Prediction of Interfacial Positions in Steady Converging Microchannel Flows at Low Reynolds Numbers

2002 ◽  
Author(s):  
T. R. Harris ◽  
D. L. Hitt ◽  
N. Macken
Keyword(s):  
Reynolds Numbers ◽  
Computational Effort ◽  
Planar Interface ◽  
Analytical Models ◽  
Experimental Measurements ◽  
Low Reynolds Numbers ◽  
Analytical Results ◽  
Microchannel Flows ◽  
Low Reynolds ◽  
Good Agreement

Previous work has shown that interfaces formed in steady, converging microchannel flows tend to be planar in nature under a wide variety of MEMS-relevant conditions. Assuming a planar interface, we have developed analytical models to predict the interfacial location in the outlet branch. The analytical results show good agreement with 3-D computational cases and experimental measurements. Application of this analytical, planar interface method represents a significant degrease in computational effort when compared to using CFD to determine interfacial positions.

A Simplified Model for Determining Interfacial Position in Convergent Microchannel Flows

2004 ◽  
Vol 126 (5) ◽  
pp. 758-767 ◽  
Author(s):  
D. L. Hitt ◽  
N. Macken
Keyword(s):  
Cross Sections ◽  
Analytical Framework ◽  
Computational Effort ◽  
Planar Interface ◽  
Computational Studies ◽  
Flow Ratio ◽  
Blood Flows ◽  
Microchannel Flows ◽  
Flow Inertia ◽  
Good Agreement

Previous experimental and computational studies have indicated that interfaces formed in steady, converging microchannel flows with similar liquids tend to be planar in nature under a variety of conditions relevant to micro-scale flows, including MEMS/microfluidic devices and even microcirculatory blood flows. Assuming a planar interface, we have developed an analytical framework to predict the fully developed interfacial location downstream of a convergence of identical microchannels. Results have been obtained for microchannels having rectangular, elliptical/circular and triangular cross-sections as a function of the inlet flow ratio. Two-dimensional results have also been obtained for fluids having unequal viscosities. Good agreement is found between this model and 3-D numerical simulations and experimental measurements provided that the flow inertia remains sufficiently small (Re≲10, typically). Where valid, application of this analytical, planar interface method represents a significant decrease in computational effort when compared to using CFD to determine interfacial positions.

A Planar Micromixer Based on Sequential Logarithmic Spirals

2012 ◽  
Author(s):  
Thomas F. Scherr ◽  
Christian Quitadamo ◽  
Preston Tesvich ◽  
Daniel Sang-Won Park ◽  
Terrence Tiersch ◽  
...  
Keyword(s):  
Time Scale ◽  
Reynolds Numbers ◽  
Diffusive Transport ◽  
Low Reynolds Numbers ◽  
Micro Scale ◽  
Natural Time ◽  
Logarithmic Spirals ◽  
Microchannel Flows ◽  
Low Reynolds ◽  
Made In

Despite the advances made in recent years, mixing on the micro-scale remains a challenge. In typical microchannel flows, the lack of turbulence, evidenced by very low Reynolds numbers, constrains mixing to the natural time scale of diffusion. Peclet numbers, defined as the ratio of convective to diffusive transport, are typically very large in microfluidic applications, where transport is dominated by convection. As a result, a dedicated micromixing element is an integral part of most BioMEMS devices [1].

scholarly journals Film flow over strongly undulated bottom profiles at low Reynolds numbers - Analytical results

PAMM ◽  
2003 ◽  
Vol 2 (1) ◽  
pp. 330-331
Author(s):  
Markus Scholle ◽  
Andreas Wierschem ◽  
Nuri Aksel
Keyword(s):  
Film Flow ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Analytical Results ◽  
Low Reynolds

Heat transfer from a sphere at low Reynolds numbers

1973 ◽  
Vol 60 (2) ◽  
pp. 273-283 ◽  
Author(s):  
S. C. R. Dennis ◽  
J. D. A. Walker ◽  
J. D. Hudson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Viscous Incompressible Fluid ◽  
Reynolds Numbers ◽  
Experimental Measurements ◽  
Low Reynolds Numbers ◽  
Nusselt Numbers ◽  
The Mean ◽  
Low Reynolds ◽  
Prandtl Numbers

The heat transfer due to forced convection from an isothermal sphere in a steady stream of viscous incompressible fluid is calculated for low values of the Reynolds number and Prandtl numbers ofO(1). The mean Nusselt number is compared with the results of experimental measurements. At very low Reynolds numbers, both the local and mean Nusselt numbers are compared with the results obtained from the theory of matched asymptotic expansions.

Measurements of velocity distributions in the wake of a circular cylinder at low Reynolds numbers

1974 ◽  
Vol 65 (1) ◽  
pp. 97-112 ◽  
Author(s):  
Michio Nishioka ◽  
Hiroshi Sato
Keyword(s):  
Circular Cylinder ◽  
Velocity Distribution ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Velocity Measurements ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
High Reynolds ◽  
Good Agreement ◽  
Made In

Velocity measurements were made in the flow field behind a circular cylinder at Reynolds numbers from 10 to 80 and results compared with existing numerical solutions. Takami & Keller's solution for the velocity distribution in the wake shows good agreement at low Reynolds numbers and fair agreement at high Reynolds numbers. The drag coefficient of the cylinder and the size of the standing eddies behind the cylinder were also determined. They are compatible with existing experimental and numerical results. Details of the velocity distribution in the standing eddies are clarified.

scholarly journals Metachronal patterns in artificial cilia for low Reynolds number fluid propulsion

2020 ◽  
Vol 6 (49) ◽  
pp. eabd2508
Author(s):  
Edoardo Milana ◽  
Rongjing Zhang ◽  
Maria Rosaria Vetrano ◽  
Sam Peerlinck ◽  
Michael De Volder ◽  
...  
Keyword(s):  
Phase Shift ◽  
Experimental Tests ◽  
Reynolds Numbers ◽  
Flow Speed ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Dynamics Simulations ◽  
And Control ◽  
Metachronal Waves ◽  
Good Agreement

Cilia are hair-like organelles, present in arrays that collectively beat to generate flow. Given their small size and consequent low Reynolds numbers, asymmetric motions are necessary to create a net flow. Here, we developed an array of six soft robotic cilia, which are individually addressable, to both mimic nature’s symmetry-breaking mechanisms and control asymmetries to study their influence on fluid propulsion. Our experimental tests are corroborated with fluid dynamics simulations, where we find a good agreement between both and show how the kymographs of the flow are related to the phase shift of the metachronal waves. Compared to synchronous beating, we report a 50% increase of net flow speed when cilia move in an antiplectic wave with phase shift of −π/3 and a decrease for symplectic waves. Furthermore, we observe the formation of traveling vortices in the direction of the wave when metachrony is applied.

Investigation on the effect of leading edge tubercles of sweptback wing at low reynolds number

2020 ◽  
Vol 21 (6) ◽  
pp. 621
Author(s):  
Veerapathiran Thangaraj Gopinathan ◽  
John Bruce Ralphin Rose ◽  
Mohanram Surya
Keyword(s):  
Leading Edge ◽  
Reynolds Numbers ◽  
Sweep Angle ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Flow Energy ◽  
Airplane Wing ◽  
Low Reynolds ◽  
Naca 0015 ◽  
Wing Performance

Aerodynamic efficiency of an airplane wing can be improved either by increasing its lift generation tendency or by reducing the drag. Recently, Bio-inspired designs have been received greater attention for the geometric modifications of airplane wings. One of the bio-inspired designs contains sinusoidal Humpback Whale (HW) tubercles, i.e., protuberances exist at the wing leading edge (LE). The tubercles have excellent flow control characteristics at low Reynolds numbers. The present work describes about the effect of tubercles on swept back wing performance at various Angle of Attack (AoA). NACA 0015 and NACA 4415 airfoils are used for swept back wing design with sweep angle about 30°. The modified wings (HUMP 0015 A, HUMP 0015 B, HUMP 4415 A, HUMP 4415 B) are designed with two amplitude to wavelength ratios (η) of 0.1 & 0.24 for the performance analysis. It is a novel effort to analyze the tubercle vortices along the span that induce additional flow energy especially, behind the tubercles peak and trough region. Subsequently, Co-efficient of Lift (CL), Co-efficient of Drag (CD) and boundary layer pressure gradients also predicted for modified and baseline (smooth LE) models in the pre & post-stall regimes. It was observed that the tubercles increase the performance of swept back wings by the enhanced CL/CD ratio in the pre-stall AoA region. Interestingly, the flow separation region behind the centerline of tubercles and formation of Laminar Separation Bubbles (LSB) were asymmetric because of the sweep.

Low Reynolds number flow around and heat transfer from a heated circular cylinder

2010 ◽  
Vol 1 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
B. Bolló
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Increasing Temperature

Abstract The two-dimensional flow around a stationary heated circular cylinder at low Reynolds numbers of 50 < Re < 210 is investigated numerically using the FLUENT commercial software package. The dimensionless vortex shedding frequency (St) reduces with increasing temperature at a given Reynolds number. The effective temperature concept was used and St-Re data were successfully transformed to the St-Reeff curve. Comparisons include root-mean-square values of the lift coefficient and Nusselt number. The results agree well with available data in the literature.

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