| Autor: |
Stanislav Gordeyev, Eric J. Jumper, Nicholas DeLucca, Donald J. Wittich, Kirtland Afb |
| Rok vydání: |
2013 |
| Předmět: |
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| Zdroj: |
51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. |
| Popis: |
Aero-optical effects around the hemispheric turret at forward looking angles for azimuthal angles of 0°, 45° and 85° at the elevation angle of 45° were parametrically investigated for multiple turret geometries and flow conditions. 2D wavefronts were acquired with a 32x32 sub-aperture resolution at 25 kHz with global beam jitter and accelerometer measurements acquired simultaneously at 100 kHz. Turret geometry was varied between flat and conformal window and from full hemisphere-on-cylinder to hemisphere-only and a partially-protruding hemisphere. Incoming boundary layer was varied between δ/D = 3% and δ/D = 15% while freestream Mach number was 0.3-0.6. Time-averaged OPDRMS was computed for each case along with dominant POD modes, corresponding energy content and the global jitter spectra. A slow, unsteady defocus operating at normalized frequency of ST < 0.1 was found to be the primary component of wavefront aberration for these angles. The strength and exact shape of the defocus was shown to depend on not only the turret geometry, but also the incoming boundary layer thickness. The boundary layer thickness was shown to more substantially affect the hemisphere-only and partially-protruding hemisphere turrets than the full turret, introducing an additional broad-band global tip/tilt component between ST = 0.4 to ST = 3. The unsteady defocus and tip/tilt introduced were hypothesized to be related to the necklace vortex and wake instabilities driving slow changes in the global pressure field. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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