Steric scattering of rod-like swimmers in low Reynolds number environments

Soft Matter ◽

10.1039/d0sm01551b ◽

2021 ◽

Author(s):

Kentaro Hoeger ◽

Tristan Ursell

Keyword(s):

Reynolds Number ◽

Cell Size ◽

Low Reynolds Number ◽

Surface Curvature ◽

Natural Environments ◽

Solid Objects ◽

Low Reynolds

While navigating natural environments, interactions with cell-size solid objects alter paths of swimming microbes. We characterized such ‘scattering’ from synthetic objects of controlled surface curvature. A sterics-only model agrees well with the data.

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Unsteady swimming of small organisms

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.177 ◽

2012 ◽

Vol 702 ◽

pp. 286-297 ◽

Cited By ~ 40

Author(s):

S. Wang ◽

A. M. Ardekani

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Fundamental Equation ◽

Added Mass ◽

Natural Environments ◽

Mean Velocity ◽

Unsteady Forces ◽

Uniform Background ◽

Low Reynolds

AbstractSmall planktonic organisms ubiquitously display unsteady or impulsive motion to attack a prey or escape a predator in natural environments. Despite this, the role of unsteady forces such as history and added mass forces on the low-Reynolds-number propulsion of small organisms, e.g. Paramecium, is poorly understood. In this paper, we derive the fundamental equation of motion for an organism swimming by means of the surface distortion in a non-uniform background flow field at a low-Reynolds-number regime. We show that the history and added mass forces are important as the product of Reynolds number and Strouhal number increases above unity. Our results for an unsteady squirmer show that unsteady inertial effects can lead to a non-zero mean velocity for the cases with zero streaming parameters, which have zero mean velocity in the absence of inertia.

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Surface curvature effects on the tonal noise performance of a low Reynolds number aerofoil

Applied Acoustics ◽

10.1016/j.apacoust.2017.04.002 ◽

2017 ◽

Vol 125 ◽

pp. 34-40 ◽

Cited By ~ 7

Author(s):

Xiang Shen ◽

Eldad Avital ◽

Qinghe Zhao ◽

Junhui Gao ◽

Xiaodong Li ◽

...

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Surface Curvature ◽

Noise Performance ◽

Tonal Noise ◽

Curvature Effects ◽

Low Reynolds

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Low Reynolds number proprotor aerodynamic performance improvement using the continuous surface curvature design approach

The Aeronautical Journal ◽

10.1017/aer.2018.124 ◽

2018 ◽

Vol 123 (1259) ◽

pp. 20-38

Author(s):

E. J. Avital ◽

T. Korakianitis ◽

F. Motallebi

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Surface Curvature ◽

Design Approach ◽

Space Applications ◽

Continuous Surface ◽

Low Reynolds ◽

Drag Ratio ◽

Lift To Drag Ratio ◽

High Angles Of Attack

ABSTRACTLow Reynolds number blade profiles of ReC=105–2×105 as based on the chord length and used for small unnamed air vehicles, and near space applications are investigated for single and counter-rotating (co-axial) proprotors, i.e. acting as rotors or propellers. Such profiles are prone for early stall, significantly reducing their maximum lift to drag ratio. Two profiles previously designed by our continuous surface curvature design approach named as CIRCLE are investigated in order to improve the performance of the proprotors. The profiles are redesigns of the common symmetric NACA0012 and asymmetric E387 profiles. Using general arguments based on composite efficiency and rotor’s lift to drag ratio, the performance envelope is noticeably increased when using the redesigned profiles for high angles of attack due to stall delay.A new approach is derived to account for the distance between the rotors of a co-axial proprotor. It is coupled with a blade element method and is verified against experimental results. Single and co-axial CIRCLE-based proprotors are investigated against the corresponding non-CIRCLE-based proprotors at hover and axial translation. Noticeable improvements are observed in thrust increase and power reduction at high angles of attack of the blade’s profiles, particularly for the co-axial configuration. Plots of thrust, torque, power, composite efficiency and aerodynamic efficiency distributions are given and analysed.

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