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Computational fluid dynamics

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https://www.readbyqxmd.com/read/28747812/numerical-analysis-of-the-influence-of-low-frequency-vibration-on-bubble-growth
#1
D Han, Mark A Kedzierski
Numerical simulation of bubble growth during pool boiling under the influence of low frequency vibration was performed to understand the influence of common vibrations such as those induced by wind, highway transportation, and nearby mechanical devices on the performance of thermal systems that rely on boiling. The simulations were done for saturated R123 boiling at 277.6 K with a 15 K wall superheat. The numerical volume-of-fluid method (fixed grid) was used to define the liquid-vapor interface. The basic bubble growth characteristics including the bubble departure diameter and the bubble departure time were determined as a function of the bubble contact angle (20°-80°), the vibration displacement (10 µm-50 µm), the vibration frequency (5 Hz-25 Hz), and the initial vibration direction (positive or negative)...
2017: International Journal of Transport Phenomena
https://www.readbyqxmd.com/read/28745409/assessment-of-reynolds-stress-components-and-turbulent-pressure-loss-using-4d-flow-mri-with-extended-motion-encoding
#2
Henrik Haraldsson, Sarah Kefayati, Sinyeob Ahn, Petter Dyverfeldt, Jonas Lantz, Matts Karlsson, Gerhard Laub, Tino Ebbers, David Saloner
PURPOSE: To measure the Reynolds stress tensor using 4D flow MRI, and to evaluate its contribution to computed pressure maps. METHODS: A method to assess both velocity and Reynolds stress using 4D flow MRI is presented and evaluated. The Reynolds stress is compared by cross-sectional integrals of the Reynolds stress invariants. Pressure maps are computed using the pressure Poisson equation-both including and neglecting the Reynolds stress. RESULT: Good agreement is seen for Reynolds stress between computational fluid dynamics, simulated MRI, and MRI experiment...
July 26, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28744968/benchmark-problems-for-numerical-treatment-of-backflow-at-open-boundaries
#3
C Bertoglio, A Caiazzo, Y Bazilevs, M Braack, M Esmaily, V Gravemeier, A Marsden, O Pironneau, I E Vignon-Clementel, W A Wall
In computational fluid dynamics, incoming velocity at open boundaries, or backflow, often yields to unphysical instabilities already for moderate Reynolds numbers. Several treatments to overcome these backflow instabilities have been proposed in the literature. However, these approaches have not yet been compared in detail in terms of accuracy in different physiological regimes, in particular due to the difficulty to generate stable reference solutions apart from analytical forms. In this work, we present a set of benchmark problems in order to compare different methods in different backflow regimes (with a full reversal flow and with propagating vortices after a stenosis)...
July 25, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28744907/design-and-hemocompatibility-analysis-of-a-double-suction-injection-suspension-blood-pump-using-computational-fluid-dynamics-methods
#4
Yue Wu, Liangfan Zhu, Yun Luo
The blood pump has become a possible solution to heart diseases. For the prevention of device failure and hemocompatibility problems, a rotary pump with suspended bearing is a preferred solution. In our previous work, a novel injection suspension method has been introduced to levitate the rotor. The suspension method is totally passive. This study aims to apply this suspension method to a double-suction pump, and the property of the pump was investigated using computational fluid dynamics (CFD) methods. The flow field of the pump is simulated based on the SST k-ω turbulent model...
July 26, 2017: Artificial Organs
https://www.readbyqxmd.com/read/28744840/organ-dynamics-and-fluid-dynamics-of-the-hh25-chick-embryonic-cardiac-ventricle-as-revealed-by-a-novel-4d-high-frequency-ultrasound-imaging-technique-and-computational-flow-simulations
#5
Sheldon Ho, Germaine Xin Yi Tan, Toon Jin Foo, Nhan Phan-Thien, Choon Hwai Yap
Past literature has provided evidence that a normal mechanical force environment of blood flow may guide normal development while an abnormal environment can lead to congenital malformations, thus warranting further studies on embryonic cardiovascular flow dynamics. In the current study, we developed a non-invasive 4D high-frequency ultrasound technique, and use it to analyze cardiovascular organ dynamics and flow dynamics. Three chick embryos at stage HH25 were scanned with high frequency ultrasound in cine-B-mode at multiple planes spaced at 0...
July 25, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28744828/review-of-numerical-methods-for-simulation-of-mechanical-heart-valves-and-the-potential-for-blood-clotting
#6
Mohamad Shukri Zakaria, Farzad Ismail, Masaaki Tamagawa, Ahmad Fazli Abdul Aziz, Surjatin Wiriadidjaja, Adi Azrif Basri, Kamarul Arifin Ahmad
Even though the mechanical heart valve (MHV) has been used routinely in clinical practice for over 60 years, the occurrence of serious complications such as blood clotting remains to be elucidated. This paper reviews the progress that has been made over the years in terms of numerical simulation method and the contribution of abnormal flow toward blood clotting from MHVs in the aortic position. It is believed that this review would likely be of interest to some readers in various disciplines, such as engineers, scientists, mathematicians and surgeons, to understand the phenomenon of blood clotting in MHVs through computational fluid dynamics...
July 26, 2017: Medical & Biological Engineering & Computing
https://www.readbyqxmd.com/read/28743094/a-personalized-medicine-approach-to-the-design-of-dry-powder-inhalers-selecting-the-optimal-amount-of-bypass
#7
Thomas Kopsch, Darragh Murnane, Digby Symons
In dry powder inhalers (DPIs) the patient's inhalation manoeuvre strongly influences the release of drug. Drug release from a DPI may also be influenced by the size of any air bypass incorporated in the device. If the amount of bypass is high less air flows through the entrainment geometry and the release rate is lower. In this study we propose to reduce the intra- and inter-patient variations of drug release by controlling the amount of air bypass in a DPI. A fast computational method is proposed that can predict how much bypass is needed for a specified drug delivery rate for a particular patient...
July 22, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28742827/the-relationship-between-coronary-artery-distensibility-and-fractional-flow-reserve
#8
Andy S C Yong, Ashkan Javadzadegan, William F Fearon, Abouzar Moshfegh, Jerrett K Lau, Stephen Nicholls, Martin K C Ng, Leonard Kritharides
Discordance between angiography-based anatomical assessment of coronary stenosis severity and fractional flow reserve (FFR) has been attributed to several factors including lesion length and irregularity, and the myocardial territory supplied by the target vessel. We sought to examine if coronary arterial distensibility is an independent contributor to this discordance. There were two parts to this study. The first consisted of "in silico" models of 26 human coronary arteries. Computational fluid dynamics-derived FFR was calculated for fully rigid, partially distensible and fully distensible models of the 26 arteries...
2017: PloS One
https://www.readbyqxmd.com/read/28742031/patient-specific-left-ventricular-flow-simulations-from-transthoracic-echocardiography-robustness-evaluation-and-validation-against-ultrasound-doppler-and-magnetic-resonance-imaging
#9
David Larsson, Jeannette H Spuhler, Sven Petersson, Tim Nordenfur, Massimiliano Colarieti-Tosti, Johan Hoffman, Reidar Winter, Matilda Larsson
The combination of medical imaging with computational fluid dynamics (CFD) has enabled the study of 3D blood flow on a patient-specific level. However, with models based on gated high-resolution data, the study of transient flows, and any model implementation into routine cardiac care, is challenging. The present paper presents a novel pathway for patient-specific CFD modelling of the left ventricle (LV), using 4D transthoracic echocardiography (TTE) as input modality. To evaluate the clinical usability, two sub-studies were performed...
July 21, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28741084/towards-the-prediction-of-flow-induced-shear-stress-distributions-experienced-by-breast-cancer-cells-in-the-lymphatics
#10
S T Morley, D T Newport, M T Walsh
Tumour metastasis in the lymphatics is a crucial step in the progression of breast cancer. The dynamics by which breast cancer cells (BCCs) travel in the lymphatics remains poorly understood. The goal of this work is to develop a model capable of predicting the shear stresses metastasising BCCs experience using numerical and experimental techniques. This paper models the fluidic transport of large particles ([Formula: see text] where [Formula: see text] is the particle diameter and W is the channel width) subjected to lymphatic flow conditions ([Formula: see text]), in a [Formula: see text] microchannel...
July 24, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28735415/cfd-simulation-of-aerosol-delivery-to-a-human-lung-via-surface-acoustic-wave-nebulization
#11
Morteza Yousefi, Oveis Pourmehran, Mofid Gorji-Bandpy, Kiao Inthavong, Leslie Yeo, Jiyuan Tu
Administration of drug in the form of particles through inhalation is generally preferable in the treatment of respiratory disorders. Conventional inhalation therapy devices such as inhalers and nebulizers, nevertheless, suffer from low delivery efficiencies, wherein only a small fraction of the inhaled drug reaches the lower respiratory tract. This is primarily because these devices are not able to produce a sufficiently fine drug mist that has aerodynamic diameters on the order of a few microns. This study employs computational fluid dynamics to investigate the transport and deposition of the drug particles produced by a new aerosolization technique driven by surface acoustic waves (SAWs) into an in silico lung model geometrically reconstructed using computed tomography scanning...
July 22, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28733923/cardiovascular-mechanics-in-the-early-stages-of-pulmonary-hypertension-a-computational-study
#12
Sebastián Acosta, Charles Puelz, Béatrice Rivière, Daniel J Penny, Ken M Brady, Craig G Rusin
We formulate and study a new mathematical model of pulmonary hypertension. Based on principles of fluid and elastic dynamics, we introduce a model that quantifies the stiffening of pulmonary vasculature (arteries and arterioles) to reproduce the hemodynamics of the pulmonary system, including physiologically consistent dependence between compliance and resistance. This pulmonary model is embedded in a closed-loop network of the major vessels in the body, approximated as one-dimensional elastic tubes, and zero-dimensional models for the heart and other organs...
July 21, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28728972/numerical-characterisation-of-one-step-and-three-step-solar-air-heating-collectors-used-for-cocoa-bean-solar-drying
#13
Elder Mendoza Orbegoso, Rafael Saavedra, Daniel Marcelo, Raúl La Madrid
In the northern coastal and jungle areas of Peru, cocoa beans are dried using artisan methods, such as direct exposure to sunlight. This traditional process is time intensive, leading to a reduction in productivity and, therefore, delays in delivery times. The present study was intended to numerically characterise the thermal behaviour of three configurations of solar air heating collectors in order to determine which demonstrated the best thermal performance under several controlled operating conditions. For this purpose, a computational fluid dynamics model was developed to describe the simultaneous convective and radiative heat transfer phenomena under several operation conditions...
July 17, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28721492/peristaltic-like-motion-of-the-human-fetal-right-ventricle-and-its-effects-on-fluid-dynamics-and-energy-dynamics
#14
Hadi Wiputra, Guat Ling Lim, Khong Chun Chua, R Nivetha, Sanah Merchant Soomar, Arijit Biwas, Citra Nurfarah Zaini Mattar, Hwa Liang Leo, Choon Hwai Yap
In both adult human and canine, the cardiac right ventricle (RV) is known to exhibit a peristaltic-like motion, where RV sinus (inflow region) contracts first and the infundibulum (outflow region) later, in a wave-like contraction motion. The delay in contraction between the sinus and infundibulum averaged at 15% of the cardiac cycle and was estimated to produce an intra-ventricular pressure difference of 15 mmHg. However, whether such a contractile motion occurs in human fetuses as well, its effects on hemodynamics remains unknown, and are the subject of the current study...
July 18, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28718208/quantification-of-nasal-airflow-resistance-in-english-bulldogs-using-computed-tomography-and-computational-fluid-dynamics
#15
Eric T Hostnik, Brian A Scansen, Rachel Zielinski, Samir N Ghadiali
Stenotic nares, edematous intranasal turbinates, mucosal swelling, and an elongated, thickened soft palate are common sources of airflow resistance for dogs with brachycephalic airway syndrome. Surgery has focused on enlarging the nasal apertures and reducing tissue of the soft palate. However, objective measures of surgical efficacy are lacking. Twenty-one English bulldogs without previous surgery were recruited for this prospective, pilot study. Computed tomography was performed using conscious sedation and without endotracheal intubation using a 128 multidetector computed tomography scanner...
July 17, 2017: Veterinary Radiology & Ultrasound
https://www.readbyqxmd.com/read/28718049/good-things-in-small-packages-an-innovative-delivery-approach-for-inhaled-insulin
#16
James B Fink, Lisa Molloy, John S Patton, Valdecir Castor Galindo-Filho, Jacqueline de Melo Barcelar, Luciana Alcoforado, Simone Cristina Soares Brandão, Armèle Dornelas de Andrade
PURPOSE: The design development of a small, hand held, battery operated, breath actuated inhaler as a drug/device platform for inhaled insulin posed a number of technical challenges. Our goal was to optimize lung deposition and distribution with aerosol generators producing 3-6 μm particle size distribution. METHODS: In silico modeling with computational fluid dynamics (CFD) and in vitro testing of device components were assessed using an Alberta idealized adult airway (Copley, UK) to optimize mouthpiece and aerosol path design for dose delivered distal to the trachea...
July 17, 2017: Pharmaceutical Research
https://www.readbyqxmd.com/read/28717801/mimicking-arterial-thrombosis-in-a-3d-printed-microfluidic-in-vitro-vascular-model-based-on-computed-tomography-angiography-data
#17
Pedro F Costa, Hugo J Albers, John E A Linssen, Heleen H T Middelkamp, Linda van der Hout, Robert Passier, Albert van den Berg, Jos Malda, Andries D van der Meer
Arterial thrombosis is the main instigating factor of heart attacks and strokes, which result in over 14 million deaths worldwide every year. The mechanism of thrombosis involves factors from the blood and the vessel wall, and it also relies strongly on 3D vessel geometry and local blood flow patterns. Microfluidic chip-based vascular models allow controlled in vitro studies of the interaction between vessel wall and blood in thrombosis, but until now, they could not fully recapitulate the 3D geometry and blood flow patterns of real-life healthy or diseased arteries...
July 18, 2017: Lab on a Chip
https://www.readbyqxmd.com/read/28716447/elevated-wall-shear-stress-in-aortic-type-b-dissection-may-relate-to-retrograde-aortic-type-a-dissection-a-computational-fluid-dynamics-pilot-study
#18
A Osswald, C Karmonik, J R Anderson, F Rengier, M Karck, J Engelke, K Kallenbach, D Kotelis, S Partovi, D Böckler, A Ruhparwar
OBJECTIVE: Retrograde aortic type A dissection (RTAD) is a known complication in patients with aortic type B dissection. The purpose of this computational fluid dynamics (CFD) study was to identify haemodynamic risk factors for the occurrence of RTAD. METHODS: Computed tomographic angiography (CTA) images of 10 patients with type B dissections, who subsequently developed a RTAD, were retrospectively analysed together with patients constituting a control group (n = 10) where no further vascular events after the initial type B dissection occurred...
July 14, 2017: European Journal of Vascular and Endovascular Surgery
https://www.readbyqxmd.com/read/28716304/three-dimensional-computational-model-of-a-blood-oxygenator-reconstructed-from-micro-ct-scans
#19
C D'Onofrio, R van Loon, S Rolland, R Johnston, L North, S Brown, R Phillips, J Sienz
Cardiopulmonary bypass procedures are one of the most common operations and blood oxygenators are the centre piece for the heart-lung machines. Blood oxygenators have been tested as entire devices but intricate details on the flow field inside the oxygenators remain unknown. In this study, a novel method is presented to analyse the flow field inside oxygenators based on micro Computed Tomography (μCT) scans. Two Hollow Fibre Membrane (HFM) oxygenator prototypes were scanned and three-dimensional full scale models that capture the device-specific fibre distributions are set up for computational fluid dynamics analysis...
July 14, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28715329/phased-array-imaging-of-complex-geometry-composite-components
#20
Alex J Brath, Francesco Simonetti, Francesco Simonetti
Progress in computational fluid dynamics (CFD) and the availability of new composite materials are driving major advances in the design of aerospace engine components which now have highly complex geometries optimized to maximize system performance. However, shape complexity poses significant challenges to traditional non-destructive evaluation (NDE) methods whose sensitivity and selectivity rapidly decrease as surface curvature increases. Additionally, new aerospace materials typically exhibit an intricate microstructure that further complicates the inspection...
July 13, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
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