scholarly journals Characterizing the Shearing Stresses within the CDC Biofilm Reactor Using Computational Fluid Dynamics

2021 ◽  
Vol 9 (8) ◽  
pp. 1709
Author(s):  
Erick Johnson ◽  
Theodore Petersen ◽  
Darla M. Goeres
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Critical Factor ◽  
Test Methods ◽  
Standard Test ◽  
Biofilm Reactor ◽  
Shear Stresses ◽  
Three Dimensional Model

Shearing stresses are known to be a critical factor impacting the growth and physiology of biofilms, but the underlying fluid dynamics within biofilm reactors are rarely well characterized and not always considered when a researcher decides which biofilm reactor to use. The CDC biofilm reactor is referenced in validated Standard Test Methods and US EPA guidance documents. The driving fluid dynamics within the CDC biofilm reactor were investigated using computational fluid dynamics. An unsteady, three-dimensional model of the CDC reactor was simulated at a rotation rate of 125 RPM. The reactor showed turbulent structures, with shear stresses averaging near 0.365 ± 0.074 Pa across all 24 coupons. The pressure variation on the coupon surfaces was found to be larger, with a continuous 2–3 Pa amplitude, coinciding with the baffle passage. Computational fluid dynamics was shown to be a powerful tool for defining key fluid dynamic parameters at a high fidelity within the CDC biofilm reactor. The consistency of the shear stresses and pressures and the unsteadiness of the flow within the CDC reactor may help explain its reproducibility in laboratory studies. The computational model will enable researchers to make an informed decision whether the fluid dynamics present in the CDC biofilm reactor are appropriate for their research.

scholarly journals The Effect of Depth on Drag During the Streamlined Glide: A Three-Dimensional CFD Analysis

2012 ◽  
Vol 33 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Maria Novais ◽  
António Silva ◽  
Vishveshwar Mantha ◽  
Rui Ramos ◽  
Abel Rouboa ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Hydrodynamic Drag ◽  
Cfd Analysis ◽  
Three Dimensional Model ◽  
Commercial Code ◽  
Elite Level ◽  
Computation Fluid Dynamic

The Effect of Depth on Drag During the Streamlined Glide: A Three-Dimensional CFD AnalysisThe aim of this study was to analyze the effects of depth on drag during the streamlined glide in swimming using Computational Fluid Dynamics. The Computation Fluid Dynamic analysis consisted of using a three-dimensional mesh of cells that simulates the flow around the considered domain. We used the K-epsilon turbulent model implemented in the commercial code Fluent® and applied it to the flow around a three-dimensional model of an Olympic swimmer. The swimmer was modeled as if he were gliding underwater in a streamlined prone position, with hands overlapping, head between the extended arms, feet together and plantar flexed. Steady-state computational fluid dynamics analyses were performed using the Fluent® code and the drag coefficient and the drag force was calculated for velocities ranging from 1.5 to 2.5 m/s, in increments of 0.50m/s, which represents the velocity range used by club to elite level swimmers during the push-off and glide following a turn. The swimmer model middle line was placed at different water depths between 0 and 1.0 m underwater, in 0.25m increments. Hydrodynamic drag decreased with depth, although after 0.75m values remained almost constant. Water depth seems to have a positive effect on reducing hydrodynamic drag during the gliding. Although increasing depth position could contribute to decrease hydrodynamic drag, this reduction seems to be lower with depth, especially after 0.75 m depth, thus suggesting that possibly performing the underwater gliding more than 0.75 m depth could not be to the benefit of the swimmer.

scholarly journals Three-dimensional multiphase flow computational fluid dynamics models for proton exchange membrane fuel cell: A theoretical development

2017 ◽  
Vol 9 (1) ◽  
pp. 3-25 ◽  
Author(s):  
Jean-Paul Kone ◽  
Xinyu Zhang ◽  
Yuying Yan ◽  
Guilin Hu ◽  
Goodarz Ahmadi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fuel Cell ◽  
Multiphase Flow ◽  
Proton Exchange Membrane ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Proton Exchange ◽  
Dynamics Models ◽  
Exchange Membrane

A review of published three-dimensional, computational fluid dynamics models for proton exchange membrane fuel cells that accounts for multiphase flow is presented. The models can be categorized as models for transport phenomena, geometry or operating condition effects, and thermal effects. The influences of heat and water management on the fuel cell performance have been repeatedly addressed, and these still remain two central issues in proton exchange membrane fuel cell technology. The strengths and weaknesses of the models, the modelling assumptions, and the model validation are discussed. The salient numerical features of the models are examined, and an overview of the most commonly used computational fluid dynamic codes for the numerical modelling of proton exchange membrane fuel cells is given. Comprehensive three-dimensional multiphase flow computational fluid dynamic models accounting for the major transport phenomena inside a complete cell have been developed. However, it has been noted that more research is required to develop models that include among other things, the detailed composition and structure of the catalyst layers, the effects of water droplets movement in the gas flow channels, the consideration of phase change in both the anode and the cathode sides of the fuel cell, and dissolved water transport.

Anatomically based three-dimensional model of airways to simulate flow and particle transport using computational fluid dynamics

2005 ◽  
Vol 98 (3) ◽  
pp. 970-980 ◽  
Author(s):  
Caroline van Ertbruggen ◽  
Charles Hirsch ◽  
Manuel Paiva
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Deposition ◽  
Gas Flow ◽  
Three Dimensional ◽  
Bronchial Tree ◽  
Inspiratory Flow ◽  
Three Dimensional Model ◽  
Viscous Pressure ◽  
Curved Ducts

We have studied gas flow and particle deposition in a realistic three-dimensional (3D) model of the bronchial tree, extending from the trachea to the segmental bronchi (7th airway generation for the most distal ones) using computational fluid dynamics. The model is based on the morphometrical data of Horsfield et al. (Horsfield K, Dart G, Olson DE, Filley GF, and Cumming G. J Appl Physiol 31: 207–217, 1971) and on bronchoscopic and computerized tomography images, which give the spatial 3D orientation of the curved ducts. It incorporates realistic angles of successive branching planes. Steady inspiratory flow varying between 50 and 500 cm3/s was simulated, as well as deposition of spherical aerosol particles (1–7 μm diameter, 1 g/cm3 density). Flow simulations indicated nonfully developed flows in the branches due to their relative short lengths. Velocity flow profiles in the segmental bronchi, taken one diameter downstream of the bifurcation, were distorted compared with the flow in a simple curved tube, and wide patterns of secondary flow fields were observed. Both were due to the asymmetrical 3D configuration of the bifurcating network. Viscous pressure drop in the model was compared with results obtained by Pedley et al. (Pedley TJ, Schroter RC, and Sudlow MF. Respir Physiol 9: 387–405, 1970), which are shown to be a good first approximation. Particle deposition increased with particle size and was minimal for ∼200 cm3/s inspiratory flow, but it was highly heterogeneous for branches of the same generation.

scholarly journals Numerical Simulation of a Propeller-Type Turbine for In-Pipe Installation

2021 ◽  
Vol 83 (1) ◽  
pp. 1-16
Author(s):  
Oscar Darío Monsalve Cifuentes ◽  
Jonathan Graciano Uribe ◽  
Diego Andrés Hincapié Zuluaga
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Pipe Wall ◽  
Three Dimensional ◽  
Hydraulic Efficiency ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Mesh Independence ◽  
Using Data

In this work, a 76 mm diameter propeller-type turbine is numerically investigated using a parametric study and computational fluid dynamics. The three-dimensional model of the turbine is modeled using data available in the bibliography. A mesh independence study is carried out utilizing a tetrahedron-based mesh with inflation layers around the turbine blade and the pipe wall. The best efficiency point is determined by the maximum hydraulic efficiency of 64.46 %, at a flow rate of 9.72x10-3 m3/s , a head drop of 1.76 m, and a mechanical power of 107.83 W. Additionally, the dimensionless distance y+, pressure, and velocity contours are shown.

Analysis of Velopharyngeal Functions Using Computational Fluid Dynamics Simulations

2019 ◽  
Vol 128 (8) ◽  
pp. 742-748 ◽  
Author(s):  
Hanyao Huang ◽  
Xu Cheng ◽  
Yang Wang ◽  
Dantong Huang ◽  
Yuhao Wei ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Dynamic Features ◽  
Upper Airways ◽  
Dynamic Simulations ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Objectives: Competent velopharyngeal (VP) function is the basis for normal speech. Understanding how VP structure influences the airflow during speech details is essential to the surgical improvement of pharyngoplasty. In this study, we aimed to illuminate the airflow features corresponding to various VP closure states using computed dynamic simulations. Methods: Three-dimensional models of the upper airways were established based on computed tomography of 8 volunteers. The velopharyngeal port was simulated by a cylinder. Computational fluid dynamics simulations were applied to illustrate the correlation between the VP port size and the airflow parameters, including the flow velocity, pressure in the velopharyngeal port, as well as the pressure in oral and nasal cavity. Results: The airflow dynamics at the velopharynx were maintained in the same velopharyngeal pattern as the area of the velopharyngeal port increased from 0 to 25 mm2. A total of 5 airflow patterns with distinct features were captured, corresponding to adequate closure, adequate/borderline closure (Class I and II), borderline/inadequate closure, and inadequate closure. The maximal orifice area that could be tolerated for adequate VP closure was determined to be 2.01 mm2. Conclusion: Different VP functions are of characteristic airflow dynamic features. Computational fluid dynamic simulation is of application potential in individualized VP surgery planning.

scholarly journals Perfusion Characteristics of the Human Hepatic Microcirculation Based on Three-Dimensional Reconstructions and Computational Fluid Dynamic Analysis

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Charlotte Debbaut ◽  
Jan Vierendeels ◽  
Christophe Casteleyn ◽  
Pieter Cornillie ◽  
Denis Van Loo ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Porous Medium ◽  
Human Liver ◽  
Three Dimensional ◽  
Central Vein ◽  
Shear Stresses ◽  
Corrosion Casting ◽  
Hepatic Microcirculation ◽  
Liver Microcirculation

The perfusion of the liver microcirculation is often analyzed in terms of idealized functional units (hexagonal liver lobules) based on a porous medium approach. More elaborate research is essential to assess the validity of this approach and to provide a more adequate and quantitative characterization of the liver microcirculation. To this end, we modeled the perfusion of the liver microcirculation using an image-based three-dimensional (3D) reconstruction of human liver sinusoids and computational fluid dynamics techniques. After vascular corrosion casting, a microvascular sample (±0.134 mm3) representing three liver lobules, was dissected from a human liver vascular replica and scanned using a high resolution (2.6 μm) micro-CT scanner. Following image processing, a cube (0.15 × 0.15 × 0.15 mm3) representing a sample of intertwined and interconnected sinusoids, was isolated from the 3D reconstructed dataset to define the fluid domain. Three models were studied to simulate flow along three orthogonal directions (i.e., parallel to the central vein and in the radial and circumferential directions of the lobule). Inflow and outflow guidances were added to facilitate solution convergence, and good quality volume meshes were obtained using approximately 9 × 106 tetrahedral cells. Subsequently, three computational fluid dynamics models were generated and solved assuming Newtonian liquid properties (viscosity 3.5 mPa s). Post-processing allowed to visualize and quantify the microvascular flow characteristics, to calculate the permeability tensor and corresponding principal permeability axes, as well as the 3D porosity. The computational fluid dynamics simulations provided data on pressure differences, preferential flow pathways and wall shear stresses. Notably, the pressure difference resulting from the flow simulation parallel to the central vein (0–100 Pa) was clearly smaller than the difference from the radial (0–170 Pa) and circumferential (0–180 Pa) flow directions. This resulted in a higher permeability along the central vein direction (kd,33 = 3.64 × 10−14 m2) in comparison with the radial (kd,11 = 1.56 × 10−14 m2) and circumferential (kd,22 = 1.75 × 10−14 m2) permeabilities which were approximately equal. The mean 3D porosity was 14.3. Our data indicate that the human hepatic microcirculation is characterized by a higher permeability along the central vein direction, and an about two times lower permeability along the radial and circumferential directions of a lobule. Since the permeability coefficients depend on the flow direction, (porous medium) liver microcirculation models should take into account sinusoidal anisotropy.

scholarly journals Design of a three-dimensional hand/forearm model to apply computational fluid dynamics

2010 ◽  
Vol 53 (2) ◽  
pp. 436-442 ◽  
Author(s):  
Daniel Almeida Marinho ◽  
Victor Machado Reis ◽  
João Paulo Vilas-Boas ◽  
Francisco Bessone Alves ◽  
Leandro Machado ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Digital Model ◽  
Human Hand ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Perfect Agreement ◽  
Computational Data ◽  
Processing Techniques

The purpose of this study was to develop a three-dimensional digital model of a human hand and forearm to apply Computational Fluid Dynamics to propulsion analysis in swimming. Computer tomography scans of the hand and forearm of an Olympic swimmer were applied. The data were converted, using image processing techniques, into relevant coordinate input, which could be used in Computational Fluid Dynamics software. From that analysis, it was possible to verify an almost perfect agreement between the true human segment and the digital model. This technique could be used as a means to overcome the difficulties in developing a true three-dimensional model of a specific segment of the human body. Additionally, it could be used to improve the use of Computational Fluid Dynamics generally in sports and specifically in swimming studies, decreasing the gap between the experimental and the computational data.

A Computational Fluid Dynamics Comparison of Wells Turbine Blades in 2D and 3D Cascade Flow

2002 ◽  
Author(s):  
John Daly ◽  
Patrick Frawley ◽  
Ajit Thakker
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Primary Objective ◽  
Two Dimensional ◽  
Three Dimensional Model ◽  
Wells Turbine ◽  
Cascade Flow ◽  
Cascade Models

This paper deals with the application of Computational Fluid Dynamics (CFD) to the analysis of the aerodynamic characteristics of symmetrical airfoil blades in 2-Dimensional cascade flow. Theoretical two dimensional cascade analyses of Wells Turbines blade profiles have been used in the past to predict the performance of three-dimensional turbines. The use of two-dimensional cascade models is beneficial as it allows the analysis and optimisation of the blade profile with approximately one tenth the computational requirements of a three-dimensional model. The primary objective of this work was to provide further validation of the use of two dimensional cascade models by comparing the computational predictions with traditional theoretical calculation results and also with three-dimensional turbine results. A secondary objective was to use the two dimensional cascade models to better understand the blade interaction effects that occur in the Wells Turbine. The model was used to analyse and compare three different blade profiles at different cascade settings. This paper presents the results of the numerical investigation, the validation of the results and the subsequent analysis.

A computational fluid dynamics model of a solid oxide fuel cell

2005 ◽  
Vol 219 (3) ◽  
pp. 159-167 ◽  
Author(s):  
K Sudaprasert ◽  
R P Travis ◽  
R F Martinez-Botas
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Thermal Stresses ◽  
Flow Direction ◽  
Three Dimensional ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Three Dimensional Model

In this work a three-dimensional model of a solid oxide fuel cell (SOFC) has been developed and is used to predict the temperature, concentration distribution and velocity profile across the cell. This model employs Users’ Subroutines in a commercial computational fluid dynamics (CFD) code to simulate the electrochemical reactions. The results show both fuel concentration and current density decreasing along the flow direction. The temperature differences are significant with the hottest point located in middle of the active area. Increasing the operating temperature is shown to reduce the effect of polarization that hampers the cell performance, although other issues such as thermal stresses and reduced material choices are more significant.

Computational Fluid Dynamics Applied to Three-Dimensional Nonreacting Inviscid Flows in an Internal Combustion Engine

1979 ◽  
Vol 101 (3) ◽  
pp. 367-372 ◽  
Author(s):  
M. D. Griffin ◽  
J. D. Anderson ◽  
E. Jones
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Internal Combustion ◽  
Computational Method ◽  
Striking Similarity ◽  
Stroke Cycle

The three-dimensional inviscid flowfield between the face of the piston and the top of the cylinder in a reciprocating internal combustion engine is calculated for a complete four-stroke cycle (intake, compression, power, exhaust). The fluid dynamic aspects are emphasized; combustion is simply modeled by constant-volume heat addition. The computational method is an explicit time-dependent finite-difference solution of the governing fluid dynamic equations. The results show that a well-defined three-dimensional swirling flow pattern is established during the intake stroke, and that this swirl persists throughout the complete four-stroke cycle. Such a flowfield will have direct influence on I.C. engine combustion phenomena. Moreover, the radial distributions of pressure and temperature show a nearly-axisymmetric behavior, while the three-dimensional results in the valve plane show a striking similarity to previous two-dimensional results. The present investigation is the first three-dimensional calculation of the flowfield for all four strokes, and has important implications for future work in the application of computational fluid dynamics to I. C. engine analysis.

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