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Computational fluid dynamics

Alessandro Mauro, Nicola Massarotti, Mohamed Salahudeen, Mario R Romano, Vito Romano, Perumal Nithiarasu
The present work describes the application of the generalised porous medium model to study heat and fluid flow in healthy and glaucomatous eyes of different subject specimens, considering the presence of ocular cavities and porous tissues. The 2D computational model, implemented into the open-source software OpenFOAM, has been verified against benchmark data for mixed convection in domains partially filled with a porous medium. The verified model has been employed to simulate the thermo-fluid dynamic phenomena occurring in the anterior section of four patient-specific human eyes, considering the presence of anterior chamber (AC), trabecular meshwork (TM), Schlemm's canal (SC), and collector channels (CC)...
March 22, 2018: Medical & Biological Engineering & Computing
Francesco Fornarelli, Ruggiero Dadduzio, Marco Torresi, Sergio Mario Camporeale, Bernardo Fortunato
A fully 3D unsteady Computational Fluid Dynamics (CFD) approach coupled with heterogeneous reaction chemistry is presented in order to study the behavior of a single square channel as part of a Lean [Formula: see text] Traps. The reliability of the numerical tool has been validated against literature data considering only active BaO site. Even though the input/output performance of such catalyst has been well known, here the spatial distribution within a single channel is investigated in details. The square channel geometry influences the flow field and the catalyst performance being the flow velocity distribution on the cross section non homogeneous...
February 2018: Heliyon
Youyu Zhu, Feng Wang, Xuefei Deng
BACKGROUND: The physiological and hemodynamic features of bridging veins involve wall shear stress (WSS) of the cerebral venous system. Based on the data of cadavers and computational fluid dynamics software pack, the hemodynamic physical models of bridging veins (BVs) connecting superior sagittal sinus (SSS) were established. RESULTS: A total of 137 BVs formed two clusters along the SSS: anterior group and posterior group. The diameters of the BVs in posterior group were larger than of the anterior group, and the entry angle was smaller...
March 20, 2018: Biomedical Engineering Online
A Gupta, H J H Clercx, F Toschi
Particle-laden turbulent flows occur in a variety of industrial applications as well as in naturally occurring flows. While the numerical simulation of such flows has seen significant advances in recent years, it still remains a challenging problem. Many studies investigated the rheology of dense suspensions in laminar flows as well as the dynamics of point-particles in turbulence. Here we employ a fully-resolved numerical simulation based on a lattice Boltzmann scheme, to investigate turbulent flow with large neutrally buoyant particles in a pipe flow at low Reynolds number and in dilute regimes...
March 21, 2018: European Physical Journal. E, Soft Matter
L G Margolin
The applicability of Navier-Stokes equations is limited to near-equilibrium flows in which the gradients of density, velocity and energy are small. Here I propose an extension of the Chapman-Enskog approximation in which the velocity probability distribution function (PDF) is averaged in the coordinate phase space as well as the velocity phase space. I derive a PDF that depends on the gradients and represents a first-order generalization of local thermodynamic equilibrium. I then integrate this PDF to derive a hydrodynamic model...
April 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Theodorus M van Bakel, Christopher J Arthurs, Joost A van Herwaarden, Frans L Moll, Kim A Eagle, Himanshu J Patel, Santi Trimarchi, C Alberto Figueroa
OBJECTIVES: Aortic arch repair remains a major surgical challenge. Multiple manufacturers are developing branched endografts for Zone 0 endovascular repair, extending the armamentarium for minimally invasive treatment of aortic arch pathologies. We hypothesize that the design of the Zone 0 endograft has a significant impact on the postoperative haemodynamic performance, particularly in the cervical arteries. The goal of our study was to compare the postoperative haemodynamic performance of different Zone 0 endograft designs...
March 15, 2018: European Journal of Cardio-thoracic Surgery
Kenneth B Bader
Histotripsy is a form of therapeutic ultrasound that liquefies tissue mechanically via acoustic cavitation. Bubble expansion is paramount in the efficacy of histotripsy therapy, and the cavitation dynamics are strongly influenced by the medium elasticity. In this study, an analytic model to predict histotripsy-induced bubble expansion in a fluid was extended to include the effects of medium elasticity. Good agreement was observed between the predictions of the analytic model and numerical computations utilizing highly nonlinear excitations (shock-scattering histotripsy) and purely tensile pulses (microtripsy)...
March 19, 2018: Physics in Medicine and Biology
Jungeun Won, Guillermo L Monroy, Pin-Chieh Huang, Roshan Dsouza, Malcolm C Hill, Michael A Novak, Ryan G Porter, Eric Chaney, Ronit Barkalifa, Stephen A Boppart
Pneumatic otoscopy to assess the mobility of the tympanic membrane (TM) is a highly recommended diagnostic method of otitis media (OM), a widespread middle ear infection characterized by the fluid accumulation in the middle ear. Nonetheless, limited depth perception and subjective interpretation of small TM displacements have challenged the appropriate and efficient examination of TM dynamics experienced during OM. In this paper, a pneumatic otoscope integrated with low coherence interferometry (LCI) was adapted with a controlled pressure-generating system to record the pneumatic response of the TM and to estimate middle ear pressure (MEP)...
February 1, 2018: Biomedical Optics Express
Jennifer Chia Wee Fern, Shuji Ohsaki, Satoru Watano, Robert Pfeffer
The synthesis of nano-size drug particles by antisolvent crystallization using a porous hollow fiber membrane provides promising benefits such as the capability of continuous operation, low energy input, and ease of scale-up for a variety of industrial processes. Porous hollow fiber membranes have also been shown to produce more efficient mixing than conventional mixing equipment mostly because in mixing binary fluids, they provide sufficient mixing time, retention time, and a large contact interface for the drug solution and the antisolvent, allowing for the precise control of nucleation and crystal growth necessary to form nano-size particles...
March 15, 2018: International Journal of Pharmaceutics
Joo Myung Lee, Gilwoo Choi, Bon-Kwon Koo, Doyeon Hwang, Jonghanne Park, Jinlong Zhang, Kyung-Jin Kim, Yaliang Tong, Hyun Jin Kim, Leo Grady, Joon-Hyung Doh, Chang-Wook Nam, Eun-Seok Shin, Young-Seok Cho, Su-Yeon Choi, Eun Ju Chun, Jin-Ho Choi, Bjarne L Nørgaard, Evald Christiansen, Koen Niemen, Hiromasa Otake, Martin Penicka, Bernard de Bruyne, Takashi Kubo, Takashi Akasaka, Jagat Narula, Pamela S Douglas, Charles A Taylor, Hyo-Soo Kim
OBJECTIVES: We investigated the utility of noninvasive hemodynamic assessment in the identification of high-risk plaques that caused subsequent acute coronary syndrome (ACS). BACKGROUND: ACS is a critical event that impacts the prognosis of patients with coronary artery disease. However, the role of hemodynamic factors in the development of ACS is not well-known. METHODS: Seventy-two patients with clearly documented ACS and available coronary computed tomographic angiography (CTA) acquired between 1 month and 2 years before the development of ACS were included...
March 9, 2018: JACC. Cardiovascular Imaging
Rebecca C Gosling, Paul D Morris, Daniel A Silva Soto, Patricia V Lawford, D Rodney Hose, Julian P Gunn
OBJECTIVES: This study sought to assess the ability of a novel virtual coronary intervention (VCI) tool based on invasive angiography to predict the patient's physiological response to stenting. BACKGROUND: Fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) is associated with improved clinical and economic outcomes compared with angiographic guidance alone. Virtual (v)FFR can be calculated based upon a 3-dimensional (3D) reconstruction of the coronary anatomy from the angiogram, using computational fluid dynamics (CFD) modeling...
March 9, 2018: JACC. Cardiovascular Imaging
Waleed Brinjikji, Bongjae Chung, Ding Yong-Hong, John T Wald, Fernando Mut, Ramanathan Kadirvel, David F Kallmes, Aymeric Rouchaud, Giuseppe Lanzino, Juan R Cebral
BACKGROUND AND PURPOSE: Vertebrobasilar dolichoectatic and fusiform aneurysms (VBDAs) are known to have a poor natural history, with high rates of growth, rupture, and stroke. The purpose of this study was to identify hemodynamic characteristics that differ between VBDAs associated with growth, rupture, and stroke. MATERIALS AND METHODS: VBDAs with CT angiography or MR angiography followed longitudinally without treatment were studied. Unstable aneurysms were defined as those that grew or ruptured during follow-up...
March 16, 2018: Journal of Neurointerventional Surgery
Tsutomu Nomura, Munetaka Ushio, Kenji Kondo, Shigeru Kikuchi
OBJECTIVE: The purpose of this research is to examine the changes in nasal airflow dynamics before and after the nasal perforation repair. METHODS: Three dimensional (3D) models of the nasal cavity before and after septal perforation repair was reconstructed using preoperative and postoperative computed tomography (CT) images of a patient. The numerical simulation was carried out using ANSYS CFX V15.0. Pre- and post-operative models were compared by their velocity, pressure (P), pressure gradient (PG), wall shear (WS), shear strain rate (SSR) and turbulence kinetic energy (TKE) in three plains...
March 13, 2018: Auris, Nasus, Larynx
Amy Buchmann, Lisa J Fauci, Karin Leiderman, Eva Strawbridge, Longhua Zhao
Here, we study the fluid dynamics of a pair of rigid helices rotating at a constant velocity, tethered at their bases, in a viscous fluid. Our computations use a regularized Stokeslet framework, both with and without a bounding plane, so we are able to discern precisely what flow features are unaccounted for in studies that ignore the surface from which the helices emanate. We examine how the spacing and phase difference between identical rotating helices affects their pumping ability, axial thrust, and power requirements...
February 2018: Physical Review. E
Size Zheng, Katherine S Shing, Muhammad Sahimi
In this paper, the second in a series devoted to molecular modeling of protein aggregation, a mesoscale model of proteins together with extensive discontinuous molecular dynamics simulation is used to study the phenomenon in a confined medium. The medium, as a model of a crowded cellular environment, is represented by a spherical cavity, as well as cylindrical tubes with two aspect ratios. The aggregation process leads to the formation of β sheets and eventually fibrils, whose deposition on biological tissues is believed to be a major factor contributing to many neuro-degenerative diseases, such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis diseases...
March 14, 2018: Journal of Chemical Physics
Akiko Oota-Ishigaki, Toru Masuzawa, Kazuaki Nagayama
Thrombus formation on biomaterial surfaces with microstructures is complex and not fully understood. We have studied the micro-secondary flow around microstructures that causes components of blood to adhere physically in a low Reynolds number region. The purpose of this study was to investigate the effect of micro-column size on the adhesion phenomena and show a quantitative relationship between the micro-secondary flow and physical adhesion phenomena, considering microstructures of various sizes. The flow simulation and quantitative assessment of adhesion rates around micro-columns was conducted using four sizes of micro-columns...
March 1, 2018: International Journal of Artificial Organs
Qike Wang, Yidan Shang, Douglas S Hilton, Kiao Inthavong, Dong Zhang, Mark A Elgar
The elaborate bipectinate antennae of male moths are thought to increase their sensitivity to female sex pheromones, and so should be favoured by selection. Yet simple filamentous antennae are the most common structure among moths. The stereotypic arrangements of scales on the surface of antennae may resolve this paradox. We use computational fluid dynamics techniques to model how scales on the filamentous antennae of moths affect the passage of different particles in the airflow across the flagellum in both small and large moths...
March 14, 2018: Proceedings. Biological Sciences
Chang Heon Cheong, Seonhye Lee
The prevention of airborne infections in emergency departments is a very important issue. This study investigated the effects of architectural features on airborne pathogen dispersion in emergency departments by using a CFD (computational fluid dynamics) simulation tool. The study included three architectural features as the major variables: increased ventilation rate, inlet and outlet diffuser positions, and partitions between beds. The most effective method for preventing pathogen dispersion and reducing the pathogen concentration was found to be increasing the ventilation rate...
March 13, 2018: International Journal of Environmental Research and Public Health
Achmed Pircher, Margherita Montali, Peter Wostyn, Joachim Pircher, Jatta Berberat, Luca Remonda, Hanspeter E Killer
PURPOSE: To investigate the cerebrospinal fluid (CSF) dynamics along the entire optic nerve (ON) in patients with normal-tension glaucoma (NTG). METHODS: Retrospective analysis of computed tomographic (CT) cisternographies in Caucasian patients with NTG. Fifty-six patients (99 of 112 eyes) fulfilled the diagnostic criteria of NTG and underwent CT-cisternography. Twelve subjects without NTG (24 eyes) served as controls. Contrast-loaded cerebrospinal fluid (CLCSF) density measurements in Hounsfield units (HU) were performed at four defined regions along the ON and in the basal cistern...
March 12, 2018: Acta Ophthalmologica
Dong Zhang, Pengcheng Xu, Hongyu Qiao, Xin Liu, Liangping Luo, Wenhua Huang, Heye Zhang, Changzheng Shi
BACKGROUND: Cerebrovascular events are frequently associated with hemodynamic disturbance caused by internal carotid artery (ICA) stenosis. It is challenging to determine the ischemia-related carotid stenosis during the intervention only using digital subtracted angiography (DSA). Inspired by the performance of well-established FFRct technique in hemodynamic assessment of significant coronary stenosis, we introduced a pressure-based carotid arterial functional assessment (CAFA) index generated from computational fluid dynamic (CFD) simulation in DSA data, and investigated its feasibility in the assessment of hemodynamic disturbance preliminarily using pressure-wired measurement and arterial spin labeling (ASL) MRI as references...
March 12, 2018: Biomedical Engineering Online
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