Modeling and Numerical Simulation of Flow Resistance Characteristics in Slowly-Varying Rectangular Cross-Section Microchannel

2016 ◽  
Author(s):  
Shen Teng ◽  
Wang Jiong ◽  
Sun Dong ◽  
Liu Yafeng ◽  
Tian Zhouyu
Keyword(s):  
Numerical Simulation ◽  
Theoretical Calculation ◽  
Cross Section ◽  
Flow Resistance ◽  
Rectangular Cross Section ◽  
Flow Characteristics ◽  
Aspect Ratios ◽  
Good Accord ◽  
Simulation Results ◽  
Poiseuille Number

In this paper, flow characteristics in slowly-varying rectangular microchannels with different aspect ratios and Re numbers ranging from 7 to 200 are investigated. The obtained simulation results are compared with theoretics values based on the Bernoulli equations. The results show that the simulation results just hold an average discrepancy of 10% with the theoretical calculation value whichis presents a good accord. All the research of microchannel, the Poiseuille number of the flow is inconstant within the range of Re number, except when the contract angle is small where Poiseuille number is essentially unchanged.

scholarly journals Hydrodynamic Entrance Length for Laminar Flow in Microchannels with Rectangular Cross Section

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 240
Author(s):  
Germán Ferreira ◽  
Artur Sucena ◽  
Luís L. Ferrás ◽  
Fernando T. Pinho ◽  
Alexandre M. Afonso
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Creeping Flow ◽  
Low Reynolds Numbers ◽  
Viscous Forces ◽  
Aspect Ratios ◽  
Judicious Choice ◽  
Microsystem Design

This work presents a detailed numerical investigation on the required development length (L=L/B) in laminar Newtonian fluid flow in microchannels with rectangular cross section and different aspect ratios (AR). The advent of new microfluidic technologies shifted the practical Reynolds numbers (Re) to the range of unitary (and even lower) orders of magnitude, i.e., creeping flow conditions. Therefore, accurate estimations of L at Re≤O(1) are important for microsystem design. At such low Reynolds numbers, in which inertial forces are less dominant than viscous forces, flow characteristics become necessarily different from those at the macroscale where Re is typically much larger. A judicious choice of mesh refinement and adequate numerical methods allowed obtaining accurate results and a general correlation for estimating L, valid in the ranges 0≤Re≤2000 and 0.1≤AR≤1, thus covering applications in both macro and microfluidics.

Heat Transfer for Laminar Flow in Spiral Ducts of Rectangular Cross Section

2005 ◽  
Vol 127 (3) ◽  
pp. 352-356 ◽  
Author(s):  
Michael W. Egner ◽  
Louis C. Burmeister
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Aspect Ratios ◽  
Small Pitch

Laminar flow and heat transfer in three-dimensional spiral ducts of rectangular cross section with aspect ratios of 1, 4, and 8 were determined by making use of the FLUENT computational fluid dynamics program. The peripherally averaged Nusselt number is presented as a function of distance from the inlet and of the Dean number. Fully developed values of the Nusselt number for a constant-radius-of-curvature duct, either toroidal or helical with small pitch, can be used to predict those quantities for the spiral duct in postentry regions. These results are applicable to spiral-plate heat exchangers.

Flow Field Model Experiment Studies of a Bipolar Plates PEMFC

2013 ◽  
Vol 291-294 ◽  
pp. 581-584
Author(s):  
Bing Kun Jiang ◽  
Xin Jie Ji ◽  
Yong Zhong Li
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Field Model ◽  
Flow Distribution ◽  
Flow Channel ◽  
Bipolar Plates ◽  
Gas Utilization ◽  
Section Shape ◽  
Simulation Results ◽  
Gas Supply

The mode experiment is respectively done under condition of different amount of gas supply, different shape of gas admission room, different cross-section shape of flow channel. Results show that pressure descend of U shape cross-section slot is smaller than the rectangle cross-section slot in the equal fault stream section situation, so flow distribution characteristic of U shape cross-section slot is better. The experiment results are consistent with numerical simulation results. In addition, numerical simulation results also indicate that the mass of gas diffusing from U shape cross-section slot to the diffusion layer is over greater, and U shape cross-section flow channel has a higher gas utilization ratio.

Secondary Flow and Hydraulic Losses Within Sinuous Conduits of Rectangular Cross Section

1992 ◽  
Vol 114 (4) ◽  
pp. 593-600 ◽  
Author(s):  
Yukimaru Shimizu ◽  
Yoshiki Futaki ◽  
C. Samuel Martin
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Flow Patterns ◽  
Geometric Configuration ◽  
Hydraulic Losses ◽  
Aspect Ratios ◽  
Wide Range ◽  
The Relationship

This paper describes the relationship between hydraulic losses and secondary flow within sinuous conduits with complicated bends. It has been found that the nature of secondary flow present in the bends is quite sensitive to the geometric configuration of the bend and the actual aspect ratio of the conduit section. Indeed, many different secondary flow patterns have been found to exist as the bend geometry is altered. A wide range of experiments has been conducted for various aspect ratios of a rectangular conduit with different curvatures.

Linear stability of rectangular cavity flows driven by anti-parallel motion of two facing walls

2002 ◽  
Vol 458 ◽  
pp. 153-180 ◽  
Author(s):  
S. ALBENSOEDER ◽  
H. C. KUHLMANN
Keyword(s):  
Aspect Ratio ◽  
Linear Stability ◽  
Cross Section ◽  
Strain Field ◽  
Rectangular Cross Section ◽  
Small Range ◽  
Critical Mode ◽  
Plane Flow ◽  
Aspect Ratios ◽  
The Cross

The flow in an infinite slab of rectangular cross-section is investigated numerically by a finite volume method. Two facing walls which move parallel to each other with the same velocity, but in opposite directions, drive a plane flow in the cross-section of the slab. A linear stability analysis shows that the two-dimensional flow becomes unstable to different modes, depending on the cross-sectional aspect ratio, when the Reynolds number is increased. The critical mode is found to be stationary for all aspect ratios. When the separation of the moving walls is larger than approximately twice the height of the cavity, the basic flow forms two vortices, each close to one of the moving walls. The instability of this flow is of centrifugal type and similar to that in the classical lid-driven cavity problem with a single moving wall. When the moving walls are sufficiently close to each other (aspect ratio less than 2) the two vortices merge and form an elliptically strained vortex. Owing to the dipolar strain this flow becomes unstable through the elliptic instability. When both moving walls are very close, the finite-length plane-Couette flow becomes unstable by a similar elliptic mechanism near both turning zones. The critical mode produces wide streaks reaching far into the cavity. For a small range of aspect ratios near unity the flow consists of a single vortex. Here, the strain field is dominated by a four-fold symmetry. As a result the instability process is analogous to the instability of a Rankine vortex in an quadripolar strain field, resulting from vortex stretching into the four corners of the cavity.

Numerical Simulation of the Effects of Baffle on Flow Field in a Stirred Tank

2013 ◽  
Vol 732-733 ◽  
pp. 432-435 ◽  
Author(s):  
Zong Rui Hao ◽  
Juan Xu ◽  
Hai Yan Bie ◽  
Zhong Hai Zhou
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Cross Section ◽  
Flow Model ◽  
Flow Characteristics ◽  
Stirred Tank ◽  
Stirred Tanks ◽  
Double Peak ◽  
Blade Area ◽  
Radial Circulation

Flow characteristics of stirred tanks with different structures were calculated by taking RNG k-ε model as the turbulent flow model. The results showed that at the same rotational speed, a large number of axial and radial vortexes were formed in the stirred tank with the baffle. The velocity in the blade area was high, and it decreased rapidly with the increasing distance to the blade. The double peak area of the radial velocity was formed in the stirred tank with baffle, and the high and low speed cycles were obtained in the cross-section. The baffle increased not only the axial circulation of the liquid in the tank but also the radial circulation, which help to mix the liquid.

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