NUMERICAL CHARACTERIZATION OF THE FLOW FIELD IN A FOUR-GENERATION AIRWAY

2008 ◽  
Vol 08 (01) ◽  
pp. 55-74 ◽  
Author(s):  
T. C. LAI ◽  
Y. S. MORSI ◽  
M. SINGH
Keyword(s):  
Reynolds Numbers ◽  
Bronchial Tree ◽  
Secondary Flows ◽  
Fourth Generation ◽  
Numerical Characterization ◽  
Wide Range ◽  
Symmetrical Model ◽  
Computational Fluid Dynamics Cfd ◽  
Insight Into

In this paper, various aspects of respiratory airflow generated from the branching network of tubes that make up the tracheal-bronchial tree are numerically analyzed using the computational fluid dynamics (CFD) package CFX. The model used is a four-generation airway that is geometrically similar to Weibel's symmetrical model. In the present analysis, two different models (in-plane and off-plane) are examined for a wide range of Reynolds numbers that correspond to human breathing conditions. The findings indicate that the secondary flow patterns generated become more significant as the flow passes from the trachea to the fourth-generation airway. Moreover, comparison between in-plane and off-plane models shows that the skewed velocity profiles and secondary flows for the in-plane model are more prominent than those for the off-plane one. In general, the model developed in this study is capable of providing an overall insight into the effect of fluid flow in multiple generations of the human upper respiratory airways.

scholarly journals Focusing of Particles in a Microchannel with Laser Engraved Groove Arrays

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 263
Author(s):  
Tianlong Zhang ◽  
Yigang Shen ◽  
Ryota Kiya ◽  
Dian Anggraini ◽  
Tao Tang ◽  
...  
Keyword(s):  
Open Space ◽  
Lateral Displacement ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Particle Sedimentation ◽  
Nanoparticle Separation ◽  
Wide Range ◽  
Fs Laser ◽  
Channel Bottom ◽  
Myoblast Cells

Continuous microfluidic focusing of particles, both synthetic and biological, is significant for a wide range of applications in industry, biology and biomedicine. In this study, we demonstrate the focusing of particles in a microchannel embedded with glass grooves engraved by femtosecond pulse (fs) laser. Results showed that the laser-engraved microstructures were capable of directing polystyrene particles and mouse myoblast cells (C2C12) towards the center of the microchannel at low Reynolds numbers (Re < 1). Numerical simulation revealed that localized side-to-center secondary flows induced by grooves at the channel bottom play an essential role in particle lateral displacement. Additionally, the focusing performance proved to be dependent on the angle of grooves and the middle open space between the grooves based on both experiments and simulation. Particle sedimentation rate was found to critically influence the focusing of particles of different sizes. Taking advantage of the size-dependent particle lateral displacement, selective focusing of micrometer particles was demonstrated. This study systematically investigated continuous particle focusing in a groove-embedded microchannel. We expect that this device will be used for further applications, such as cell sensing and nanoparticle separation in biological and biomedical areas.

Experimental characterization of three-dimensional corner flows at low Reynolds numbers

2012 ◽  
Vol 707 ◽  
pp. 37-52 ◽  
Author(s):  
J. Sznitman ◽  
L. Guglielmini ◽  
D. Clifton ◽  
D. Scobee ◽  
H. A. Stone ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Channel Cross Section ◽  
Experimental Characterization ◽  
Low Reynolds Numbers ◽  
Low Reynolds

AbstractWe investigate experimentally the characteristics of the flow field that develops at low Reynolds numbers ($\mathit{Re}\ll 1$) around a sharp $9{0}^{\ensuremath{\circ} } $ corner bounded by channel walls. Two-dimensional planar velocity fields are obtained using particle image velocimetry (PIV) conducted in a towing tank filled with a silicone oil of high viscosity. We find that, in the vicinity of the corner, the steady-state flow patterns bear the signature of a three-dimensional secondary flow, characterized by counter-rotating pairs of streamwise vortical structures and identified by the presence of non-vanishing transverse velocities (${u}_{z} $). These results are compared to numerical solutions of the incompressible flow as well as to predictions obtained, for a similar geometry, from an asymptotic expansion solution (Guglielmini et al., J. Fluid Mech., vol. 668, 2011, pp. 33–57). Furthermore, we discuss the influence of both Reynolds number and aspect ratio of the channel cross-section on the resulting secondary flows. This work represents, to the best of our knowledge, the first experimental characterization of the three-dimensional flow features arising in a pressure-driven flow near a corner at low Reynolds number.

Inertial focusing of spherical particles in rectangular microchannels over a wide range of Reynolds numbers

Lab on a Chip ◽  
2015 ◽  
Vol 15 (4) ◽  
pp. 1168-1177 ◽  
Author(s):  
Chao Liu ◽  
Guoqing Hu ◽  
Xingyu Jiang ◽  
Jiashu Sun
Keyword(s):  
Reynolds Numbers ◽  
Spherical Particles ◽  
Rectangular Microchannels ◽  
Inertial Focusing ◽  
Wide Range ◽  
Physical Insight ◽  
Insight Into

This work provides physical insight into the multiplex focusing of particles in rectangular microchannels with different geometries and Reynolds numbers.

scholarly journals Boule and the Evolutionary Origin of Metazoan Gametogenesis: A Grandpa's Tale

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
José M. Eirín-López ◽  
Juan Ausió
Keyword(s):  
Gene Family ◽  
Evolutionary Biology ◽  
Molecular Mechanisms ◽  
Evolutionary Origin ◽  
Reproductive Proteins ◽  
Wide Range ◽  
Animal Phyla ◽  
Rapid Divergence ◽  
Insight Into

The evolution of sex remains a hotly debated topic in evolutionary biology. In particular, studying the origins of the molecular mechanisms underlying sexual reproduction and gametogenesis (its fundamental component) in multicellular eukaryotes has been difficult due to the rapid divergence of many reproductive proteins, pleiotropy, and by the fact that only a very small number of reproductive proteins specifically involved in reproduction are conserved across lineages. Consequently, during the last decade, many efforts have been put into answering the following question: did gametogenesis evolve independently in different animal lineages or does it share a common evolutionary origin in a single ancestral prototype? Among the various approaches carried out in order to solve this question, the characterization of the evolution of the DAZ gene family holds much promise because these genes encode reproductive proteins that are conserved across a wide range of animal phyla. Within this family, BOULE is of special interest because it represents the most ancestral member of this gene family (the “grandfather” of DAZ). Furthermore, BOULE has attracted most of the attention since it represents an ancient male gametogenic factor with an essential reproductive-exclusive requirement in urbilaterians, constituting a core component of the reproductive prototype. Within this context, the aim of the present work is to provide an up-to-date insight into the studies that lead to the characterization of the DAZ family members and the implications in helping decipher the evolutionary origin of gametogenesis in metazoan animals.

scholarly journals Characterization of In Vivo Function(s) of Members of the Plant Mitochondrial Carrier Family

Biomolecules ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1226
Author(s):  
Adriano Nunes-Nesi ◽  
João Henrique F. Cavalcanti ◽  
Alisdair R. Fernie
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Genetic Variants ◽  
Mitochondrial Carrier ◽  
Wide Range ◽  
Mitochondrial Carrier Family ◽  
Insight Into ◽  
Green Lineage

Although structurally related, mitochondrial carrier family (MCF) proteins catalyze the specific transport of a range of diverse substrates including nucleotides, amino acids, dicarboxylates, tricarboxylates, cofactors, vitamins, phosphate and H+. Despite their name, they do not, however, always localize to the mitochondria, with plasma membrane, peroxisomal, chloroplast and thylakoid and endoplasmic reticulum localizations also being reported. The existence of plastid-specific MCF proteins is suggestive that the evolution of these proteins occurred after the separation of the green lineage. That said, plant-specific MCF proteins are not all plastid-localized, with members also situated at the endoplasmic reticulum and plasma membrane. While by no means yet comprehensive, the in vivo function of a wide range of these transporters is carried out here, and we discuss the employment of genetic variants of the MCF as a means to provide insight into their in vivo function complementary to that obtained from studies following their reconstitution into liposomes.

Experimental and Numerical Characterization of an Electrically Propelled Vehicles Battery Casing Including Battery Module

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Johan Anderson ◽  
Johan Sjöström ◽  
Petra Andersson ◽  
Francine Amon ◽  
Joakim Albrektsson
Keyword(s):  
Heat Transfer ◽  
Transfer Coefficients ◽  
Power Train ◽  
Fire Model ◽  
Heat Transfer Coefficients ◽  
Fire Resistance Test ◽  
Numerical Characterization ◽  
Computational Fluid Dynamics Cfd ◽  
Battery Module

This paper demonstrates the possibility to predict a battery system's performance in a fire resistance test according to the new amendment of United Nations Regulation No. 100 “Uniform Provisions Concerning the Approval of Vehicles with Regard to Specific Requirements for the Electric Power Train” (R100) based on careful measurements of the physical properties of the casing material, as well as modeling of the battery modules and computer simulations. The methodology of the work consists of estimating the heat transfer coefficients by using a gasoline pool fire model in the computational fluid dynamics (CFD) software FireDynamicsSimulator (FDS), followed by finite-element (FE) calculations of the temperatures in the battery

Static and Dynamic Analysis of a NACA 0021 Airfoil Section at Low Reynolds Numbers Based on Experiments and Computational Fluid Dynamics

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
David Holst ◽  
Francesco Balduzzi ◽  
Alessandro Bianchini ◽  
Benjamin Church ◽  
Felix Wegner ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Technical Literature ◽  
Open Field Behavior ◽  
Static And Dynamic Analysis ◽  
Wide Range ◽  
Experimental Apparatus ◽  
Low Reynolds ◽  
Insight Into

The wind industry needs airfoil data for ranges of angle of attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VAWTs) are even more affected by this need, since data sets across the full incidence range of 180 deg are necessary for a correct performance prediction at different tip-speed ratios. However, the relevant technical literature lacks data in deep and poststall regions for nearly every airfoil. Within this context, the present study shows experimental and numerical results for the well-known NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of a NACA 0021 airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two different Reynolds numbers (Re = 140 k and Re = 180 k): each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce both the static polars of the airfoil and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow field was then exploited both to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behavior. The present study is then thought to provide the scientific community with high quality, low-Reynolds airfoil data, which may enable in the near future a more effective design of Darrieus VAWTs.

Air-Side Performance Characterization of Air-to-Refrigerant Heat Exchangers Using Parallel Parameterized CFD

2013 ◽  
Author(s):  
Khaled Saleh ◽  
Weizhe Han ◽  
Vikrant Aute ◽  
Reinhard Radermacher
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Cfd Simulations ◽  
Cfd Models ◽  
F Factor ◽  
Wide Range ◽  
Different Types ◽  
Computational Fluid Dynamics Cfd ◽  
Friction Performance

The goal of the study presented in this paper is to use Computational Fluid Dynamics (CFD) to characterize the heat transfer and friction performance of fins used in air-to-refrigerant heat exchangers. Five different types of fins used in air-cooled heat exchangers (HXs) are studied using Parallel Parameterized CFD (PPCFD) approach described in this paper. The fin types considered in this paper are; Plain, Wavy, Slit, Super Slit, and Louver. 3-D CFD models are built and tested for these fin types. Based on the CFD results, air side heat transfer coefficient (HTC), Colburn j factor, Fanning f factor, and pressure drop are calculated. The results from CFD simulations are compared against experimental data from the literature for the different fin types and a good agreement is found between the two. In addition, the results from CFD simulations are used to evaluate the thermal and hydraulic performance for a wide range of heat exchanger parameters such as tube diameters, fin pitch, number of rows, and frontal air velocity. The results show the advantages of using PPCFD to efficiently develop correlations for different types of fins used in air-cooled HX, with significant reduction in engineering time. The PPCFD approach can be extended to efficiently optimize novel heat transfer surfaces.

Critical threshold in pipe flow transition

2008 ◽  
Vol 367 (1888) ◽  
pp. 545-560 ◽  
Author(s):  
Fernando Mellibovsky ◽  
Alvaro Meseguer
Keyword(s):  
Pipe Flow ◽  
Basin Of Attraction ◽  
Reynolds Numbers ◽  
Travelling Wave ◽  
Computational Method ◽  
Critical Threshold ◽  
Krylov Method ◽  
Numerical Characterization ◽  
Wide Range ◽  
Critical Amplitudes

This study provides a numerical characterization of the basin of attraction of the laminar Hagen–Poiseuille flow by measuring the minimal amplitude of a perturbation required to trigger transition. For pressure-driven pipe flow, the analysis presented here covers autonomous and impulsive scenarios where either the flow is perturbed with an initial disturbance with a well-defined norm or perturbed by means of local impulsive forcing that mimics injections through the pipe wall. In both the cases, the exploration is carried out for a wide range of Reynolds numbers by means of a computational method that numerically resolves the transitional dynamics. For , the present work provides critical amplitudes that decay as Re −3/2 and Re −1 for the autonomous and impulsive scenarios, respectively. For Re =2875, accurate threshold amplitudes are found for constant mass-flux pipe by means of a shooting method that provides critical trajectories that never relaminarize or trigger transition. These transient states are used as initial guesses in a damped Newton–Krylov method formulated to find periodic travelling wave solutions that either travel downstream or exhibit a helicoidal advection.

Numerical Characterization of the Inlet Flow for Eleven Radial Turbomachines

2010 ◽  
Author(s):  
Nathan O. Packard ◽  
David Japikse ◽  
R. Daniel Maynes ◽  
Steven E. Gorrell
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Model Development ◽  
Leading Edge ◽  
Inlet Flow ◽  
Numerical Characterization ◽  
Study Results ◽  
High Gradients ◽  
Computational Fluid Dynamics Cfd

Successful modeling of a turbomachine stage requires attention to many details, including a realistic understanding of the inlet flow field. Various levels of modeling, from 1-D to 3-D viscous, plus various levels of measurement, from a simple inlet shroud pressure tap to complex inlet surveys, are considered in design and development work. In this study, a careful review is made of measurement and calculation options for inlet modeling. Historical practice places a static pressure tap on the shroud just upstream of the impeller leading edge for experimental characterization of centrifugal turbomachines. Previously developed statistics based meanline models rely in part on this measured data. However, the location of the tap may be vulnerable to high gradients which would decrease the dependability of the developed models. Computational Fluid Dynamics (CFD) and Multi-Stream Tube (MST) analyses were performed to test the appropriateness of the historically placed static pressure tap location and to characterize the inlet flow of typical radial flow turbomachines. Eleven ConceptsNREC machines were chosen for investigation to provide a wide variety of inlet geometric and flow conditions. The results derived from the CFD and MST analyses suggest that the historically placed static pressure tap location is an inappropriate anchor point for model development. While the focus of this work is not intended to reveal why the inlet behaves as it does, it does reveal that for a wide variety of inlet configurations and impeller sizes, the presumed inlet tap location should no longer be used in experimental work. Steep gradients in the static pressure indicate that a relatively minor movement of the static pressure tap would significantly alter the experimental measurements and generate noise in statistical modeling. While large variations in the pressure field are apparent near the impeller leading edge for all machines considered, the study results show that the flow field is uniform and very predictable when well upstream of the impeller leading edge. A point approximately 3 blade heights upstream from the impeller leading edge appears to be a sound location to anchor 1-D meanline model development, as well as for future experimental investigation.

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