A Low-Dimensional Model of Shock-Wake Interaction Over Turrets at Transonic Speeds

53rd AIAA Aerospace Sciences Meeting

2015

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Point pressure measurements were performed on a hemisphere-on-cylinder turret in-flight and in the wind tunnel at the University of Notre Dame. Measurements were performed at a total of 36 different locations on the turret. The pressure coefficients (c p) was analyzed versus viewing angle for each Mach number and were compared with previous experiments and theoretical values based on the potential flow. At transonic Mach numbers, the dominant frequencies of the motion of the local shock over the turret were investigated. The turret wake was also investigated and it was shown that the "smiles" cutouts and the local shock can have a "regularizing" effect of decreasing higher frequency fluctuations while increasing low frequency fluctuations. Unsteady forces acting on the turret were computed from the pressure fields and their dependence on the Mach number and turret geometry was discussed.

Section: Discussionsupporting

confidence: 59%

Section: Shock Effect Analysissupporting

confidence: 67%

Global Unsteady Pressure Fields Over Turrets In-Flight

Lucca

Gordeyev

53rd AIAA Aerospace Sciences Meeting

2015

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“…The shock location was captured in α-β coordinates for given fixed β. The discontinuity of a shock causes a sharp change in the wavefront, so shock tracking was done by stepping along α at the β of interest to find the location of maximum slope in the OPD RMS ; a similar analysis was performed to study the shock dynamics on a 2D turret in the wind tunnel in [4,5]. The black filled circles show the location of maximum positive wavefront slope, which is presumed to be related to the instantaneous shock position.…”

Section: Methodsmentioning

confidence: 99%

“…The most notable difference from a turret in subsonic flow is the presence of a local shock on the turret. The exact location and behavior of this shock is dependent on the freestream Mach number [5,8,9]. This shock also can induce separation downstream of it, either causing premature wake formation or locally introducing additional optically-aberrating turbulence.…”

Section: Aero-optical Investigation Of Transonic Flow Features Amentioning

confidence: 99%

“…Because AAOL-T is a continuation of AAOL many of the original objectives of the AAOL program are also part of the objectives of the present AAOL-T program. The AAOL-T program continues to include Aero-Optics as its primary focus but now at higher Mach numbers [5]; however, the new program has additional objectives that were not part of AAOL: these specifically include aero-mechanical studies, more emphasis on mitigation approaches that include adaptive optics, and specific emphasis on support of other programs. In the year-one annual report, we reported on approaches in understanding unsteady pressure data collected on the Cessna Citation version of the AAOL continued from the end of the AAOL program into the AAOL-T program.…”

Section: Introductionmentioning

confidence: 99%

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Airborne Aero-Optics Laboratory - Transonic (AAOL-T)

53rd AIAA Aerospace Sciences Meeting

2015

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Physics and Measurement of Aero-Optical Effects: Past and Present

Gordeyev

2017

Annu. Rev. Fluid Mech.

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122

The field of aero-optics is devoted to the study of the effects of turbulent flow fields on laser beams projected from airborne laser systems. This article reviews the early and present periods of research in aero-optics. Both periods generated impressive amounts of research activity; however, the types and amount of data differ greatly in accuracy, quality, and type owing to the development of new types of instrumentation available to collect and analyze the aberrated wave fronts of otherwise collimated laser beams projected through turbulent compressible flow fields of the type that form over beam directors. This review traces the activities and developments associated with both periods but particularly focuses on the development of modern high-bandwidth wave-front sensors used in the present research period. We describe how these modern wave-front data are collected and analyzed and the fluid mechanic information that can be gleaned from them; the use of these data in the fundamental study of turbulence is emphasized.