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Computational fluid dynamics

Maurice Filo, Fadi Karameh, Mariette Awad
The cochlea is an indispensable preliminary processing stage in auditory perception that employs mechanical frequency-tuning and electrical transduction of incoming sound waves. Cochlear mechanical responses are shown to exhibit active nonlinear spatiotemporal response dynamics (e.g., otoacoustic emission). To model such phenomena, it is often necessary to incorporate cochlear fluid-membrane interactions. This results in both excessively high-order model formulations and computationally intensive solutions that limit their practical use in simulating the model and analyzing its response even for simple single-tone inputs...
October 17, 2016: Biological Cybernetics
Liu Chunbao, Li Li, Lei Yulong, Liu Changsuo, Zhang Yubo
Fish-like, dolphin-like, and bionic nonsmooth surfaces were employed in a hydraulic torque converter to achieve drag reduction and performance improvement, which were aimed at reducing profile loss, impacting loss and friction loss, respectively. YJSW335, a twin turbine torque converter, was bionically designed delicately. The biological characteristics consisted of fish-like blades in all four wheels, dolphin-like structure in the first turbine and the stator, and nonsmooth surfaces in the pump. The prediction performance of bionic YJSW335, obtained by computational fluid dynamics simulation, was improved compared with that of the original model, and then it could be proved that drag reduction had been achieved...
2016: Applied Bionics and Biomechanics
Jenny M Pedersen, Yoo-Sik Shim, Vaibhav Hans, Martin B Phillips, Jeffrey M Macdonald, Glenn Walker, Melvin E Andersen, Harvey J Clewell, Miyoung Yoon
Accurate prediction of metabolism is a significant outstanding challenge in toxicology. The best predictions are based on experimental data from in vitro systems using primary hepatocytes. The predictivity of the primary hepatocyte-based culture systems, however, is still limited due to well-known phenotypic instability and rapid decline of metabolic competence within a few hours. Dynamic flow bioreactors for three-dimensional cell cultures are thought to be better at recapitulating tissue microenvironments and show potential to improve in vivo extrapolations of chemical or drug toxicity based on in vitro test results...
2016: Frontiers in Bioengineering and Biotechnology
Ruofei Bu, Hillel Price, Sorin Mitran, Carlton Zdanski, Amy L Oldenburg
Quantitative endoscopic imaging is at the vanguard of novel techniques in the assessment upper airway obstruction. Anatomic optical coherence tomography (aOCT) has the potential to provide the geometry of the airway lumen with high-resolution and in 4 dimensions. By coupling aOCT with measurements of pressure, optical coherence elastography (OCE) can be performed to characterize airway wall stiffness. This can aid in identifying regions of dynamic collapse as well as informing computational fluid dynamics modeling to aid in surgical decision-making...
2016: Proceedings of SPIE
Jianke Huang, Jiangguo Ying, Fei Fan, Qijian Yang, Jun Wang, Yuanguang Li
Aiming to culture algae with high efficiency, a novel vertical multi-column airlift photobioreactor (VMAPBR) has been developed. It was constructed with a series of vertically arranged parallel columns with easy scalability. The hydrodynamic, irradiation and shear stress characteristics of the photobioreactor were studied by computational fluid dynamics (CFD). Accordingly, the optimal aeration manner and aeration rate were determined. When the novel airlift PBR was alternately aerated with aeration rate of 0...
September 29, 2016: Bioresource Technology
Keizo Yamamoto, Makoto Tsubokura, Jun Ikeda, Keiji Onishi, Sophie Baleriola
The purpose of this study was to investigate the effects of posture of a ski jumper on aerodynamic characteristics during the take-off using computational fluid dynamics (CFD). The CFD method adopted for this study was based on Large-Eddy Simulation. Body surface data were obtained by 3-D laser scanning of an active ski jumper. Based on video analysis of the actual take-off movement, two sets of motion data were generated (world-class jumper A and less-experienced jumper B). The inlet flow velocity that corresponds to the in-run velocity in actual ski jumping was set to 23...
October 6, 2016: Journal of Biomechanics
Eric Lauga, Sébastien Michelin
Active particles disturb the fluid around them as force dipoles, or stresslets, which govern their collective dynamics. Unlike swimming speeds, the stresslets of active particles are rarely determined due to the lack of a suitable theoretical framework for arbitrary geometry. We propose a general method, based on the reciprocal theorem of Stokes flows, to compute stresslets as integrals of the velocities on the particle's surface, which we illustrate for spheroidal chemically active particles. Our method will allow tuning the stresslet of artificial swimmers and tailoring their collective motion in complex environments...
September 30, 2016: Physical Review Letters
Jorge Rey-Martinez, Leigh McGarvie, Nicolás Pérez-Fernández
CONCLUSION: The obtained simulations support the underlying hypothesis that the hydrostatic caloric drive is dissipated by local convective flow in a hydropic duct. OBJECTIVE: To develop a computerized model to simulate and predict the internal fluid thermodynamic behavior within both normal and hydropic horizontal ducts. METHODS: This study used a computational fluid dynamics software to simulate the effects of cooling and warming of two geometrical models representing normal and hydropic ducts of one semicircular horizontal canal during 120 s...
October 14, 2016: Acta Oto-laryngologica
Wolfgang Wiedemair, Zeljko Tukovic, Hrvoje Jasak, Dimos Poulikakos, Vartan Kurtcuoglu
Encapsulated microbubbles (MBs) serve as endovascular agents in a wide range of medical ultrasound applications. The oscillatory response of these agents to ultrasonic excitation is determined by MB size, gas content, viscoelastic shell properties and geometrical constraints. The viscoelastic parameters of the MB capsule vary during an oscillation cycle and change irreversibly upon shell rupture. The latter results in marked stress changes on the endothelium of capillary blood vessels due to altered MB dynamics...
October 12, 2016: Biomechanics and Modeling in Mechanobiology
F Economou, S Katranas, G Giannoglou, K Gemitzis, I Styliadis, G Efthimiadis, H Karvounis, A Ziakas
BACKGROUND: Endothelial shear stress (ESS) may play a key role in the pathobiology of stent restenosis (SR). Nevertheless, limited data are available about ESS and its relation to SR. PATIENTS AND METHODS: We enrolled 14 patients who underwent successful percutaneous coronary intervention (PCI) in this study. Three-dimensional (3D) reconstruction of 14 coronary arteries before and after stent implantation was performed. Using computational fluid dynamics, mean ESS was calculated proximally, in tertiles within and distal to the stent, both before and after stent implantation...
October 12, 2016: Herz
Andrew Abboud, Qi Mi, Ava Puccio, David Okonkwo, Marius Buliga, Gregory Constantine, Yoram Vodovotz
Inflammation induced by traumatic brain injury (TBI) is a complex mediator of morbidity and mortality. We have previously demonstrated the utility of both data-driven and mechanistic models in settings of traumatic injury. We hypothesized that differential dynamic inflammation programs characterize TBI survivors vs. non-survivors, and sought to leverage computational modeling to derive novel insights into this life/death bifurcation. Thirteen inflammatory cytokines and chemokines were determined using Luminex™ in serial cerebrospinal fluid (CSF) samples from 31 TBI patients over 5 days...
2016: Frontiers in Pharmacology
Jorge R Espinosa, Pablo Sampedro, Chantal Valeriani, Carlos Vega, Eduardo Sanz
We present a new simulation method for the calculation of crystal nucleation rates by computer simulation. The method is based on the use of molds to induce crystallization in state points where nucleation is a rare event. The mold is a cluster of potential energy wells placed in the lattice positions of the solid. The method has two distinct steps. In the first one the probability per unit volume of forming a sub-critical crystal cluster in the fluid is computed by means of thermodynamic integration. The thermodynamic route consists in gradually switching on an attractive interaction between the wells and the fluid particles...
October 11, 2016: Faraday Discussions
Karen-Helene Støverud, Hans Petter Langtangen, Geir Andre Ringstad, Per Kristian Eide, Kent-Andre Mardal
PURPOSE: Previous computational fluid dynamics (CFD) studies have demonstrated that the Chiari malformation is associated with abnormal cerebrospinal fluid (CSF) flow in the cervical part of the subarachnoid space (SAS), but the flow in the SAS of the posterior cranial fossa has received little attention. This study extends previous modelling efforts by including the cerebellomedullary cistern, pontine cistern, and 4th ventricle in addition to the cervical subarachnoid space. METHODS: The study included one healthy control, Con1, and two patients with Chiari I malformation, P1 and P2...
2016: PloS One
Xingli Liu, Weiwei Yan, Yang Liu, Yat Sze Choy, Yikun Wei
The flow characteristics in the realistic human upper airway (HUA) with obstruction that resulted from pharyngeal collapse were numerically investigated. The 3D anatomically accurate HUA model was reconstructed from CT-scan images of a Chinese male patient (38 years, BMI 25.7). The computational fluid dynamics (CFD) with the large eddy simulation (LES) method was applied to simulate the airflow dynamics within the HUA model in both inspiration and expiration processes. The laser Doppler anemometry (LDA) technique was simultaneously adopted to measure the airflow fields in the HUA model for the purpose of testifying the reliability of LES approach...
2016: Computational and Mathematical Methods in Medicine
Hung-Yi Lai, Ching-Hsin Lee, Ching-Yi Lee
BACKGROUND: For patients suffering from primary brain injury, monitoring intracranial pressure alone is not enough to reflect the dynamic intracranial condition. In our previous study, a segment of the pressure-volume curve can be expressed by the parabolic regression model with single indicator "a". The aim of this study is to evaluate if the indicator "a" can reflect intracranial conditions. METHODS: Patients with traumatic brain injury, spontaneous intracranial hemorrhage, and/or hydrocephalus who had external ventricular drainage from January 2009 to February 2010 were included...
2016: PloS One
Hamed Moradkhani, Mir-Shahabeddin Izadkhah, Navideh Anarjan
In this work, gas dispersion in a two-phase partitioning bioreactor is analyzed by calculating volumetric oxygen mass transfer coefficient which is modeled using a commercial computational fluid dynamics (CFD), code FLUENT 6.2. Dispersed oxygen bubbles dynamics is based on standard "k-ε" Reynolds-averaged Navier-Stokes (RANS) model. This paper describes a three-dimensional CFD model coupled with population balance equations (PBE) in order to get more confirming results of experimental measurements. Values of k L a are obtained using dynamic gassing-out method...
October 8, 2016: Applied Biochemistry and Biotechnology
S Voß, S Glaßer, T Hoffmann, O Beuing, S Weigand, K Jachau, B Preim, D Thévenin, G Janiga, P Berg
Computational Fluid Dynamics is intensively used to deepen the understanding of aneurysm growth and rupture in order to support physicians during therapy planning. However, numerous studies considering only the hemodynamics within the vessel lumen found no satisfactory criteria for rupture risk assessment. To improve available simulation models, the rigid vessel wall assumption has been discarded in this work and patient-specific wall thickness is considered within the simulation. For this purpose, a ruptured intracranial aneurysm was prepared ex vivo, followed by the acquisition of local wall thickness using μCT...
2016: Computational and Mathematical Methods in Medicine
K Ashoke Raman, Rajeev K Jaiman, Thong-See Lee, Hong-Tong Low
Three dimensional simulations are performed to investigate the interaction dynamics between two drops impinging simultaneously on a dry surface. Of particular interest in this study is to understand the effects of impact velocity and surrounding gas density on droplet interactions. To simulate the droplet dynamics and morphologies, a computational framework based on the phase-field lattice Boltzmann formulation is employed for the two-phase flow computations involving high density ratio. Two different coalescence modes are identified when the impinging droplets have different impact speeds...
October 1, 2016: Journal of Colloid and Interface Science
Chubin Ou, Wei Huang, Matthew Ming-Fai Yuen, Yi Qian
Hemodynamics has been recognized as an important factor in the development, growth, and rupture of cerebral aneurysms, and investigated by computational fluid dynamics techniques using a single phase approach. However, flow-dependent cell transport and interactions are usually ignored in single phase models, in which blood is usually treated as a single phase Newtonian fluid. For getting better insight into the underlying pathology of intracranial aneurysm, cell transport and interactions should be covered in hemodynamic studies...
September 16, 2016: Journal of Biomechanics
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