scholarly journals Propulsion Mechanism of Flexible Microbead Swimmers in the Low Reynolds Number Regime

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1107
Author(s):  
Yan-Hom Li ◽  
Shao-Chun Chen
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Oscillation Amplitude ◽  
Propulsion Mechanism ◽  
Swimming Efficiency ◽  
Flexible Mechanism ◽  
Low Reynolds ◽  
Different Diameters ◽  
Bending Wave ◽  
Period Of Oscillation

A propulsion mechanism for a flexible microswimmer constructed from superparamagnetic microbeads with different diameters and subjected to an oscillating field was studied experimentally and theoretically herein. Various types of artificial swimmers with different bending patterns were fabricated to determine the flexibility and an effective waveform for a planar beating flagellum. Waveform evolutions for various swimmer configurations were studied to determine the flexible mechanism of the swimmers. A one-armed microswimmer can propel itself only if the friction of its wavelike body is anisotropic. A swimmer with a larger head and a stronger magnetic dipole moment with a flexible tail allows the bending wave to propagate from the head toward the tail to generate forward thrust. The oscillating head and tail do not simultaneously generate positive thrust all the time within a period of oscillation. To increase the propulsion for a bending swimmer, this study proposes a novel configuration for a microbead swimmer that ensures better swimming efficiency. The ratio of the oscillation amplitude of the head to the length of the swimmer (from 0.26 to 0.28) produces a faster swimmer. On the other hand, the swimmer is propelled more effectively if the ratio of the oscillation amplitude of the tail to the length of the swimmer is from 0.29 to 0.33. This study determined the optimal configuration for a flexible microbead swimmer that generates the greatest propulsion in a low Reynolds number environment.

scholarly journals Numerical Simulation of a Pitching Airfoil Under Dynamic Stall of Low Reynolds Number Flow

2019 ◽  
Author(s):  
Mojtaba Honarmand ◽  
Mohammad Hassan Djavareshkian ◽  
Behzad Forouzi Feshalami ◽  
Esmaeil Esmaeilifar
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Aerodynamic Force ◽  
Low Reynolds Number ◽  
Oscillation Amplitude ◽  
Dynamic Stall ◽  
Aerodynamic Forces ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Low Reynolds

In this research, viscous, unsteady and turbulent fluid flow is simulated numerically around a pitching NACA0012 airfoil in the dynamic stall area. The Navier-Stokes equations are discretized based on the finite volume method and are solved by the PIMPLE algorithm in the open source software, namely OpenFOAM. The SST k - ω model is used as the turbulence model for Low Reynolds Number flows in the order of 105. A homogenous dynamic mesh is used to reduce cell skewness of mesh to prevent non-physical oscillations in aerodynamic forces unlike previous studies. In this paper, the effects of Reynolds number, reduced frequency, oscillation amplitude and airfoil thickness on aerodynamic force coefficients and dynamic stall delay are investigated. These parameters have a significant impact on the maximum lift, drag, the ratio of aerodynamic forces and the location of dynamic stall. The most important parameters that affect the maximum lift to drag coefficient ratio and cause dynamic stall delaying are airfoil thickness and reduced frequency, respectively.

Bi-stable flow around tandem cylinders of different diameters at low Reynolds number

2011 ◽  
Vol 43 (5) ◽  
pp. 055506 ◽  
Author(s):  
Yangyang Gao ◽  
Stéphane Etienne ◽  
Dingyong Yu ◽  
Xikun Wang ◽  
Soonkeat Tan
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Tandem Cylinders ◽  
Low Reynolds ◽  
Different Diameters ◽  
Stable Flow

Simulation of dynamic stall using direct-forcing immersed boundary method at low Reynolds number

2018 ◽  
Vol 90 (5) ◽  
pp. 869-876 ◽  
Author(s):  
Nima Vaziri ◽  
Ming-Jyh Chern ◽  
Tzyy-Leng Horng
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Oscillation Amplitude ◽  
Dynamic Stall ◽  
Immersed Boundary ◽  
Ray Casting ◽  
Content Type ◽  
Reduced Frequency ◽  
Direct Forcing ◽  
Low Reynolds

Purpose The purpose of this study is simulation of dynamic stall behavior around the Eppler 387 airfoil in the low Reynolds number flow with a direct-forcing immersed boundary (DFIB) numerical model. Design/methodology/approach A ray-casting method is used to define the airfoil geometry. The governing continuity and Navier–Stokes momentum equations and boundary conditions are solved using the DFIB method. Findings The purposed method is validated against numerical results from alternative schemes and experimental data on static and oscillating airfoil. A base flow regime and different vortices patterns are observed, in accordance with other previously published investigations. Also, the effects of the reduced frequency, the pitch oscillation amplitude and the Reynolds number are studied. The results show that the reduced frequency has a major effect on the flow field and the force coefficients of the airfoil. On the other hand, the Reynolds number of the flow has a little effect on the dynamic stall characteristics of the airfoil at least in the laminar range. Practical implications It is demonstrated that the DFIB model provides an accurate representation of dynamic stall phenomenon. Originality/value The results show that the dynamic stall behavior around the Eppler 387 is different than the general dynamic stall behavior understanding in the shedding phase.

Experimental Investigation on Blunt-Edged UTM Delta Wing VFE-2 Configurations at Low Reynolds Number

2018 ◽  
Vol 12 (3) ◽  
pp. 255
Author(s):  
Muhammad Zal Aminullah Daman Huri ◽  
Shabudin Bin Mat ◽  
Mazuriah Said ◽  
Shuhaimi Mansor ◽  
Md. Nizam Dahalan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Low Reynolds
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