scholarly journals Soft Matter Emerging Investigators Issue 2021 - "Propulsion of an elastic filament in a shear-thinning fluid at low Reynolds numbers"

Soft Matter ◽  
2021 ◽  
Author(s):  
Ke Qin ◽  
Zhiwei Peng ◽  
Ye Chen ◽  
Herve Nganguia ◽  
Lailai Zhu ◽  
...  
Keyword(s):  
Soft Matter ◽  
Reynolds Numbers ◽  
Shear Thinning ◽  
Low Reynolds Numbers ◽  
Elastic Filament ◽  
Low Reynolds ◽  
Micro Organisms ◽  
Surrounding Fluid ◽  
Shear Thinning Fluid ◽  
Flexible Appendages

Some micro-organisms and artificial micro-swimmers propel at low Reynolds numbers (Re) via the interaction of their flexible appendages with the surrounding fluid. While their locomotion have been extensively studied with...

scholarly journals Squirming through shear-thinning fluids

2015 ◽  
Vol 784 ◽  
Author(s):  
Charu Datt ◽  
Lailai Zhu ◽  
Gwynn J. Elfring ◽  
On Shun Pak
Keyword(s):  
Asymptotic Analysis ◽  
Numerical Simulations ◽  
Rheological Properties ◽  
Reynolds Numbers ◽  
Shear Thinning ◽  
Fundamental Question ◽  
Low Reynolds Numbers ◽  
Shear Thinning Fluids ◽  
Micro Organisms ◽  
Shear Thinning Fluid

Many micro-organisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in non-trivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problematic.

A Heat Transfer Comparison Between a Synthetic Jet and a Steady Jet at Low Reynolds Numbers

2008 ◽  
Author(s):  
Rayhaan Farrelly ◽  
Alan McGuinn ◽  
Tim Persoons ◽  
Darina B. Murray
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Stroke Length ◽  
Low Reynolds Numbers ◽  
Nusselt Numbers ◽  
Significant Difference ◽  
Low Reynolds ◽  
Surrounding Fluid

A study has been carried out to compare steady jet and synthetic jet heat transfer distributions at low Reynolds numbers. Both jets issued from a 5mm diameter orifice plate with air for the steady jet being supplied by a compressor via a plenum chamber. Tests were conducted for Reynolds numbers ranging from 1000 to 4000, and for non-dimensional surface to jet exit spacings (H/D) from 1 to 6. Dimensionless stroke length (Lo/D) for the synthetic jet was held constant at 8. A significant difference was observed between the steady and synthetic jet Nusselt numbers at low Reynolds numbers and low H/D. In comparison to steady jets, the stronger entrainment of surrounding fluid and the vigorous mixing near the impingement surface are characteristics of synthetic jets that are beneficial to heat transfer. Nonetheless, the steady jet yields higher Nusselt numbers for all test conditions.

Towards a Multi-Flagella Architecture for E.coli Inspired Swimming Microrobot Propulsion

2008 ◽  
Author(s):  
Arash Taheri ◽  
Meysam Mohammadi-Amin
Keyword(s):  
Escherichia Coli ◽  
Reynolds Numbers ◽  
Helical Motion ◽  
Mesoscopic Scale ◽  
Low Reynolds Numbers ◽  
Left Handed ◽  
Low Reynolds ◽  
Localized Drug Delivery ◽  
Micro Organisms ◽  
Flow Inertia

One of the primary goals of medical micro and nano robots is to reach currently inaccessible areas of the human body and carry out a host of complex operations, such as minimally invasive surgery (MIS), highly localized drug delivery, and screening for diseases at their very early stages. One of the innovative approaches to design microrobot propulsion is based on the flagellar motion of bacteria [1]. Certain bacteria, such as Escherichia coli (E.coli) use multiple flagella often concentrated at one end of their bodies to induce locomotion. Each flagellum is formed in a left-handed helix and has a motor at the base that rotates the flagellum in a corkscrew motion. As pointed out by Purcell in his Lecture “Life at low Reynolds numbers” [2], microorganisms experience an environment quite different from our own. In particular, because of their small size (of the order of microns), inertia is, to them, essentially irrelevant. The fact that inertia is irrelevant for micro-organisms makes it difficult for them to move. The propulsive mechanisms based on flow inertia will not work on a mesoscopic scale. To overcome this problem, organisms living in low Reynolds number regimes have developed moving organelles which have a handedness to them. For instance, E. Coli’s flagella rotate with a helical motion, much like a corkscrew. This configuration produces patterns of motion that do not repeat the first half of the cycle in reverse for the second half, allowing the organisms to achieve movement in their environment.

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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