A Multiphase Flow Simulation for a Cells-on-a-Chip Device

2016 ◽  
Author(s):  
Meihua Zhang ◽  
Amy Zheng ◽  
Z. Charlie Zheng ◽  
Zhuo Michael Wang
Keyword(s):  
Fluid Dynamic ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Multiphase Model ◽  
Flow Shear ◽  
Controlled System ◽  
Culture Cells ◽  
Medium Flow ◽  
Chip Geometry

Microfluidics-based microscale cell culture (cells-on-a-chip) provides a well-controlled system with physiological realistic parameters that emulates the organ-to-organ network of the human body. In the microenvironment, the in vivo situation can be resembled closely by controlling the chip geometry, medium flow behavior, medium-to-cell ratio, and other fluid dynamic parameters. This study is to develop a multiphase model to simulate the flow in such a device. The cell deposition rate influenced by the flow shear is discussed. The physics of fluid dynamics for each of the above mentioned parameters is investigated.

scholarly journals Flow Simulation Using Local Grid Refinements to Model Laminated Reservoirs

2018 ◽  
Vol 73 ◽  
pp. 5 ◽  
Author(s):  
Manuel Gomes Correia ◽  
Célio Maschio ◽  
Denis José Schiozer
Keyword(s):  
Simulation Model ◽  
Dynamic Properties ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Coarse Grid ◽  
Thin Layers ◽  
Static Properties ◽  
Dynamic Representation ◽  
Medium Flow ◽  
Local Grid

Super-giant carbonate fields, such as Ghawar, in Saudi Arabia, and Lula, at the Brazilian pre-salt, show highly heterogeneous behavior that is linked to high permeability intervals in thin layers. This article applies Local Grid Refinements (LGR) integrated with upscaling procedures to improve the representation of highly laminated reservoirs in flow simulation by preserving the static properties and dynamic trends from geological model. This work was developed in five main steps: (1) define a conventional coarse grid, (2) define LGR in the conventional coarse grid according to super-k and well locations, (3) apply an upscaling procedure for all scenarios, (4) define LGR directly in the simulation model, without integrate geological trends in LGR and (5) compare the dynamic response for all cases. To check results and compare upscaling matches, was used the benchmark model UNISIM-II-R, a refined model based on a combination of Brazilian Pre-salt and Ghawar field information. The main results show that the upscaling of geological models for coarse grid with LGR in highly permeable thin layers provides a close dynamic representation of geological characterization compared to conventional coarse grid and LGR only near-wells. Pseudo-relative permeability curves should be considered for (a) conventional coarse grid or (b) LGR scenarios under dual-medium flow simulations as the upscaling of discrete fracture networks and dual-medium flow models presents several limitations. The conventional approach of LGR directly in simulation model, presents worse results than LGR integrated with upscaling procedures as the extrapolation of dynamic properties to the coarse block mismatch the dynamic behavior from geological characterization. This work suggests further improvements for results for upscaling procedures that mask the flow behavior in highly laminated reservoirs.

Multiphase flow experiment and simulation for cells-on-a-chip devices

2019 ◽  
Vol 233 (4) ◽  
pp. 432-443 ◽  
Author(s):  
Meihua Zhang ◽  
Amy Zheng ◽  
Zhongquan C Zheng ◽  
Michael Zhuo Wang
Keyword(s):  
Multiphase Flow ◽  
Soft Lithography ◽  
Particle Deposition ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Density Ratio ◽  
Simulation Method ◽  
Quantitative Agreement ◽  
Geometry Model

A microfluidic-based microscale cell-culture device, or a cells-on-a-chip device, provides a well-controlled environment with physiologically realistic factors that emulate the organ-to-organ network of human body. In the microsystem, the in vivo situation can be resembled closely by controlling the chip geometry model, medium flow behavior, medium-to-cell density ratio, and other fluid dynamic parameters. This study is to develop multiphase models to carry out experiments and simulate flow in such devices. A standard soft lithography method is used to build the three-dimensional microfluidic chips. A definitely good qualitative and reasonably good quantitative agreement is obtained between the experimental and simulation results for particle velocity in the microfluidic chip, which validates the numerical simulation method. The cell deposition rate influenced by the flow shear is studied. The influence of gravity, inlet velocity, and cell injection number on cell concentrations are also investigated. Comparisons of different designs of cells-on-a-chip devices are addressed in the study. The physics of flow dynamics and related cell particle motion due to each of the above-mentioned variables are discussed. The results show that the multiphase flow model is promising to be used for simulating cell particle deposition and concentration for the purpose of design of cells-on-a-chip devices.

DIAGNOSTIC AND THERAPEUTIC TREATMENTS OF PLAQUES IN THE CAROTID BIFURCATION — STUDIES IN MODELS WITH STENTS AND FILTERS

2014 ◽  
Vol 14 (03) ◽  
pp. 1450030
Author(s):  
D. LIEPSCH ◽  
A. BALASSO ◽  
C. ZIMMER ◽  
H. BERGER ◽  
R. BURKHART ◽  
...  
Keyword(s):  
Flow Rate ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Carotid Bifurcation ◽  
Flow Rate Ratio ◽  
Shear Stresses ◽  
Dynamic Factors ◽  
Rate Ratios ◽  
Visualization Techniques

Fluid dynamics, especially forces and velocity distribution, influence the development of plaques. Flow parameters: pulsatility, the non-Newtonian flow behavior of blood and wall elasticity are considered. Flow visualization techniques (dyes and birefringent solution with a photo-elasticity apparatus) and LDA measurements demonstrate the importance of the flow. Accurate in vivo velocity measurements are necessary to calculate shear stresses. Different bifurcation angles and flow rate ratios were tested in true to life artery models. The most important fluid dynamic factors at bifurcations are the flow rate ratio and the geometry which create flow separation regions which are responsible for platelet aggregation and intima damage. It is necessary to measure all three velocity components to calculate the velocity vector. The highest shear stresses in a healthy carotid artery are 16 Pa and are found just at the apex. In artery models with 90% stenosis, shear stresses up to 250 Pa were found. Distally, vortices were created where particles remained over several pulse cycles. Measurements show that stents must be selected carefully and placed precisely. Filters must be closed during the systolic phase before removal, so that no trapped particles can escape.

NON-ISOTHERMAL EFFECTS IN PARTIALLY FILLED RUBBER MIXING SIMULATIONS OF MANUFACTURING PROCESSES

2019 ◽  
Vol 92 (1) ◽  
pp. 152-167 ◽  
Author(s):  
Hari Poudyal ◽  
Suma R. Das ◽  
Abhilash J. Chandy
Keyword(s):  
Heat Generation ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Maximum Shear Stress ◽  
Isothermal Flow ◽  
Cumulative Distribution ◽  
Multiphase Model ◽  
Significant Difference ◽  
Distribution Index

ABSTRACT A finite volume technique is used to analyze the isothermal and non-isothermal flow behavior for the rubber mixing process in a two-dimensional, partially filled (75%) internal mixer, which consists of two counterrotating rotors rotating at 20 rpm. In order to capture the interface between air and rubber, an Eulerian multiphase model called volume of fluid (VOF) has been employed here. The transient flow behavior was accomplished by a sliding mesh technique, and the highly viscous, non-Newtonian properties of the rubber have been characterized using the Bird–Carreau model. Most of the previous computational fluid dynamic (CFD)-based investigations of rubber mixing assumed isothermal flow, and consequently negligible viscous heat generation, temperature rise, and viscosity drop associated with heat generation. Hence, a non-isothermal simulation is carried out, and results are compared with those of an equivalent isothermal simulation. In addition, dispersive and distributive mixing characteristics are assessed using statistics calculated from particle tracks generated by a set of massless and neutral particles that have been injected in the simulation. For this purpose, quantities such as the cumulative distribution of maximum shear stress, length of stretch, and cluster distribution index are calculated and compared between isothermal and non-isothermal conditions. Results showed a significant difference between the isothermal and non-isothermal simulations, thus making the isothermal assumption critical. Also, the non-isothermal simulation predicted better mixing during the entire mixing cycle.

scholarly journals Numerical Prediction of a Radial Turbine Performance designed for Automotive Engines Turbocharger

2018 ◽  
Vol 26 (4) ◽  
Author(s):  
Layth H. Jawad
Keyword(s):  
Computational Fluid Dynamic ◽  
Volume Flow Rate ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Flow Simulation ◽  
Flow Dynamics ◽  
Detailed Result ◽  
Turbine Stage ◽  
Radial Turbine

These days the turbocharging system is assuming an essential part in enhancing car engines performance and diminishing fuel utilization and the fumes emanations, in spark-ignition and compression ignition engines. The performance of a radial turbine for the turbocharger device is heavily affected by the flow dynamics in a radial impeller. Furthermore, modification and improvement of a radial turbine impeller is a challenging task for turbomachinery engineers. Hence, this study aimed to further computational fluid dynamic analyses of a radial turbine stage performance .The design characteristics of a radial turbine stage,  was used to simulate the flow by using independent packages of ANSYS CFX. The comparative study of a three dimensional flow simulation will give a more reasonable results of the turbine stage flow behavior and computational fluid dynamic simulation can give a more detailed result and reveal unexpected flow behavior like separation and vortexes.The results showed that the fluid flow dynamics within a turbine stage has indicated a noticeable performance characteristics. Obviously, it was observed that the pressure ratio and volume flow rate and efficiency were predicted numerically. Overall  numerical results obtained from computational fluid dynamic simulations could produce a highly reliable for estimation on the performance a radial turbine of turbocharger.

scholarly journals Internal face finishing for a cooling channel using a fluid containing free abrasive grains

2021 ◽  
Author(s):  
Mitsugu Yamaguchi ◽  
Tatsuaki Furumoto ◽  
Shuuji Inagaki ◽  
Masao Tsuji ◽  
Yoshiki Ochiai ◽  
...  
Keyword(s):  
High Speed ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Cooling Channel ◽  
H13 Steel ◽  
Channel Diameter ◽  
Abrasive Grains ◽  
Low Viscosity ◽  
Short Period ◽  
Internal Pressures

AbstractIn die-casting and injection molding, a conformal cooling channel is applied inside the dies and molds to reduce the cycle time. When the internal face of the channel is rough, both cooling performance and tool life are negatively affected. Many methods for finishing the internal face of such channels have been proposed. However, the effects of the channel diameter on the flow of a low-viscosity finishing media and its finishing characteristics for H13 steel have not yet been reported in the literature. This study addresses these deficiencies through the following: the fluid flow in a channel was computationally simulated; the flow behavior of abrasive grains was observed using a high-speed camera; and the internal face of the channel was finished using the flow of a fluid containing abrasive grains. The flow velocity of the fluid with the abrasive grains increases as the channel diameter decreases, and the velocity gradient is low throughout the channel. This enables reduction in the surface roughness for a short period and ensures uniform finishing in the central region of the channel; however, over polishing occurs owing to the centrifugal force generated in the entrance region, which causes the form accuracy of the channel to partially deteriorate. The outcomes of this study demonstrate that the observational finding for the finishing process is consistent with the flow simulation results. The flow simulation can be instrumental in designing channel diameters and internal pressures to ensure efficient and uniform finishing for such channels.

In vitro and in vivo pathologic effects of Vibrio parahaemolyticus on human epithelial cells

1984 ◽  
Vol 30 (3) ◽  
pp. 381-388 ◽  
Author(s):  
B. R. Merrell ◽  
R. I. Walker ◽  
S. W. Joseph
Keyword(s):  
Epithelial Cells ◽  
Epithelial Tissue ◽  
Ileal Mucosa ◽  
Cytotoxic Factor ◽  
Culture Cells ◽  
Vibrio Parahemolyticus ◽  
Buccal Epithelial Cells ◽  
Culture Supernate

The initial interaction and adherence of Vibrio parahemolyticus to epithelial tissue culture cells, human buccal epithelial cells, and the ileal mucosa of mice were studied. Using scanning electron microscopy, adherent bacteria were observed only on degenerating human embryonic intestinal, HeLa, and buccal cells; healthy normal cells were devoid of bacteria. Sheared V. parahaemolyticus, i.e., lacking flagella, did not adhere to either normal or degenerating tissue cells. Neither ultraviolet-inactivated organisms nor cell-free culture supernate affected the epithelial cells. Similar findings were observed on the mucosa of the ileum in mice inoculated with V. parahaemolyticus. It appears that V. parahaemolyticus possesses a cytotoxic factor which alters epithelial cells. This factor appears to be closely associated with viable organisms and may be a functional element in the adherence process of flagellated V. parahaemolyticus to mammalian epithelial cells.

Flow recirculation zone length and shear rate are differentially affected by stenosis severity in human coronary arteries

2013 ◽  
Vol 304 (4) ◽  
pp. H559-H566 ◽  
Author(s):  
Ashkan Javadzadegan ◽  
Andy S. C. Yong ◽  
Michael Chang ◽  
Austin C. C. Ng ◽  
John Yiannikas ◽  
...  
Keyword(s):  
Shear Rate ◽  
Coronary Arteries ◽  
Recirculation Zone ◽  
Fluid Dynamic ◽  
Zone Length ◽  
Flow Recirculation ◽  
Stenosis Severity ◽  
Recirculation Zones ◽  
The Relationship

Flow recirculation zones and shear rate are associated with distinct pathogenic biological pathways relevant to thrombosis and atherogenesis. The interaction between stenosis severity and lesion eccentricity in determining the length of flow recirculation zones and peak shear rate in human coronary arteries in vivo is unclear. Computational fluid dynamic simulations were performed under resting and hyperemic conditions on computer-generated models and three-dimensional (3-D) reconstructions of coronary arteriograms of 25 patients. Boundary conditions for 3-D reconstructions simulations were obtained by direct measurements using a pressure-temperature sensor guidewire. In the computer-generated models, stenosis severity and lesion eccentricity were strongly associated with recirculation zone length and maximum shear rate. In the 3-D reconstructions, eccentricity increased recirculation zone length and shear rate when lesions of the same stenosis severity were compared. However, across the whole population of coronary lesions, eccentricity did not correlate with recirculation zone length or shear rate ( P = not signficant for both), whereas stenosis severity correlated strongly with both parameters ( r = 0.97, P < 0.001, and r = 0.96, P < 0.001, respectively). Nonlinear regression analyses demonstrated that the relationship between stenosis severity and peak shear was exponential, whereas the relationship between stenosis severity and recirculation zone length was sigmoidal, with an apparent threshold effect, demonstrating a steep increase in recirculation zone length between 40% and 60% diameter stenosis. Increasing stenosis severity and lesion eccentricity can both increase flow recirculation and shear rate in human coronary arteries. Flow recirculation is much more sensitive to mild changes in the severity of intermediate stenoses than is peak shear.

scholarly journals Squeezing Force of the Magnetorheological Fluid Isolating Damper for Centrifugal Fan in Nuclear Power Plant

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Jin Huang ◽  
Ping Wang ◽  
Guochao Wang
Keyword(s):  
Nuclear Power ◽  
Theoretical Foundation ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Magnetorheological Fluid ◽  
Centrifugal Fan ◽  
Parallel Channel ◽  
Mr Fluid ◽  
Mr Fluids ◽  
Control Devices

Magnetorheological (MR) disk-type isolating dampers are the semi-active control devices that use MR fluids to produce controllable squeezing force. In this paper, the analytical endeavor into the fluid dynamic modeling of an MR isolating damper is reported. The velocity and pressure distribution of an MR fluid operating in an axisymmetric squeeze model are analytically solved using a biviscosity constitutive model. Analytical solutions for the flow behavior of MR fluid flowing through the parallel channel are obtained. The equation for the squeezing force is derived to provide the theoretical foundation for the design of the isolating damper. The result shows that with the increase of the applied magnetic field strength, the squeezing force is increased.

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