Drag characteristics of ribbons

Auman, Lamar; Dahlke, C. W.

doi:10.2514/6.2001-2011

Cited by 8 publications

(8 citation statements)

References 1 publication

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“…However, despite this, the data at the highest aspect ratios and areas actually has closer agreement to the power-law approximation. It must also be pointed out that the data gathered by Auman et al [1,3,4] used loops and streamers that are significantly longer than those considered here. These other loops exhibited streamerlike characteristics because testing was conducted at the higher velocity range of 27 m=s < U < 46 m=s.…”

Section: Variation Of the Drag Coefficient With Aspect Ratiomentioning

confidence: 93%

“…This means that longer loops, which would suffer only large-amplitude oscillations over a smaller fraction of their length, will transmit less disturbance towards the luff, and hence the payload. This fact was first demonstrated by Auman and Dahlke [3]. Empirical formulas for streamers and loops have been determined to describe the variation of the drag coefficient with the aspect ratio [4]: The drag characteristics have been measured for nylon loops (material properties not specified) and remain valid over two velocity ranges, 27 m=s < U < 46 m=s and a higher range of 280 m=s < U < 600 m=s.…”

Section: Introductionmentioning

confidence: 98%

“…The effects of cloth properties on the drag and flutter characteristics of loops are certainly an area for further research. Therefore, the study conducted here attempts to incorporate the effects of material properties by testing pure cotton of relatively similar material thickness, rather than the nylon cloth previously considered [1,3,4].…”

Section: Introductionmentioning

confidence: 99%

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Drag and Flutter Characteristics of Loop Membranes

Carruthers

Filippone²

2007

Journal of Aircraft

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We present the results of experimental investigations on the aerodynamic characteristics of high-drag devices with flexible membranes joined at their short ends (loops). The loops were placed in a low-speed wind tunnel and tested at speeds up to 19 m=s. The range of Reynolds numbers was Re 2 10 5 -2 10 6 . The loops were tested for a variety of aspect ratios, from 3.3 to 30, three planform areas, and two mounting methods. Results are presented for the drag coefficient and for the flutter characteristics. We prove that with a low aspect ratio the loops form a teardrop shape and their flutter mode is a sinusoidal-like oscillation. Furthermore, the drag coefficient decreases with the increasing wind speed, but it depends strongly on the aspect ratio and the planform area. Empirical correlations for the drag coefficient are polynomial equations. Nomenclature A = planform area, m 2 C D = drag coefficient based on the planform area (single side area) c 1 , c 2 = coefficients in Eq. (1) Re = Reynolds number based on loop length U = freestream velocity, m=s = loop thickness, mm

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Section: Variation Of the Drag Coefficient With Aspect Ratiomentioning

confidence: 93%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Drag and Flutter Characteristics of Loop Membranes

Carruthers

Filippone²

2007

Journal of Aircraft

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“…While this phenomenon has been demonstrated for laminar flows with in-plane tension provided by gravity (Taneda, 1968), its observation in turbulent flows of more practical interest has suffered because of geometric irregularities of the sheet up to the point of instability (see Fairthorne, 1930;Auman and Dahlke, 2001;Carruthers and Filippone, 2005). Like a flat plate, the drag coefficient of a flexible sheet decreases with increasing aspect ratio (Taneda, 1968;Auman and Dahlke, 2001;Carruthers and Filippone, 2005); and, furthermore, we can expect its magnitude to approach that of a flat plate under sufficiently small elastic deformations. To the authors' knowledge, the effect of additional rigidity through in-plane tension, although likely to postpone an expected rise in the drag coefficient at the onset of a fluid-elastic instability, has hitherto not been studied.…”

Section: Introductionmentioning

confidence: 99%

Experiments on the stability and drag of a flexible sheet under in-plane tension in uniform flow

Morris-Thomas

Steen

2009

Journal of Fluids and Structures

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A flexible sheet in uniform parallel flow is studied in order to quantify its fluid dynamic drag and fluid-elastic stability characteristics. An experimental campaign is undertaken that involves a cantilevered sheet in air flow characterised by Reynolds numbers of order R ¼ 10 4 210 6 . The properties of the sheet include: constant mass per unit area; small but finite flexural rigidity; varying aspect ratios from within the range 0:43ol=Lo1, where L and l denote the length and width, respectively; and tension applied at the trailing edge. The unique aspect of the present work is an investigation into the influence of in-plane tension on both the fluid drag and fluid-elastic stability of the sheet. In the absence of tension, the configuration resembles a flag and the drag coefficient is observed to decrease with increasing aspect ratio and Reynolds number. In the presence of tension, the fluid drag is significantly reduced in the region below the critical flow velocity at which convected wave instabilities appear. This critical flow velocity can be increased through the moderate application of in-plane tension. Under lateral tension, the drag of the sheet is given to good approximation by the turbulent boundary layer drag law for a flat plate. Once stability is lost, however, the drag coefficient increases rapidly with Reynolds number due to convected waves travelling over the sheet's surface. r

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“…Here, flow separation at the trailing edge is of little consequence compared to boundary layer induced tension and fluid added mass effects. Such a characterisation would encompass the performance of long slender bodies of more general cross-section [6] and in particular ribbons and streamers [7,8,9,10].…”

Section: Introductionmentioning

confidence: 99%

The Response of a Flexible Sheet Under Axial Tension Immersed in Parallel Flow

Morris-Thomas

Steen

2008

Volume 4: Ocean Engineering; Offshore Renewable Energy

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This paper explores the fluid-elastic response of a cantilevered flexible sheet in the presence of uniform airflow. The leading edge of the sheet is clamped, while at the trailing edge, in-plane tension is applied to provide additional rigidity to the sheet's small but finite bending stiffness. We outline a series of experiments performed in a wind tunnel with the purpose of examining fluid-elastic instabilities. In particular, we examine the role of in-plane tension induced rigidity and how it influences static divergence and convected wave instabilities. The flow is characterised by Reynolds numbers of order 10 5 -10 6 and we specifically examine a sheet with an aspect ratio of L/l = 1.33. A unique aspect of this present work, is the direct measurement of the sheet's three-dimensional displacement through an optical tracking method with a grid of passive markers placed on the sheet surface. We show the evolution of the sheet surface from stability, through to divergence, and then finally into flutter. The frequency composition of the flutter event shows higher harmonic components that suggest significant nonlinearities. Tension induced rigidity plays a crucial role in the response of the sheet to the fluid in both postponing and suppressing instabilities. arXiv:1101.2464v1 [physics.flu-dyn]

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Drag characteristics of ribbons

Cited by 8 publications

References 1 publication

Drag and Flutter Characteristics of Loop Membranes

Drag and Flutter Characteristics of Loop Membranes

Experiments on the stability and drag of a flexible sheet under in-plane tension in uniform flow

The Response of a Flexible Sheet Under Axial Tension Immersed in Parallel Flow

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