Experiments in Line Vibration and Associated Drag for Kites

Dunker, Storm; Meile, Walter; Brenn, Günter

doi:10.2514/6.2015-2154

Cited by 3 publications

(4 citation statements)

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“…This may contribute to a stronger resistance to VIV and could be a reason why it resulted in the highest St value of the tested kite lines. This corresponds to the findings of Dunker et al [25].…”

Section: Discussionsupporting

confidence: 93%

“…The flow-induced sound of the HMPE core kite lines with braided sheath and helical surface protrusions (see Table 2) developed by Dunker et al [25] was measured and compared to the sound spectra of a reference line with similar construction and smooth surface (Ref 3). Figure 8 shows the A-leveled sound pressure level of these lines over a frequency of 100 Hz to 10 000 Hz at different wind speeds and various angles of attack.…”

Section: Influence Of Helical Surface Protrusions On Flowinduced Kite...mentioning

confidence: 99%

“…Flexible, tensioned kite lines in cross-flow are susceptible to vibrations with the vortex shedding frequency. First investigations of the influence of helical surface protrusions on the aerodynamic behaviour on long flexible structures like kite lines have been conducted by Dunker et al [25]. Kite lines with helical surface protrusions were developed to reduce vortex-induced line vibrations with the objective to lower drag.…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of flow-induced sound of kite lines

Saur,

Riedel,

Dunker

et al. 2023

Acta Acust.

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In times of increasing importance of renewable energies, airborne wind energy (AWE) systems represent an emerging extension to conventional wind turbines. Many AWE systems use powerful kites to provide tether traction to mechanically unwind the tether, generating electricity on the ground. In addition to the traction tether, a large number of kite lines spanning the kite are moved through the air at high speed. This can produce a loud unpleasant whistling noise on the ground, which is due to a superposition of the aeolian tones of the many different lines. In the present work, differently structured kite lines were investigated in the aeroacoustic wind tunnel with respect to their sound radiation when they were exposed to a flow at up to 34 ms−1 resulting in Re ≦ 7300 and angles of attack (AOA) in the range of 90° ≧ AOA ≧ 45°. It was found that greater surface roughness increases sound radiation while line tension has negligible influence. By weaving a single-helix-shaped protrusion into the sheath of the kite line, the total radiated sound pressure level can be reduced by up to 9 dB. If the line itself has a helical contour, even a reduction of up to 11.5 dB is reachable. For decreasing AOA the noise suppression effect of helical surface protrusions and helical line shape is significantly reduced. The results provide initial guidelines on how to effectively reduce sound radiation from aircraft kites. Further investigations should consider the individual contributions of fluid and structural sounds to the total radiated sound of a flying kite.

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Section: Discussionsupporting

confidence: 93%

Section: Influence Of Helical Surface Protrusions On Flowinduced Kite...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of flow-induced sound of kite lines

Saur,

Riedel,

Dunker

et al. 2023

Acta Acust.

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“…With a variable apparent wind velocity, additional complexity is added to the optimization, which caused convergence issues in the FSI routine. Therefore, we decided to fix the apparent wind speed to 40 m/s, which is obtained with a wind speed of 10 m/s and a glide ratio of 6, often found for ram‐air kites . The fixed apparent wind speed can be seen as a design apparent wind speed.…”

Section: Analysis Of Ram‐air Kitesmentioning

confidence: 99%

Ram‐air kite airfoil and reinforcements optimization for airborne wind energy applications

2019

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We present a multidisciplinary design optimization method for the profile and structural reinforcement layout of a ram‐air kite rib. The aim is to minimize the structural elastic energy and to maximize the traction power of a ram‐air kite used for airborne wind energy generation. Because of the large deformations occurring during flight, a fluid‐structure interaction (FSI) routine is included in the optimization, which determines the actual deformed rib geometry and its corresponding aerodynamic characteristics. A qualitative comparison between FSI inclusion and exclusion in the optimization is given. Discrepancies in airfoil profile and structural layout are observed.

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Tether and Bridle Line Drag in Airborne Wind Energy Applications

Dunker¹

2018

Airborne Wind Energy

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Experiments in Line Vibration and Associated Drag for Kites

Cited by 3 publications

References 1 publication

Experimental investigation of flow-induced sound of kite lines

Experimental investigation of flow-induced sound of kite lines

Ram‐air kite airfoil and reinforcements optimization for airborne wind energy applications

Tether and Bridle Line Drag in Airborne Wind Energy Applications

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