Numerical Study on Fluid Transport and Mixing by Electrothermal Flow in a Microchannel

2019 ◽  
Vol 43 (8) ◽  
pp. 565-578
Author(s):  
Jae-Sung Kwon ◽  
Minsub Han ◽  
Young-Eun Yun
Keyword(s):  
Fluid Transport ◽  
Numerical Study ◽  
Transport And Mixing ◽  
Electrothermal Flow

scholarly journals Mixing and transport by ciliary carpets: a numerical study

2014 ◽  
Vol 743 ◽  
pp. 124-140 ◽  
Author(s):  
Yang Ding ◽  
Janna C. Nawroth ◽  
Margaret J. McFall-Ngai ◽  
Eva Kanso
Keyword(s):  
Fluid Transport ◽  
Numerical Study ◽  
Mixing Time ◽  
Three Dimensional ◽  
Chemical Diffusion ◽  
Metachronal Wave ◽  
Mixing Rates ◽  
Infinite Array ◽  
Transport Region ◽  
Transport And Mixing

AbstractWe use a three-dimensional computational model to study the fluid transport and mixing due to the beating of an infinite array of cilia. In accord with recent experiments, we observe two distinct regions: a fluid transport region above the cilia and a fluid mixing region below the cilia tip. The metachronal wave due to phase differences between neighbouring cilia is known to enhance the fluid transport above the ciliary tip. In this work, we show that the metachronal wave also enhances the mixing rates in the sub-ciliary region, often simultaneously with the flow rate enhancement. Our results suggest that this simultaneous enhancement in transport and mixing is due to an enhancement in shear flow. As the flow above the cilia increases, the shear rate in the fluid increases and this shear enhances stretching, which is an essential ingredient for mixing. Estimates of the mixing time scale indicate that, compared to diffusion, the mixing due to the cilia beat may be significant and sometimes dominates chemical diffusion.

Numerical Study on the Performance of a Tube With Inserted Porous Media of Various Thermal Conductivities

2016 ◽  
Author(s):  
Tariq Amin Khan ◽  
Wei Li
Keyword(s):  
Thermal Conductivity ◽  
Porous Medium ◽  
Porous Media ◽  
Velocity Profile ◽  
Fluid Transport ◽  
Energy Transport ◽  
Numerical Study ◽  
Darcy Number ◽  
Local Thermal Equilibrium ◽  
Working Fluid

Numerical study is performed on the effect of thermal conductivity of porous media (k) on the Nusselt number (Nu) and performance evaluation criteria (PEC) of a tube. Two-dimensional axisymmetric forced laminar and fully developed flow is assumed. Porous medium partially inserted in the core of a tube is investigated under varied Darcy number (Da), i.e., 10−6 ≤ Da ≤ 10−2. The range of Re number used is 100 to 2000 and the conductivity of porous medium is 1.4 to 202.4 W/(m.K) with air as the working fluid. The momentum equations are used to describe the fluid flow in the clear region. The Darcy-Forchheimer-Brinkman model is adopted for the fluid transport in the porous region. The mathematical model for energy transport is based on the one equation model which assumes a local thermal equilibrium between the fluid and the solid phases. Results are different from the conventional thoughts that porous media of higher thermal conductivity can enhance the performance (PEC) of a tube. Due to partial porous media insertion, the upstream parabolic velocity profile is destroyed and the flow is redistributed to create a new fully develop velocity profile downstream. The length of this flow redistribution to a new developed laminar flow depends on the Da number and the hydrodynamic developing length increases with increasing Da number. Moreover, the temperature profile is also readjusted within the tube. The Nu and PEC numbers have a nonlinear trend with varying k. At very low Da number and at a lower k, the Nu number decreases with increasing Re number while at higher k, the Nu number first increases to reach its peak value and then decreases. At higher Re number, the results are independent of k. However, at a higher Da number, the Nu and PEC numbers significantly increases at low Re number while slightly increases at higher Re number. Hence, the change in Nu and PEC numbers neither increases monotonically with k, nor with Re number. Investigation of PEC number shows that at very low Da number (Da = 10−6), inserting porous media of a low k is effective at low Re number (Re ≤ 500) while at high Re number, using porous material is not effective for the overall performance of a tube. However, at a relatively higher Da number (Da = 10−2), high k can be effective at higher Re number. Moreover, it is found that the results are not very sensitive to the inertia term at lower Da number.

Paper-PDMS hybrid microchannel: a platform for rapid fluid-transport and mixing

2016 ◽  
Vol 26 (10) ◽  
pp. 105008 ◽  
Author(s):  
Ravi Kumar Arun ◽  
Nivedita Priyadarshini ◽  
Kaustav Chaudhury ◽  
Nripen Chanda ◽  
Gautam Biswas ◽  
...  
Keyword(s):  
Fluid Transport ◽  
Transport And Mixing

scholarly journals A continuum model for flow induced by metachronal coordination between beating cilia

2011 ◽  
Vol 684 ◽  
pp. 137-162 ◽  
Author(s):  
Jeanette Hussong ◽  
Wim-Paul Breugem ◽  
Jerry Westerweel
Keyword(s):  
Continuum Model ◽  
Fluid Transport ◽  
Numerical Study ◽  
Plane Channel ◽  
Spatial Variations ◽  
Design Tool ◽  
Correct Prediction ◽  
Parameter Study ◽  
Efficient Design ◽  
Metachronal Wave

AbstractIn this numerical study we investigate the flow induced by metachronal coordination between beating cilia arranged in a densely packed layer by means of a continuum model. The continuum approach allows us to treat the problem as two-dimensional as well as stationary, in a reference frame moving with the speed of the metachronal wave. The model is used as a computationally efficient design tool to investigate cilia-induced transport of a Newtonian fluid in a plane channel. Contrary to prior continuum models, the present approach accounts for spatial variations in the porosity along the metachronal wave and thus ensures conservation of mass within the cilia layer. Using porous-media theory the governing volume-averaged Navier–Stokes (VANS) equations are derived and closure formulations are given explicitly for the model. This makes it possible to investigate cilia-induced flow with a continuum model in both the viscous regime and the inertial regime. The results show that metachronal coordination can act as a transport mechanism in both regimes. Porosity variations appear to be the key mechanism for correct prediction of the fluid transport in the viscous flow regime. The reason is that spatial variations in the porosity break the symmetry of the drag distribution along the metachronal wave. A new insight that has been gained is that the fluid transport reverses, thus switches from plectic to antiplectic metachronism, for the same cilia beat cycle when the wavespeed is increased such that inertial effects occur. Based on a parameter study, the net transport in the channel is described by a power-law relation of the amplitude, length and speed of the metachronal wave. It is found that the wavelength has the strongest effect on the viscosity-dominated fluid transport.

EFFECTS OF OPERATING CONDITIONS ON THE DEPOSITION OF GaAs IN A VERTICAL CVD REACTOR

2008 ◽  
Vol 15 (01n02) ◽  
pp. 111-116 ◽  
Author(s):  
JAE-SANG BAEK ◽  
JIN-HYO BOO ◽  
YOUN-JEA KIM
Keyword(s):  
Fluid Transport ◽  
Numerical Study ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Rotation Velocity ◽  
Operating Conditions ◽  
Deposition Condition ◽  
Three Dimensional Model ◽  
Trimethyl Gallium ◽  
Vertical Cvd Reactor

A numerical study is needed to gain insight into the growth mechanism and improve the reactor design or optimize the deposition condition in chemical vapor deposition (CVD). In this study, we have performed a numerical analysis of the deposition of gallium arsenide ( GaAs ) from trimethyl gallium (TMG) and arsine in a vertical CVD reactor. The effects of operating parameters, such as the rotation velocity of susceptor, inlet velocity, and inlet TMG fraction, are investigated and presented. The three-dimensional model which is used in this investigation includes complete coupling between the thermal-fluid transport and species transport with chemical reaction.

An Experimental and Numerical Study of Regulating Performance and Flow Loss in a V-Port Ball Valve

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Junyu Tao ◽  
Zhe Lin ◽  
Chuanjing Ma ◽  
Jiahui Ye ◽  
Zuchao Zhu ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Fluid Transport ◽  
Numerical Study ◽  
Internal Flow ◽  
External Pressure ◽  
Ball Valve ◽  
Flow Coefficient ◽  
Design And Optimization ◽  
Stable Position ◽  
Valve Opening

Abstract Process valves are responsible for regulating and controlling the rate and direction of flow in pipeline systems. The V-port ball valve is one kind of process valve with a regulating performance influenced by V-angle. In this article, a DN50 V-port ball valve is taken as the research object. This work therefore aims to investigate the effect of and relationship between the V-angle on valve performance and internal flow properties via experiments and numerical simulations. Results indicate that an increase in either V-angle or valve opening causes a large-pressure fluctuation near the valve outlet, thus leading to a long pressure-stable distance. Meanwhile, the flow coefficient increases exponentially with valve opening, and the value of the exponent remains at 2.5 for different V-angles. Furthermore, the stable position of internal energy loss along the downstream pipe is well-matched with the stable position of external pressure fluctuation. This inspires a new method for controlling the pressure stability downstream from the valve. These results may facilitate improvements in the design and optimization of the process valve, thus benefiting the development of fluid transport techniques in energy industries.

scholarly journals Interaction between Crustal-Scale Darcy and Hydrofracture Fluid Transport: A Numerical Study

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Tamara de Riese ◽  
Paul D. Bons ◽  
Enrique Gomez-Rivas ◽  
Till Sachau
Keyword(s):  
Fluid Flow ◽  
Numerical Model ◽  
Transport Mechanism ◽  
Large Scale ◽  
Fluid Transport ◽  
Numerical Study ◽  
Ballistic Transport ◽  
Accretionary Prism ◽  
Small Scale ◽  
Porous Flow

Crustal-scale fluid flow can be regarded as a bimodal transport mechanism. At low hydraulic head gradients, fluid flow through rock porosity is slow and can be described as diffusional. Structures such as hydraulic breccias and hydrothermal veins both form when fluid velocities and pressures are high, which can be achieved by localized fluid transport in space and time, via hydrofractures. Hydrofracture propagation and simultaneous fluid flow can be regarded as a “ballistic” transport mechanism, which is activated when transport by diffusion alone is insufficient to release the local fluid overpressure. The activation of a ballistic system locally reduces the driving force, through allowing the escape of fluid. We use a numerical model to investigate the properties of the two transport modes in general and the transition between them in particular. We developed a numerical model in order to study patterns that result from bimodal transport. When hydrofractures are activated due to low permeability relative to fluid flux, many hydrofractures form that do not extend through the whole system. These abundant hydrofractures follow a power-law size distribution. A Hurst factor of ~0.9 indicates that the system self-organizes. The abundant small-scale hydrofractures organize the formation of large-scale hydrofractures that ascend through the whole system and drain fluids in large bursts. As the relative contribution of porous flow increases, escaping fluid bursts become less frequent, but more regular in time and larger in volume. We propose that metamorphic rocks with abundant veins, such as in the Kodiak accretionary prism (Alaska) and Otago schists (New Zealand), represent regions with abundant hydrofractures near the fluid source, while hydrothermal breccias are formed by the large fluid bursts that can ascend the crust to shallower levels.

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