Hydrodynamic behavior of two-dimensional tandem-arranged flapping flexible foils in uniform flow

2020 ◽  
Vol 32 (2) ◽  
pp. 021903
Author(s):  
Liang Cheng
Keyword(s):  
Uniform Flow ◽  
Two Dimensional ◽  
Hydrodynamic Behavior ◽  
Flexible Foils

A Comparison of Correction Methods Used in the Evaluation of Drag Coefficient Measurements for Two-Dimensional Rectangular Cylinders

1979 ◽  
Vol 101 (4) ◽  
pp. 506-510 ◽  
Author(s):  
J. Courchesne ◽  
A. Laneville
Keyword(s):  
Drag Coefficient ◽  
Experimental Evaluation ◽  
Uniform Flow ◽  
Two Dimensional ◽  
Rectangular Cylinders

This paper describes an experimental evaluation of available drag correction formulae and theories for blockage effects applicable to two-dimensional rectangular cylinders immersed in a low-turbulence uniform flow. It is observed that empirical formulae are functions of the afterbody length and that Maskell’s theory has the tendency to overestimate the correction.

A paradox of hovering insects in two-dimensional space

2008 ◽  
Vol 617 ◽  
pp. 207-229 ◽  
Author(s):  
MAKOTO IIMA
Keyword(s):  
External Force ◽  
Stokes Equations ◽  
Hydrodynamic Force ◽  
Dimensional Space ◽  
Exact Formula ◽  
Uniform Flow ◽  
Far Field ◽  
Two Dimensional ◽  
Field Representation ◽  
Whole Space

A paradox concerning the flight of insects in two-dimensional space is identified: insects maintaining their bodies in a particular position (hovering) cannot, on average, generate hydrodynamic force if the induced flow is temporally periodic and converges to rest at infinity. This paradox is derived by using the far-field representation of periodic flow and the generalized Blasius formula, an exact formula for a force that acts on a moving body, based on the incompressible Navier–Stokes equations. Using this formula, the time-averaged force can be calculated solely in terms of the time-averaged far-field flow. A straightforward calculation represents the averaged force acting on an insect under a uniform flow, −〈V〉, determined by the balance between the hydrodynamic force and an external force such as gravity. The averaged force converges to zero in the limit 〈V〉 → 0, which implies that insects in two-dimensional space cannot hover under any finite external force if the direction of the uniform flow has a component parallel to the external force. This paradox provides insight into the effect of the singular behaviour of the flow around hovering insects: the far-field wake covers the whole space. On the basis of these assumptions, the relationship between this paradox and real insects that actually achieve hovering is discussed.

The Choice of a Hodograph Boundary for Contracting Ducts

1964 ◽  
Vol 68 (642) ◽  
pp. 420-422 ◽  
Author(s):  
J. C. Gibbincs
Keyword(s):  
Flow Pattern ◽  
Incompressible Flow ◽  
Uniform Flow ◽  
Infinite Strip ◽  
Two Dimensional ◽  
Contraction Ratio ◽  
Flow Through

A recent paper on the potential incompressible flow through two-dimensional contracting ducts raises some interesting points that are relevant to the hodograph technique for solving this problem.In this paper, Lau obtains a contraction shape by placing a source in a uniform flow that is contained in a doubly infinite strip. The resulting flow pattern is sketched in Fig. 1. The flow is from a region of unit velocity to one of velocity R, where R is the contraction ratio. A streamline, intermediate in position between ψ = 0 and ψ=1.0, is adopted as the contraction profile.

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