Characterization of the Aeroacoustic Properties of the SOFIA Cavity and its Passive Control

Sven Schmid (), Marius Kütemeyer (), Thorsten Lutz () and Ewald Krämer ()
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Sven Schmid: NASA Ames Research Center, SOFIA Science Center
Marius Kütemeyer: NASA Ames Research Center, SOFIA Science Center
Thorsten Lutz: Institut für Aerodynamik und Gasdynamik
Ewald Krämer: Institut für Aerodynamik und Gasdynamik

A chapter in High Performance Computing in Science and Engineering, Garching/Munich 2009, 2010, pp 207-218 from Springer

Abstract: Abstract The American and the German Aerospace centers NASA and DLR are working together to build and operate the Stratospheric Observatory For Infrared Astronomy - SOFIA, a 2.5 m reflecting telescope housed in an open cavity on board of a Boeing 747 aircraft. The observatory operates in the stratosphere at an altitude above 13 km to observe astronomical objects in the infrared region of the electromagnetic spectrum. The flow over the open telescope port during the observation presents some challenging aerodynamic and aeroacoustic problems. Pressure fluctuations inside the cavity excite structural vibrations and deteriorate the image stability. NASA successfully optimized the shape of the cavity aperture by means of extensive wind-tunnel studies to mitigate the flow unsteadiness in the cavity. The simulations performed within the present project focus on different aeroacoustic aspects of the SOFIA cavity. Several URANS (Unsteady Reynolds Averaged Navier Stokes) simulations were carried out to study the impact of the cavity door position during opening and closing on the unsteady flow. The impact of the misalignment between the SOFIA telescope assembly and the aperture assembly was investigated with separately conducted Detached Eddy Simulations (DES). Moreover the remaining potential to improve the aeroacoustic characteristics by optimizing the aperture aft ramp geometry and installing a porous fence upstream of the cavity was analyzed with URANS and DES simulations as well.

Keywords: Shear Layer; Sound Pressure Level; Unsteady Pressure; Infrared Astronomy; Porous Fence (search for similar items in EconPapers)
Date: 2010
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Persistent link: https://EconPapers.repec.org/RePEc:spr:sprchp:978-3-642-13872-0_18

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DOI: 10.1007/978-3-642-13872-0_18

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