Acoustic and aerodynamic design and characterization of a small-scale aeroacoustic wind tunnel

Sarradj, Ennes; Fritzsche, Christoph; Geyer, Thomas; Giesler, Jens

doi:10.1016/j.apacoust.2009.02.009

Cited by 119 publications

(47 citation statements)

References 11 publications

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“…The cabin has a width of 1.55 m, a height of 1.5 m and a length (in streamwise direction) of 2 m. Figure 4 shows a schematic of the experimental setup. Additional information on the aeroacoustic wind tunnel are given by Sarradj et al 32 The dimensions of the wings (Table 1) are not negligible compared to the jet width, which leads to the effect of a partial blockage of the wind tunnel, especially at higher angles of attack. This blockage, which has an impact on the aerodynamic loading of the wings positioned in front of the nozzle, as well as the fact that the flow field around the wings changes in the spanwise and the chordwise direction due to the expanding jet width, are effects that usually require a correction of the angle of attack.…”

Section: Iib Wind Tunnelmentioning

confidence: 99%

Silent Owl Flight: Acoustic Wind Tunnel Measurements on Prepared Wings

Geyer

Sarradj

Fritzsche

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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The wings and feathers of most genera of owls show unique properties that are held responsible for the silent flight of the owls. This ability to fly silently has long been of interest for engineers, with the aim to transfer the basic noise reducing mechanisms to technical applications such as blades of fans and propellers. The present paper describes acoustic and aerodynamic wind tunnel measurements on prepared bird wings of different species, among them two silently flying species of owls, the barn owl (Tyto alba) and the tawny owl (Strix aluco). The different wings are characterized in the study as technical airfoils in terms of their acoustic and aerodynamic performance. The experiments took place in an aeroacoustic open jet wind tunnel using microphone array measurement technique and deconvolution beamforming algorithms. Simultaneously to the acoustic measurements, the lift and drag forces of the wings were captured using a six-component-balance. This study, which is a complementary study to the approach of performing flyover measurements on flying birds, further confirms experimentally that the silent owl flight is a consequence of the special wing and plumage adaptations of the owls and not a consequence of their lower flight speed only.

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Section: Iib Wind Tunnelmentioning

confidence: 99%

Silent Owl Flight: Acoustic Wind Tunnel Measurements on Prepared Wings

Geyer

Sarradj

Fritzsche

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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“…This study included measurements of the flap motion, acoustic measurements and constant temperature anemometry measurements, which were conducted in the small aeroacoustic wind tunnel at BTU Cottbus -Senftenberg [18]. To obtain additional information on the flow structures in the wake of the cylinder, smoke flow visualization measurements were performed in the wind tunnel at TU Bergakademie Freiberg.…”

Section: Methodsmentioning

confidence: 99%

Vortex shedding noise of a cylinder with hairy flaps

Kamps

Geyer

Sarradj

et al. 2017

Journal of Sound and Vibration

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThis study describes the modification of acoustic noise emitted from cylinders in a stationary subsonic flow for a cylinder equipped with flexible hairy flaps at the aft part as a passive way to manipulate the flow and acoustics. The study was motivated by the results from previous water tunnel measurements, which demonstrated that hairy flaps can modify the shedding cycle behind the cylinder and can reduce the wake deficit. In the present study, wind tunnel experiments were conducted on such a modified cylinder and the results were compared to the reference case of a plain cylinder. The acoustic spectrum was measured using two microphones while simultaneously recording the flap motion. To further examine the flow structures in the downstream vicinity of the cylinder, constant temperature anemometry measurements as well as flow visualizations were also performed. The results show that, above a certain Reynolds number, the hairy flaps lead to a jump in the vortex shedding frequency. This phenomenon is similarly observed in the water flow experiments as a jump in the non-dimensional Strouhal number that is related to the change of the shedding cycle. This jump appears to be coupled to a resonant excitation of the flaps and a considerable increase of the flapping amplitude. The specific Reynolds number at which the jump Email addresses: Laura.Kamps@imfd.tu-freiberg.de (Laura Kamps), Thomas.Geyer@b-tu.de (Thomas F. Geyer) Preprint submitted to Journal of Sound and Vibration October 11, 2016 occurs is higher in the present case, which is attributed to the lower added mass in air as compared with the one in water. The flow visualizations confirmed that such action of the flaps lead to a more slender elongated shape of the time-averaged separation bubble. In addition, the hairy flaps induce a noticeable reduction of the tonal noise as well as broadband noise as long as the flaps do not touch each other.

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“…The key performance targets of the DAPR rig are to produce low noise and low turbulence free jet, which are achieved by two large silencers, extensive woven wire mesh screens throughout the circuit and a carefully-designed nozzle. More recently, the Brandenburg Technical University Cottbus in Germany commissioned a new low noise wind tunnel 10 and it is suitable to be used in both the reverberant and anechoic environments. Circular and rectangular nozzles of different contraction ratios can be interchanged, which produce approximately 0.2% and 0.1% freestream turbulence intensities, respectively.…”

Section: Introductionmentioning

confidence: 99%