Bio-mimicry inspired tall buildings: The response of cactus-like buildings to wind action at Reynolds Number of 104

Letchford, Chris; Lander, Daniel; Case, Peter; Dyson, Anna; Amitay, Michael

doi:10.1016/j.jweia.2016.01.001

Cited by 15 publications

(16 citation statements)

References 21 publications

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“…The presence of these vortices was also demonstrated experimentally (Wang et al, 2014) and numerically (Jie and Liu, 2016) at a higher Reynolds number of 54,000. Letchford et al (2016) on cactus-shaped cylinders placed in smooth and rough boundary layers at Reynolds numbers from 10,000 to 20,000 showed the reduction of the aerodynamic coefficients and an increase in the Strouhal number, which is consistent with the two-dimensional results by Talley et al (2001). This indicates that the results from previous studies for the two-dimensional case also translate to three-dimensional structures.…”

Section: Introductionsupporting

confidence: 89%

“…Unlike in previous studies on cactus-shaped cylinders with many ribs (Talley et al, 2001;Oki, 2004, 2005;Letchford et al, 2016) For the three-rib case the C d value at α max is close to the value for the smooth cylinder case. In contrast, a substantial reduction in C d compared to the smooth cylinder case is observed for the four-rib case at α > 39 • (α/α max > 0.86).…”

Section: Drag Coefficientsupporting

confidence: 41%

“…in the three-rib case. For cactus configurations with many ribs reduction in the unsteady drag forces was found by Talley et al (2001), Letchford et al (2016) for the same Reynolds number and by Babu and Mahesh (2008) for the laminar regime. In the current study, a significant reduction is observed only for the four-rib configuration at high angles of attack.…”

Section: Drag Coefficientmentioning

confidence: 51%

“…The Reynolds number of the flow, based on free-stream velocity U ∞ and outer diameter D was set at 20,000. This, biologically relevant, Reynolds num- ber has already been used in a number of studies related to the Saguaro cactus (Talley et al, 2001;Talley and Mungal, 2002;Letchford et al, 2016). A nondimensional time step of ∆tU ∞ /D = 7.833 × 10 −3 was used for the numerical simulations.…”

Section: Methodsmentioning

confidence: 99%

“…Most previous studies on flow past cactus-shaped cylinders with many ribs did not report on angle of attack dependence (Talley et al, 2001;Oki, 2004, 2005;Liu et al, 2011;Wang et al, 2014;Jie and Liu, 2016) or stated that the influence of the angular position is insignificant (Letchford et al, 2016). Oweis et al (2011Oweis et al ( , 2013, who studied the flow around a cactus-shaped cylinder with eight ribs, pointed out that a change in the angular position will have an effect on the flow characteristics.…”

Section: Lift Coefficientmentioning

confidence: 99%

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Angle of attack dependence of flow past cactus-inspired cylinders with a low number of ribs

Zhdanov

Busse

2019

European Journal of Mechanics - B/Fluids

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The aerodynamic coefficients and the Strouhal number of cylinders with three and four ribs, inspired by succulents Euphorbia trigona and Euphorbia Abyssinica are investigated using 2D Unsteady Reynolds-Averaged Navier-Stokes simulations at Reynolds number 20,000. Both configurations show a significant dependence of the studied characteristics on the angle of attack. The obtained results are compared to the smooth circular cylinder, previous results for cylinders with 24 ribs based on the Saguaro cactus, and cylinders with triangular and square cross-sections. Relative to the circular cylinder, the mean drag coefficient is lowered only for the four-rib case at high angles of attack. However, at some angular positions, the ability to reduce unsteady force fluctuations exceeds Saguaro-inspired cylinders. For both shapes studied, the Strouhal number at most angles of attack is lower compared to both the circular cylinder and cylinders with 24 ribs at the same Reynolds number. The minimum values of the aerodynamic coefficients for both configurations are related to the angular orientation. For the four-rib case a critical angle of α cr ≈ 40 • is observed, at which the mean drag coefficient and the fluctuating lift coefficient attain their minima. The mean lift coefficient reaches at this angle its maximum value before a sudden drop for higher angles of attack. Therefore, for cactus-shaped cylinders with four ribs high angles of attack give the optimum orientation relative to prevailing winds.

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Section: Introductionsupporting

confidence: 89%

Section: Drag Coefficientsupporting

confidence: 41%