrari
In this paper an energy harvesting system based on a piezoelectric converter to extract energy from airflow and use it to power battery-less sensors is presented. The converter is embedded as a part of a flexure beam that is put into vibrations by von Karman vortices detached from a bluff body placed upstream. The vortex street has been investigated by Computational Fluid Dynamics (CFD) simulations, aiming at assessing the vortex shedding frequency as a function of the flow velocity. From the simulation results the preferred positioning of the beam behind the bluff body has been derived...
September 13, 2017: Sensors
https://www.readbyqxmd.com/read/28900625/direct-assessment-of-wall-shear-stress-by-signal-intensity-gradient-from-time-of-flight-magnetic-resonance-angiography
#18
Kap-Soo Han, Sang Hyuk Lee, Han Uk Ryu, Se-Hyoung Park, Gyung-Ho Chung, Young I Cho, Seul-Ki Jeong
The aim of the study was to calculate the arterial wall signal intensity gradient (SIG) from time-of-flight MR angiography (TOF-MRA) and represent arterial wall shear stress. We developed a new algorithm that uses signal intensity (SI) of a TOF-MRA to directly calculate the signal intensity gradient (SIG). The results from our phantom study showed that the TOF-MRA SIG could be used to distinguish the magnitude of blood flow rate as high (mean SIG ± SD, 2.2 ± 0.4 SI/mm for 12.5 ± 2.3 L/min) and low (0...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28894833/ethmoidectomy-combined-with-superior-meatus-enlargement-increases-olfactory-airflow
#19
Hironobu Nishijima, Kenji Kondo, Tsutomu Nomura, Tatsuya Yamasoba
OBJECTIVES: The relationship between a particular surgical technique in endoscopic sinus surgery (ESS) and airflow changes in the post-operative olfactory region has not been assessed. The present study aimed to compare olfactory airflow after ESS between conventional ethmoidectomy and ethmoidectomy with superior meatus enlargement, using virtual ESS and computational fluid dynamics (CFD) analysis. STUDY DESIGN: Prospective computational study. MATERIALS AND METHODS: Nasal computed tomography images of four adult subjects were used to generate models of the nasal airway...
August 2017: Laryngoscope Investigative Otolaryngology
https://www.readbyqxmd.com/read/28894819/computational-modelling-of-cough-function-and-airway-penetrant-behavior-in-patients-with-disorders-of-laryngeal-function
#20
Bari Hoffman Ruddy, Don Nadun Kuruppumullage, Giselle Carnaby, Michael Crary, Jeffery Lehman, Olusegun J Ilegbusi
OBJECTIVE/HYPOTHESIS: Patients with laryngeal disorders often exhibit changes to cough function contributing to aspiration episodes. Two primary cough variables (peak cough flow: PCF and compression phase duration: CPD) were examined within a biomechanical model to determine their impact on characteristics that impact airway compromise. STUDY DESIGN: Computational study. METHODS: A Computational Fluid Dynamics (CFD) technique was used to simulate fluid flow within an upper airway model reconstructed from patient CT images...
February 2017: Laryngoscope Investigative Otolaryngology
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