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Computational fluid dynamics

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https://www.readbyqxmd.com/read/28228027/ab-initio-state-specific-n2-o-dissociation-and-exchange-modeling-for-molecular-simulations
#1
Han Luo, Marat Kulakhmetov, Alina Alexeenko
Quasi-classical trajectory (QCT) calculations are used in this work to calculate state-specific N2(X(1)Σ)+O((3)P)→2N((4)S)+O((3)P) dissociation and N2(X(1)Σ)+O((3)P)→NO(X(2)Π)+N((4)S) exchange cross sections and rates based on the 1(3)A″ and 1(3)A' ab initio potential energy surface by Gamallo et al. [J. Chem. Phys. 119, 2545-2556 (2003)]. The calculations consider translational energies up to 23 eV and temperatures between 1000 K and 20 000 K. Vibrational favoring is observed for dissociation reaction at the whole range of collision energies and for exchange reaction around the dissociation limit...
February 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28227253/does-the-degree-of-coarctation-of-the-aorta-influence-wall-shear-stress-focal-heterogeneity
#2
John Gounley, Rafeed Chaudhury, Madhurima Vardhan, Michael Driscoll, Girish Pathangey, Kevin Winarta, Justin Ryan, David Frakes, Amanda Randles, John Gounley, Rafeed Chaudhury, Madhurima Vardhan, Michael Driscoll, Girish Pathangey, Kevin Winarta, Justin Ryan, David Frakes, Amanda Randles, Justin Ryan, Rafeed Chaudhury, Girish Pathangey, Amanda Randles, David Frakes, Kevin Winarta, Michael Driscoll, John Gounley, Madhurima Vardhan
The development of atherosclerosis in the aorta is associated with low and oscillatory wall shear stress for normal patients. Moreover, localized differences in wall shear stress heterogeneity have been correlated with the presence of complex plaques in the descending aorta. While it is known that coarctation of the aorta can influence indices of wall shear stress, it is unclear how the degree of narrowing influences resulting patterns. We hypothesized that the degree of coarctation would have a strong influence on focal heterogeneity of wall shear stress...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28227223/bringing-hemodynamic-simulations-closer-to-the-clinics-a-cfd-prototype-study-for-intracranial-aneurysms
#3
Philipp Berg, Samuel Vos, Mathias Becker, Steffen Serowy, Thomas Redel, Gabor Janiga, Martin Skalej, Oliver Beuing, Philipp Berg, Samuel Vos, Mathias Becker, Steffen Serowy, Thomas Redel, Gabor Janiga, Martin Skalej, Oliver Beuing, Steffen Serowy, Martin Skalej, Oliver Beuing, Thomas Redel, Philipp Berg, Gabor Janiga, Mathias Becker
Computational Fluid Dynamics enables the investigation of patient-specific hemodynamics for rupture predictions and treatment support of intracranial aneurysms. However, due to numerous simplifications to decrease the computations effort, clinical applicability is limited until now. To overcome this situation a clinical research software prototype was tested that can be easily operated by attending physicians. In order to evaluate the accuracy of this prototype, four patient-specific intracranial aneurysms were investigated using four different spatial resolutions...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28227222/hemodynamic-effects-from-coil-distribution-with-realistic-coil-models-in-an-aneurysm
#4
Soichiro Fujimura, Hiroyuki Takao, Takashi Suzuki, Chihebeddine Dahmani, Hiroya Mamori, Makoto Yamamoto, Yuichi Murayama, Soichiro Fujimura, Hiroyuki Takao, Takashi Suzuki, Chihebeddine Dahmani, Hiroya Mamori, Makoto Yamamoto, Yuichi Murayama, Makoto Yamamoto, Hiroya Mamori, Soichiro Fujimura, Takashi Suzuki, Yuichi Murayama, Chihebeddine Dahmani, Hiroyuki Takao
Because of its minimal invasiveness, coil embolization has become a popular way to treat aneurysms. The main problem with this method, however, is the poor understanding of the hemodynamics in the aneurysm after coil embolization. To improve this situation, we used a finite element method and computational fluid dynamics to investigate how hemodynamic parameters depend on the spatial distribution of coils. A basic model of an internal carotid artery aneurysm was created, and six realistic coil models were considered for the coil geometry...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28227065/fea-modeling-and-fluid-flow-simulation-of-human-rectum-with-inserted-bowel-catheters
#5
Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman, Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman, Tina VanRiper, Drew Weidman, Brian Rague, Yong Zhang
In this project, fluid flow and fluid-structure interaction are studied for the human lower gastrointestinal (GI) region. The study consists of two steps. First, we apply meshing methods to discretize both the human lower GI model and the catheter model at sufficient resolution suitable for importing into a Finite Element Analysis (FEA) tool. For model discretization, 3D models of the colon reconstructed from human MRI slices are used to obtain the valid inlet and outlet boundary surfaces. To resolve the viscous boundary layer in flow studies, a special structure of the near-wall volumetric mesh is built by triangular prisms that construct quasi-structured, multiple near-boundary sub-layers...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28226721/overcoming-spatio-temporal-limitations-using-dynamically-scaled-in-vitro-pc-mri-a-flow-field-comparison-to-true-scale-computer-simulations-of-idealized-stented-and-patient-specific-left-main-bifurcations
#6
Susann Beier, John Ormiston, Mark Webster, John Cater, Stuart Norris, Pau Medrano-Gracia, Alistair Young, Kathleen Gilbert, Brett Cowan, Susann Beier, John Ormiston, Mark Webster, John Cater, Stuart Norris, Pau Medrano-Gracia, Alistair Young, Kathleen Gilbert, Brett Cowan, Stuart Norris, Brett Cowan, Pau Medrano-Gracia, Kathleen Gilbert, Mark Webster, Alistair Young, Susann Beier, John Cater, John Ormiston
The majority of patients with angina or heart failure have coronary artery disease. Left main bifurcations are particularly susceptible to pathological narrowing. Flow is a major factor of atheroma development, but limitations in imaging technology such as spatio-temporal resolution, signal-to-noise ratio (SNRv), and imaging artefacts prevent in vivo investigations. Computational fluid dynamics (CFD) modelling is a common numerical approach to study flow, but it requires a cautious and rigorous application for meaningful results...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28220273/numerical-and-experimental-investigations-of-the-flow-pressure-relation-in-multiple-sequential-stenoses-coronary-artery
#7
S Li, Cheng Chin, Vikas Thondapu, Eric K W Poon, Jason P Monty, Yingguang Li, Andrew S H Ooi, Shengxian Tu, Peter Barlis
Virtual fractional flow reserve (vFFR) has been evaluated as an adjunct to invasive fractional flow reserve (FFR) in the light of its operational and economic benefits. The accuracy of vFFR and the complexity of hyperemic flow simulation are still not clearly understood. This study investigates the flow-pressure relation in an idealised multiple sequential stenoses coronary artery model via numerical and experimental approaches. Pressure drop is linearly correlated with flow rate irrespective of the number of stenosis...
February 20, 2017: International Journal of Cardiovascular Imaging
https://www.readbyqxmd.com/read/28218279/multi-constituent-simulation-of-thrombus-deposition
#8
Wei-Tao Wu, Megan A Jamiolkowski, William R Wagner, Nadine Aubry, Mehrdad Massoudi, James F Antaki
In this paper, we present a spatio-temporal mathematical model for simulating the formation and growth of a thrombus. Blood is treated as a multi-constituent mixture comprised of a linear fluid phase and a thrombus (solid) phase. The transport and reactions of 10 chemical and biological species are incorporated using a system of coupled convection-reaction-diffusion (CRD) equations to represent three processes in thrombus formation: initiation, propagation and stabilization. Computational fluid dynamic (CFD) simulations using the libraries of OpenFOAM were performed for two illustrative benchmark problems: in vivo thrombus growth in an injured blood vessel and in vitro thrombus deposition in micro-channels (1...
February 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28211963/a-parametric-model-of-the-brain-vascular-system-for-estimation-of-the-arterial-input-function-aif-at-the-tissue-level
#9
Siamak P Nejad-Davarani, Hassan Bagher-Ebadian, James R Ewing, Douglas C Noll, Tom Mikkelsen, Michael Chopp, Quan Jiang
In this paper, we introduce a novel model of the brain vascular system, which is developed based on laws of fluid dynamics and vascular morphology. This model is used to address dispersion and delay of the arterial input function (AIF) at different levels of the vascular structure and to estimate the local AIF in DCE images. We developed a method based on the simplex algorithm and Akaike information criterion to estimate the likelihood of the contrast agent concentration signal sampled in DCE images belonging to different layers of the vascular tree or being a combination of different signal levels from different nodes of this structure...
February 17, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28210959/glass-transition-in-hard-core-fluids-and-beyond-using-an-effective-static-structure-in-the-mode-coupling-theory
#10
S Amokrane, F Tchangnwa Nya, J M Ndjaka
The dynamical arrest in classical fluids is studied using a simple modification of the mode coupling theory (MCT) aimed at correcting its overestimation of the tendency to glass formation while preserving its overall structure. As in previous attempts, the modification is based on the idea of tempering the static pair correlations used as input. It is implemented in this work by computing the static structure at a different state point than the one used to solve the MCT equation for the intermediate scattering function, using the pure hard-sphere glass for calibration...
February 2017: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/28209576/differences-in-hemodynamics-and-rupture-rate-of-aneurysms-at-the-bifurcation-of-the-basilar-and-internal-carotid-arteries
#11
R Doddasomayajula, B Chung, F Hamzei-Sichani, C M Putman, J R Cebral
BACKGROUND AND PURPOSE: Cerebral aneurysms in the posterior circulation are known to have a higher rupture risk than those in the anterior circulation. We sought to test the hypothesis that differences in hemodynamics can explain the difference in rupture rates. MATERIALS AND METHODS: A total of 117 aneurysms, 63 at the tip of the basilar artery (27 ruptured, 36 unruptured, rupture rate = 43%) and 54 at the bifurcation of the internal carotid artery (11 ruptured, 43 unruptured, rupture rate = 20%) were analyzed with image-based computational fluid dynamics...
February 16, 2017: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/28197271/low-density-lipoprotein-and-non-newtonian-oscillating-flow-biomechanical-parameters-for-normal-human-aorta
#12
Johannes V Soulis, Dimitrios K Fytanidis, Olga P Lampri, George D Giannoglou
BACKGROUND: The temporal variation of the hemodynamic mechanical parameters during cardiac pulse wave is considered as an important atherogenic factor. Applying non-Newtonian blood molecular viscosity simulation is crucial for hemodynamic analysis. Understanding low density lipoprotein (LDL) distribution in relation to flow parameters will possibly spot the prone to atherosclerosis aorta regions. METHODS: The biomechanical parameters tested were averaged wall shear stress (AWSS), oscillatory shear index (OSI) and relative residence time (RRT) in relation to the LDL concentration...
April 2016: Cardiology Research
https://www.readbyqxmd.com/read/28196148/from-the-track-to-the-ocean-using-flow-control-to-improve-marine-bio-logging-tags-for-cetaceans
#13
Giovani Fiore, Erik Anderson, C Spencer Garborg, Mark Murray, Mark Johnson, Michael J Moore, Laurens Howle, K Alex Shorter
Bio-logging tags are an important tool for the study of cetaceans, but superficial tags inevitably increase hydrodynamic loading. Substantial forces can be generated by tags on fast-swimming animals, potentially affecting behavior and energetics or promoting early tag removal. Streamlined forms have been used to reduce loading, but these designs can accelerate flow over the top of the tag. This non-axisymmetric flow results in large lift forces (normal to the animal) that become the dominant force component at high speeds...
2017: PloS One
https://www.readbyqxmd.com/read/28195732/in-vivo-predictive-dissolution-ipd-and-biopharmaceutical-modeling-and-simulation-future-use-of-modern-approaches-and-methodologies-in-a-regulatory-context
#14
H Lennernas, A Lindahl, A Van Peer, C Ollier, T Flanagan, R Lionberger, A Nordmark, S Yamashita, L Yu, G L Amidon, V Fischer, E Sjögren, P Zane, M McAllister, B Abrahamsson
The overall objective of OrBiTo, a project within Innovative Medicines Initiative (IMI), is to streamline and optimize the development of orally administered drug products through the creation and efficient application of biopharmaceutics tools. This toolkit will include both experimental and computational models developed on improved understanding of the highly dynamic gastrointestinal (GI) physiology relevant to the GI absorption of drug products in both fasted and fed states. A part of the annual OrBiTo-meeting in 2015 was dedicated to the presentation of the most recent progress in the development of the regulatory use of PBPK in silico modeling, in vivo predictive dissolution (IPD) tests and their application to biowaivers...
February 14, 2017: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/28195288/slip-divergence-of-water-flow-in-graphene-nanochannels-the-role-of-chirality
#15
Enrique Wagemann, Elton Oyarzua, Jens H Walther, Harvey A Zambrano
Graphene has attracted considerable attention due to its characteristics as a 2D material and its fascinating properties, providing a potential building block for nanofabrication. In nanochannels the solid-liquid interface plays a non-negligible role in determining the fluid dynamics. Therefore, for an optimal design of nanofluidic devices, a comprehensive understanding of the slippage in a water flow confined between graphene walls is important. In nanoconfinement, experimental and computational studies have found the slip length to increase nonlinearly when the shear rate is larger than a critical value...
February 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28190607/patient-specific-assessment-of-hemodynamics-by-computational-fluid-dynamics-in-patients-with-bicuspid-aortopathy
#16
Naoyuki Kimura, Masanori Nakamura, Kenji Komiya, Satoshi Nishi, Atsushi Yamaguchi, Osamu Tanaka, Yoshio Misawa, Hideo Adachi, Koji Kawahito
OBJECTIVE: Hemodynamics related to eccentric blood flow may factor into the development of bicuspid aortic valve aortopathy. We investigated wall shear stress distribution by means of magnetic resonance imaging-based computational fluid dynamics in patients with a bicuspid aortic valve. METHODS: Included were 12 patients with a bicuspid aortic valve (aortic stenosis, n = 11; root enlargement, n = 1). Three patients with a normal tricuspid aortic valve (arch aneurysm, n = 1; descending aortic aneurysm, n = 2) were included for comparison...
January 11, 2017: Journal of Thoracic and Cardiovascular Surgery
https://www.readbyqxmd.com/read/28186882/multi-modality-imaging-enables-detailed-hemodynamic-simulations-in-dissecting-aneurysms-in-mice
#17
Evan Phillips, Paolo Di Achille, Matthew Bersi, Jay Humphrey, Craig Goergen
A multi-modality imaging based modeling approach was used to study complex unsteady hemodynamics and lesion growth in a dissecting abdominal aortic aneurysm model. We combined in vivo ultrasound (geometry and flow) and in vitro optical coherence tomography (geometry) to obtain the high resolution needed to construct detailed hemodynamic simulations over large portions of the murine vasculature, which include fine geometric complexities. We illustrate this approach for a spectrum of dissecting abdominal aortic aneurysms induced in male apolipoprotein E-null mice by high-dose angiotensin II infusion...
February 6, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28186879/fluid-dynamic-models-for-bhattacharyya-based-discriminant-analysis
#18
Yung-Kyun Noh, Jihun Hamm, Frank Park, Byoung-Tak Zhang, Daniel D Lee
Classical discriminant analysis attempts to discover a low-dimensional subspace where class label information is maximally preserved under projection. Canonical methods for estimating the subspace optimize an information-theoretic criterion that measures the separation between the class-conditional distributions. Unfortunately, direct optimization of the information-theoretic criteria is generally non-convex and intractable in high-dimensional spaces. In this work, we propose a novel, tractable algorithm for discriminant analysis that considers the class-conditional densities as interacting fluids in the high-dimensional embedding space...
February 8, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
https://www.readbyqxmd.com/read/28186231/computational-fluid-dynamics-in-aortic-arch-pathophysiology
#19
Saeed Ranjbar, Peyman Sardari Nia, Mersedeh Karvandi, Jos Maessen
No abstract text is available yet for this article.
February 1, 2017: European Journal of Cardio-thoracic Surgery
https://www.readbyqxmd.com/read/28181817/mathematical-modeling-of-intraperitoneal-drug-delivery-simulation-of-drug-distribution-in-a-single-tumor-nodule
#20
Margo Steuperaert, Giuseppe Falvo D'Urso Labate, Charlotte Debbaut, Olivier De Wever, Christian Vanhove, Wim Ceelen, Patrick Segers
The intraperitoneal (IP) administration of chemotherapy is an alternative treatment for peritoneal carcinomatosis, allowing for higher intratumor concentrations of the cytotoxic agent compared to intravenous administration. Nevertheless, drug penetration depths are still limited to a few millimeters. It is thus necessary to better understand the limiting factors behind this poor penetration in order to improve IP chemotherapy delivery. By developing a three-dimensional computational fluid dynamics (CFD) model for drug penetration in a tumor nodule, we investigated the impact of a number of key parameters on the drug transport and penetration depth during IP chemotherapy...
November 2017: Drug Delivery
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