Flow around a helically twisted elliptic cylinder
Woojin Kim1, Jungil Lee2 and Haecheon Choi1,3,a)
- HIDE AFFILIATIONS
1 Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, South Korea
2 Department of Mechanical Engineering, Ajou University, Suwon 16499, South Korea
3 Institute of Advanced Machines and Design, Seoul National University, Seoul 08826, South Korea
a) Author to whom correspondence should be addressed. Electronic mail: choi@snu.ac.kr
Phys. Fluids 28, 053602 (2016); http://dx.doi.org/10.1063/1.4948247
Abstract
In the present study, we conduct unsteady three-dimensional simulations of flows around a helically twisted elliptic (HTE) cylinder at the Reynolds numbers of 100 and 3900, based on the free-stream velocity and square root of the product of the lengths of its major and minor axes. A parametric study is conducted for Re = 100 by varying the aspect ratio (AR) of the elliptic cross section and the helical spanwise wavelength (λ). Depending on the values of AR and λ, the flow in the wake contains the characteristic wavelengths of λ, 2λ, 6λ, or even longer than 60λ, showing a wide diversity of flows in the wake due to the shape change. The drag on the optimal (i.e., having lowest drag) HTE cylinder (AR = 1.3 and λ = 3.5d) is lower by 18% than that of the circular cylinder, and its lift fluctuations are zero owing to complete suppression of vortex shedding in the wake. This optimal HTE configuration reduces the drag by 23% for Re = 3900 where the wake is turbulent, showing that the HTE cylinder reduces the mean drag and lift fluctuations for both laminar and turbulent flows.
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NOTA DESTE BLOGGER:
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Faltou inspiração da natureza nos engenheiros brasileiros que construíram a ciclovia da Av. Niemeyer no Rio de Janeiro em 21/04/2016.
Mas Darwin não tinha eliminado de vez a questão de design na natureza? Richard Dawkins não pontificou que design é ilusão na natureza? Então por que cargas d'água esses cientistas foram buscar "design" em narcisos amarelos para estruturas estáveis??? NOTA BENE: ESTRUTURAS ESTÁVEIS!
Faltou inspiração da natureza nos engenheiros brasileiros que construíram a ciclovia da Av. Niemeyer no Rio de Janeiro em 21/04/2016.
