A computational model for heterogeneous flow through low headloss biofilter media

2002 ◽  
Vol 21 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Derek E. Chitwood ◽  
Joseph S. Devinny ◽  
Eckart Meiburg
Keyword(s):  
Computational Model ◽  
Heterogeneous Flow ◽  
Flow Through

Signature of coalescence during scalar mixing in heterogeneous flow fields

2020 ◽  
Author(s):  
Sabyasachi Sen ◽  
Prajwal Singh ◽  
Joris Heyman ◽  
Tanguy Le Borgne ◽  
Aditya Bandopadhyay
Keyword(s):  
Porous Media ◽  
Fluid Mechanics ◽  
Large Scale ◽  
Scalar Fields ◽  
Flow Fields ◽  
Scalar Mixing ◽  
Heterogeneous Flow ◽  
Strip Method ◽  
Mixing Rates ◽  
Flow Through

<p>Stretching of fluid elements by a heterogeneous flow field, such as the flow through a porous media or geophysical flows such as atmospheric or oceanic vortices, is known to enhance mixing rates of scalar fields[1]. While the mechanisms leading to the elongation of material lines are well understood, predicting mixing rates still remains a challenge particularly when there is a reconnection (or aggregation) between several parts of the mixing interface, leading, at large mixing time, to a so-called coalescence regime[1][2]. In this presentation, we numerically study this coalescence dynamics through scalar transport in two different flow fields, the Rankine vortex and Stokes flow through a periodic bead pack[3]. The former is typical of large-scale turbulent flows [4] whereas the second is generic of small-scale laminar flows in porous media [5]. Both flows show a net elongation of the mixing interfaces, although at very different rates. To solve the transport problem in these flows, we use a Lagrangian method (the diffusive strip method[6]). This method allows us to reconstruct, at high resolution, the scalar concentration fields and to compute the evolution of the distribution of concentrations levels, scalar dissipation rate and scalar power spectrum in time. The signature of coalescence is clearly observed in both flows and we assess the influence of coalescence on the difference in mixing behaviour for the two flows. We finally discuss how coalescence may affect the reaction kinetics of mixing-limited reactive flows. The analysis proposed sheds light on fundamental aspects of transport and mixing in earth surface and subsurface flows.</p><p>[1] Emmanuel Villermaux. Mixing versus stirring. Annual Review of Fluid Mechanics, 51:245–273, 2019.<br>[2] Tanguy Le Borgne, Marco Dentz, and Emmanuel Villermaux. The lamellar description of mixing in porous media. Journal of Fluid Mechanics, 770:458–498, 2015.<br>[3] Régis Turuban, David R Lester, Tanguy Le Borgne, and Yves Méheust. Space-group symmetries generate chaotic fluid advection in crystalline granular media. Physical review letters, 120(2):024501, 2018.<br>[4] RT Pierrehumbert. Large-scale horizontal mixing in planetary atmospheres. Physics of Fluids A: Fluid Dynamics, 3(5):1250–1260, 1991.<br>[5] Brian Berkowitz, Andrea Cortis, Marco Dentz, and Harvey Scher. Modeling non-fickian transport in geological formations as a continuous time random walk. Reviews of Geophysics, 44(2), 2006.<br>[6] Patrice Meunier and Emmanuel Villermaux. The diffusive strip method for scalar mixing in two dimensions. Journal of fluid mechanics, 662:134–172, 2010.</p>

scholarly journals Variation of Pressure Drop along the Straight and Bifurcated Channel: Experiment and Simulation

2019 ◽  
Vol 8 (12) ◽  
pp. 2728-2731
Keyword(s):  
Pressure Drop ◽  
Laminar Flow ◽  
Aspect Ratio ◽  
Computational Model ◽  
Flow Rate ◽  
Normal Water ◽  
Flow Through ◽  
Experiment And Simulation

This paper derives an experimental and simulated investigation carried to analyze the performance of channel for calculating the pressure drop in laminar flow through rectangular shaped (straight and branched) microchannels. The microchannels taken ranged in variable aspect ratio from 0.75 to 1. Every check piece was made from copper and contained only one channel along a direction. The experiments were conducted with normal water, with Reynolds range starting from some 720 to 3500. Predictions obtained supported that with the variation in the aspect ratio the properties of the fluid also change. It is observed that the pressure drop changes with the change in the aspect ratio and flow rate and found that there is a correlation between the experimental and computational model results.

scholarly journals Effective Computational Framework for Pre-Interventional Planning of Peripheral Arteriovenous Malformations with In Vivo and In Vitro Validation

2021 ◽  
Author(s):  
Gaia Franzetti ◽  
Mirko Bonfanti ◽  
Cyrus Tanade ◽  
Chung Sim Lim ◽  
Janice Tsui ◽  
...  
Keyword(s):  
Blood Flow ◽  
Computational Model ◽  
Arteriovenous Malformations ◽  
Clinical Decision Making ◽  
Patient Specific ◽  
Post Intervention ◽  
Computational Framework ◽  
Mock Circulatory System ◽  
Flow Through

Purpose: Peripheral arteriovenous malformations (pAVMs) are congenital lesions characterised by abnormal high-flow, low-resistance vascular connections - constituting the so-called nidus - between arteries and veins. The mainstay treatment typically involves the embolisation of the nidus with embolic and sclerosant agents, however the complexity of AVMs often leads to uncertain outcomes. This study aims at developing a simple, yet effective computational framework to aid the clinical decision making around the treatment of pAVMs. Methods: A computational model was developed to simulate the pre-, intra-, and post-intervention haemodynamics of an AVM. A porous medium of varying permeability was used to simulate the effect that the sclerosant has on the blood flow through the nidus. The computational model was informed by computed tomography (CT) scans and digital subtraction angiography (DSA) images, and the results were compared against clinical data and experimental results. Results: The computational model was able to simulate the blood flow through the AVM throughout the intervention and predict (direct and indirect) haemodynamic changes due to the embolisation. The simulated transport of the dye in the AVM was compared against DSA time-series obtained at different intervention stages, providing confidence in the results. Moreover, experimental data obtained via a mock circulatory system involving a patient specific 3D printed phantom of the same AVM provided further validation of the simulation results. Conclusion: We developed a simple computational framework to simulate AVM haemodynamics and predict the effects of the embolisation procedure. The developed model lays the foundation of a new, computationally driven treatment planning tool for AVM embolisation procedures.

Distributed Leakage Flow in Raised-Floor Data Centers

2005 ◽  
Author(s):  
Amir Radmehr ◽  
Roger R. Schmidt ◽  
Kailash C. Karki ◽  
Suhas V. Patankar
Keyword(s):  
Computational Model ◽  
Data Center ◽  
Data Centers ◽  
Quantitative Relationship ◽  
Leakage Flow ◽  
Typical Data ◽  
Leakage Area ◽  
Flow Through ◽  
Cooling Air ◽  
Plenum Pressure

In raised-floor data centers, distributed leakage flow—the airflow through seams between panels on the raised floor—reduces the amount of cooling air available at the inlets of the computer equipment. This airflow must be known to determine the total cooling air requirement in a data center. The amount of distributed leakage flow depends on the area of the seams and the plenum pressure, which, in turn, depends on the amount of airflow into the plenum and the total open area (combined area of perforated tiles, cutouts, and seams between panels) on the raised floor. The goal of this study is to outline a procedure to measure leakage flow, to provide data on the amount of the distributed leakage flow, and to show the quantitative relationship between the leakage flow and the leakage area. It also uses a computational model to calculate the distributed leakage flow, the flow through perforated tiles, and the plenum pressure. The results obtained from the model are verified using the measurements. Such a model can be used for design and maintenance of data centers. The measurements show that the leakage flow in a typical data center is between 5–15% of the available cooling air. The measured quantities were used to estimate the area of the seams; for this data center, it was found to be 0.35% of the floor area. The computational model represents the actual physical scenarios very well. The discrepancy between the calculated and measured values of leakage flow, flow through perforated tiles, and plenum pressure is less than 10%.

How countercurrent blood flow and uneven perfusion affect the motion of inert gas

1990 ◽  
Vol 69 (1) ◽  
pp. 162-170 ◽  
Author(s):  
L. D. Homer ◽  
P. K. Weathersby ◽  
S. Survanshi
Keyword(s):  
Mean Transit Time ◽  
High Flow ◽  
Inert Gas ◽  
Low Flow ◽  
Relative Dispersion ◽  
Heterogeneous Flow ◽  
Small Vessels ◽  
Transit Times ◽  
Flow Through ◽  
Washout Curves

Monte Carlo simulations of the passage of inert gas through muscle tissue reveal that countercurrent gas exchange is more important than heterogeneity of flow in determination of the shape of inert gas washout curves. Semilog plots of inert gas washout are usually curved rather than straight. Two explanations often offered are that countercurrent flow may distort the shape and that uneven perfusion of the tissue gives rise to nonuniform washout. The curvature of the semilog plot may be summarized by the relative dispersion (RD), which is the ratio of the standard deviation of transit times to the mean transit time. For straight semilog plots, RD is 1. Semilog plots of data showing xenon washout from dog tissues are curved and have and RD of approximately 2. We have simulated the transit of gas particles through a vascular bed composed of repeating units of 100 mg of tissue perfused by three small vessels 80 microns in diameter and several levels of branching that direct flow through 190,000 capillaries. Geometric distribution of flow is important. Similar degrees of flow heterogeneity affect the curvature of the washout curve more if regions of heterogeneous flow are widely spaced than if they are close together. Diffusion blunts the effects of heterogeneous flow by mixing particles in high-flow regions with particles in low-flow regions. Because of this mixing, alternating regions of high flow and low flow spaced at intervals of less than 0.5 cm are unlikely explanations for the curved semilog plots.(ABSTRACT TRUNCATED AT 250 WORDS)

Modeling flow in collecting lymphatic vessels: one-dimensional flow through a series of contractile elements

2008 ◽  
Vol 295 (1) ◽  
pp. H305-H313 ◽  
Author(s):  
A. J. Macdonald ◽  
K. P. Arkill ◽  
G. R. Tabor ◽  
N. G. McHale ◽  
C. P. Winlove
Keyword(s):  
Computational Model ◽  
Lymphatic System ◽  
Lymphatic Vessels ◽  
Biomechanical Properties ◽  
Dynamic Mechanical Properties ◽  
One Dimensional ◽  
Main Circulation ◽  
Flow Through ◽  
The Individual ◽  
Modeling Flow

The lymphatic system comprises a series of elements, lymphangions, separated by valves and possessed of active, contractile walls to pump interstitial fluid from its collection in the terminal lymphatics back to the main circulation. Despite its importance, there is a dearth of information on the fluid dynamics of the lymphatic system. In this article, we describe linked experimental and computational work aimed at elucidating the biomechanical properties of the individual lymphangions. We measure the static and dynamic mechanical properties of excised bovine collecting lymphatics and develop a one-dimensional computational model of the coupled fluid flow/wall motion. The computational model is able to reproduce the pumping behavior of the real vessel using a simple contraction function producing fast contraction pulses traveling in the retrograde direction to the flow.

Silicate-Enhanced Heterogeneous Flow-Through Electro-Fenton System Using Iron Oxides under Nanoconfinement

2021 ◽  
Author(s):  
Dongli Guo ◽  
Yanbiao Liu ◽  
Haodong Ji ◽  
Chong-Chen Wang ◽  
Bo Chen ◽  
...  
Keyword(s):  
Iron Oxides ◽  
Heterogeneous Flow ◽  
Flow Through ◽  
Fenton System
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