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Computational fluid dynamics

M Xu, M R Paul
We explore the spatiotemporal dynamics of the spectrum of covariant Lyapunov vectors for chaotic Rayleigh-Bénard convection. We use the inverse participation ratio to quantify the amount of spatial localization of the covariant Lyapunov vectors. The covariant Lyapunov vectors are found to be spatially localized at times when the instantaneous covariant Lyapunov exponents are large. The spatial localization of the Lyapunov vectors often occurs near defect structures in the fluid flow field. There is an overall trend of decreasing spatial localization of the Lyapunov vectors with increasing index of the vector...
March 2018: Physical Review. E
Antonello A Barresi, Valeria Rasetto, Daniele L Marchisio
This manuscript shows how computational models, mainly based on Computational Fluid Dynamics (CFD), can be used to simulate different parts of an industrial freeze-drying equipment and to properly design them; in particular, the freeze-dryer chamber and the duct connecting the chamber with the condenser, with the valves and vanes eventually present are analysed in this work. In Part 1, it will be shown how CFD can be employed to improve specific designs, to perform geometry optimization, to evaluate different design choices and how it is useful to evaluate the effect on product drying and batch variance...
May 15, 2018: European Journal of Pharmaceutics and Biopharmaceutics
Siddhartha Moulik, Vani Bukke, S Chandrasekhar Sajja, Sridhar S
Present work reports the synthesis of a novel Chitosan-Polytetrafluoroethylene composite membrane with solvent resistant property for efficient separation of methanol/toluene mixture by pervaporation. The composite was crossed with tetraethyl orthosilicate (TEOS) to prevent or reduce membrane swelling and improve the separation factor. The synthesized membranes were characterized by SEM, FTIR and DSC analysis. Molecular dynamics (MD) simulation and computational fluid dynamics were coupled to predict the structural and diffusive properties besides concentration profile inside the membrane...
August 1, 2018: Carbohydrate Polymers
Homa Naseri, Kieran Trickett, Nicholas Mitroglou, Ioannis Karathanassis, Phoevos Koukouvinis, Manolis Gavaises, Robert Barbour, Dale Diamond, Sarah E Rogers, Maurizio Santini, Jin Wang
We identify the physical mechanism through which newly developed quaternary ammonium salt (QAS) deposit control additives (DCAs) affect the rheological properties of cavitating turbulent flows, resulting in an increase in the volumetric efficiency of clean injectors fuelled with diesel or biodiesel fuels. Quaternary ammonium surfactants with appropriate counterions can be very effective in reducing the turbulent drag in aqueous solutions, however, less is known about the effect of such surfactants in oil-based solvents or in cavitating flow conditions...
May 16, 2018: Scientific Reports
Mahboubeh Jafarkhani, Zeinab Salehi, Reza Kowsari-Esfahan, Mohammad Ali Shokrgozar, M Rezaa Mohammadi, Jayakumar Rajadas, Masoud Mozafari
The increasing population of patients with heart disease and the limited availability of organs for transplantation have encouraged multiple strategies to fabricate healthy implantable cardiac tissues. One of the main challenges in cardiac tissue engineering is to direct cell behaviors to form functional three-dimensional (3D) biomimetic constructs. This article provides a brief review on various cell sources used in cardiac tissue engineering and highlights the effect of scaffold-based signals such as topographical and biochemical cues and stiffness...
May 16, 2018: Biomaterials Science
Ioannis Skarmoutsos, Mohamed Eddaoudi, Guillaume Maurin
Force field based-Molecular dynamics simulations were deployed to systematically explore the dynamics of confined molecules of different shapes and sizes, i.e. linear (CO2 and N2) and spherical (CH4) fluids, in a model small pore system, i.e. the Metal-Organic Framework SIFSIX-2-Cu-i. These computations unveil an unprecedented molecular symmetry dependence of the translational and rotational dynamics of fluids confined in channel-like nanoporous materials. In particular this peculiar behaviour is reflected by the extremely slow decay of the Legendre reorientational correlation functions of even-parity order for the linear fluids which is associated to jump-like orientation flips, while the spherical fluid shows a very fast decay taking place in a sub-picosecond time scale...
May 15, 2018: Journal of Physical Chemistry Letters
S Samaneh Lashkarinia, Senol Piskin, Tijen A Bozkaya, Ece Salihoglu, Can Yerebakan, Kerem Pekkan
Surgical treatment of congenital heart disease (CHD) involves complex vascular reconstructions utilizing artificial and native surgical materials. A successful surgical reconstruction achieves an optimal hemodynamic profile through the graft in spite of the complex post-operative vessel growth pattern and the altered pressure loading. This paper proposes a new in silico patient-specific pre-surgical planning framework for patch reconstruction and investigates its computational feasibility. The proposed protocol is applied to the patch repair of main pulmonary artery (MPA) stenosis in the Tetralogy of Fallot CHD template...
May 14, 2018: Annals of Biomedical Engineering
Federica Sacco, Bruno Paun, Oriol Lehmkuhl, Tinen L Iles, Paul A Iaizzo, Guillaume Houzeaux, Mariano Vázquez, Constantine Butakoff, Jazmin Aguado-Sierra
The aim of the present study is to characterize the hemodynamics of left ventricular (LV) geometries to examine the impact of trabeculae and papillary muscles (PMs) on blood flow using high performance computing (HPC). Five pairs of detailed and smoothed LV endocardium models were reconstructed from high-resolution magnetic resonance images (MRI) of ex-vivo human hearts. The detailed model of one LV pair is characterized only by the PMs and few big trabeculae, to represent state of art level of endocardial detail...
2018: Frontiers in Physiology
Mirko Bonfanti, Stavroula Balabani, Mona Alimohammadi, Obiekezie Agu, Shervanthi Homer-Vanniasinkam, Vanessa Díaz-Zuccarini
Aortic dissection (AD) is a complex and highly patient-specific vascular condition difficult to treat. Computational fluid dynamics (CFD) can aid the medical management of this pathology, yet its modelling and simulation are challenging. One aspect usually disregarded when modelling AD is the motion of the vessel wall, which has been shown to significantly impact simulation results. Fluid-structure interaction (FSI) methods are difficult to implement and are subject to assumptions regarding the mechanical properties of the vessel wall, which cannot be retrieved non-invasively...
May 11, 2018: Medical Engineering & Physics
Chenyuan Sha, Xuemei Wang, Yuanyuan Lin, Yifan Fan, Xi Chen, Jian Hang
Sustainable urban design is an effective way to improve urban ventilation and reduce vehicular pollutant exposure to urban residents. This paper investigated the impacts of urban open space and 'lift-up' building design on vehicular CO (carbon monoxide) exposure in typical three-dimensional (3D) urban canopy layer (UCL) models under neutral atmospheric conditions. The building intake fraction (IF) represents the fraction of total vehicular pollutant emissions inhaled by residents when they stay at home. The building daily CO exposure (Et ) means the extent of human beings' contact with CO within one day indoor at home...
August 15, 2018: Science of the Total Environment
Manash Pratim Borthakur, Gautam Biswas, Dipankar Bandyopadhyay
A computational fluid dynamic investigation has been carried out to study the dynamics of a moving compound droplet inside a tube. The motions associated with such a droplet is uncovered by solving the axisymmetric Navier-Stokes equations in which the spatiotemporal evolution of a pair of twin-deformable interfaces has been tracked employing the volume-of-fluid approach. The deformations at the interfaces and their subsequent dynamics are found to be stimulated by the subtle interplay between the capillary and viscous forces...
April 2018: Physical Review. E
Lauren Eichaker, Chengyu Li, Nakesha King, Victoria Pepper, Cameron Best, Ekene Onwuka, Eric Heuer, Kai Zhao, Jonathan Grischkan, Christopher Breuer, Jed Johnson, Tendy Chiang
OBJECTIVES/HYPOTHESIS: Current techniques for airway characterization include endoscopic or radiographic measurements that produce static, two-dimensional descriptions. As pathology can be multilevel, irregularly shaped, and dynamic, minimal luminal area (MLA) may not provide the most comprehensive description or diagnostic metric. Our aim was to examine the utilization of computational fluid dynamics (CFD) for the purpose of defining airway stenosis using an ovine model of tissue-engineered tracheal graft (TETG) implantation...
May 14, 2018: Laryngoscope
Ji Wook Choi, Jong Min Lee, Tae Hyun Kim, Jang Ho Ha, Christian D Ahrberg, Bong Geun Chung
The droplet-generating microfluidics has become an important technique for a variety of applications ranging from single cell analysis to nanoparticle synthesis. Although there are a large number of methods for generating and experimenting with droplets on microfluidic devices, the dispensing of droplets from these microfluidic devices is a challenge due to aggregation and merging of droplets at the interface of microfluidic devices. Here, we present a microfluidic dual-nozzle device for the generation and dispensing of uniform-sized droplets...
2018: Nano Convergence
Fang Wang, Yong Han, Bingyu Wang, Qian Peng, Xiaoqun Huang, Karol Miller, Adam Wittek
In this study, we investigate the effects of modelling choices for the brain-skull interface (layers of tissues between the brain and skull that determine boundary conditions for the brain) and the constitutive model of brain parenchyma on the brain responses under violent impact as predicted using computational biomechanics model. We used the head/brain model from Total HUman Model for Safety (THUMS)-extensively validated finite element model of the human body that has been applied in numerous injury biomechanics studies...
May 12, 2018: Biomechanics and Modeling in Mechanobiology
Everton Lucas-Oliveira, Arthur G Araujo-Ferreira, Willian A Trevizan, Carlos A Fortulan, Tito J Bonagamba
Nowadays, most of the efforts in NMR applied to porous media are dedicated to studying the molecular fluid dynamics within and among the pores. These analyses have a higher complexity due to morphology and chemical composition of rocks, besides dynamic effects as restricted diffusion, diffusional coupling, and exchange processes. Since the translational nuclear spin diffusion in a confined geometry (e.g. pores and fractures) requires specific boundary conditions, the theoretical solutions are restricted to some special problems and, in many cases, computational methods are required...
May 4, 2018: Journal of Magnetic Resonance
Gerasimos Siasos, Jaskanwal D Sara, Marina Zaromytidou, Kyoung H Park, Ahmet Umit Coskun, Lilach O Lerman, Evangelos Oikonomou, Charles C Maynard, Dimitris Fotiadis, Kostas Stefanou, Michail Papafaklis, Lampros Michalis, Charles Feldman, Amir Lerman, Peter H Stone
BACKGROUND: Local hemodynamic factors are important determinants of atherosclerotic plaque development and progression. OBJECTIVES: The goal of this study was to determine the association between low endothelial shear stress (ESS) and microvascular and epicardial endothelial dysfunction in patients with early atherosclerosis. METHODS: Sixty-five patients (mean age 52 ± 11 years) with nonobstructive coronary atherosclerosis (luminal diameter stenosis <30%) were included...
May 15, 2018: Journal of the American College of Cardiology
Miguel O Bernabeu, Martin L Jones, Rupert W Nash, Anna Pezzarossa, Peter V Coveney, Holger Gerhardt, Claudio A Franco
In this article, we present PolNet, an open-source software tool for the study of blood flow and cell-level biological activity during vessel morphogenesis. We provide an image acquisition, segmentation, and analysis protocol to quantify endothelial cell polarity in entire in vivo vascular networks. In combination, we use computational fluid dynamics to characterize the hemodynamics of the vascular networks under study. The tool enables, to our knowledge for the first time, a network-level analysis of polarity and flow for individual endothelial cells...
May 8, 2018: Biophysical Journal
Daniele L Marchisio, Miquel Galan, Antonello A Barresi
This manuscript shows how computational models, mainly based on Computational Fluid Dynamics (CFD), can be used to simulate different parts of an industrial freeze-drying equipment and to properly design them; in particular in this part the duct connecting the chamber with the condenser, with its valves, is considered, while the chamber design and its effect on drying kinetics have been investigated in Part 1. Such an approach allows a much deeper process understanding and assessment of the critical aspects of lyophilisation...
May 5, 2018: European Journal of Pharmaceutics and Biopharmaceutics
Jonas Jensen, Carlos Armando Villagómez Hoyos, Marie Sand Traberg, Jacob Bjerring Olesen, Borislav Gueorguiev Tomov, Ramin Moshavegh, Simon Holbek, Matthias Bo Stuart, Caroline Ewertsen, Kristoffer Lindskov Hansen, Carsten Thomsen, Michael Bachmann Nielsen, Jørgen Arendt Jensen
The objective of the study described here was to investigate the accuracy and precision of a plane wave 2-D vector flow imaging (VFI) method in laminar and complex blood flow conditions in the healthy carotid artery. The approach was to study (i) the accuracy for complex flow by comparing the velocity field from a computational fluid dynamics (CFD) simulation to VFI estimates obtained from the scan of an anthropomorphic flow phantom and from an in vivo scan; (ii) the accuracy for laminar unidirectional flow in vivo by comparing peak systolic velocities from VFI with magnetic resonance angiography (MRA); (iii) the precision of VFI estimation in vivo at several evaluation points in the vessels...
May 4, 2018: Ultrasound in Medicine & Biology
Michael C H Wu, Rana Zakerzadeh, David Kamensky, Josef Kiendl, Michael S Sacks, Ming-Chen Hsu
This paper considers an anisotropic hyperelastic soft tissue model, originally proposed for native valve tissue and referred to herein as the Lee-Sacks model, in an isogeometric thin shell analysis framework that can be readily combined with immersogeometric fluid-structure interaction (FSI) analysis for high-fidelity simulations of bioprosthetic heart valves (BHVs) interacting with blood flow. We find that the Lee-Sacks model is well-suited to reproduce the anisotropic stress-strain behavior of the cross-linked bovine pericardial tissues that are commonly used in BHVs...
April 12, 2018: Journal of Biomechanics
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