Characterization of a Forced Two-Dimensional, Weakly-Compressible Shear Layer.

Rennie, R. Mark; Duffin, Daniel A.; Jumper, Eric J.

doi:10.2514/6.2007-4007

Cited by 11 publications

(27 citation statements)

References 16 publications

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“…The CSLWT mixes co-directional high-and low-speed flows at high subsonic flow speeds (up to Mach 1.0) to create a shear layer that is aero-optically active, and representative of the kinds of aero-optic flows likely to be encountered on flight vehicles. Details on the design and flow characteristics of the CSLWT can be found in [5,10].…”

Section: B Experimentsmentioning

confidence: 99%

“…In this case, computation of the conjugate waveform is predicated on an accurate determination of the original aero-optic aberration. Even for feed-forward AO correction schemes, in which flowcontrol techniques are used to improve the frequency bandwidth of the aberrating flow, it is still anticipated that low-order optical measurements will still be used to synchronize the AO scheme with the controlled flow aberrations [5].…”

Section: Introductionmentioning

confidence: 99%

“…4 Research Specialist, Department of Aerospace and Mechanical Engineering, Senior Member AIAA. 5 Professor, Department of Aerospace and Mechanical Engineering, Fellow AIAA.…”

mentioning

confidence: 99%

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Measurement of Beacon Anisoplanatism Through a Two-Dimensional Weakly-Compressible Shear Layer

Rennie

Whiteley

Cross

et al. 2008

39th Plasmadynamics and Lasers Conference

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An experimental investigation was conducted into the effectiveness with which aero-optic aberrations imposed on a collimated reference beam could be evaluated using a point-source beacon. The experiments were conducted in the University of Notre Dame's Compressible Shear-Layer Wind Tunnel which was used to create an optically-active shear-layer flow with high-speed Mach number of 0.8. Anisoplanatic effects included a difference in wavefront shape between the (spherical wavefront) beacon and the (planar wavefront) reference beam, and a difference in the regions of the flow sampled by the beacon and reference beams. A modal compensation approach was used to minimize the anisoplanatism between the beacon and reference wavefronts, which showed that the best compensation results were obtained when the shear layer was regularized using mechanical forcing.

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Section: B Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Measurement of Beacon Anisoplanatism Through a Two-Dimensional Weakly-Compressible Shear Layer

Rennie

Whiteley

Cross

et al. 2008

39th Plasmadynamics and Lasers Conference

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“…2 dx\ { A P-A P /2 (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) where A and B arc coefficients defining the tilt and piston being removed. Z-tilt is defined as a linear fit to the wavefront and corresponds to values of A and B that minimize Eq.…”

Section: Opd Rnn (Apj) = \-J [Opd(xt)-{a(t) + Xb(t))]mentioning

confidence: 99%

“…[17,21] Simulations using the WCM indicate the existence of clear, regular structures and greatly regularized optical distortions associated with those structures. Figure 27 shows a reconstructed wavefront from optical experimental data taken through a M = 0.78 shear layer being forced at the trailing edge of the splitter plate.…”

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confidence: 99%

Toward Adaptive Optic Mitigation of Aero-Optic Effects

Jumper¹

2009

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instrut maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate c suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be £ information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRL (From -To) When a laser beam propagates through a variable-index-of-refraction, turbulent fluid, its wavefront becomes aberrated, reducing associated optical-system performance. For flight Mach numbers as low as 0.3 Mach, turbulence in the flow past the aircraft become important in aberrating wavefronts (aero-optics). This report briefly reviews the mechanisms responsible for these aberrations in free-shear-layer flows. The report begins with describing an historic demonstration performed under this effort that combined the use of flow control and feed-forward adaptive optics to correct the aberrations imposed on an otherwise collimated laser beam projected through a heated jet and a Mach 0.8 free shear layer, respectively; this historic demonstration included a man in the loop. The report then describes the development of an automated control system that removes the man in the loop. Also described is some additional work performed under this grant that examined a spatial-filter approach to analyzing the effect of apertures on several aspects of laserbeam control. REPORT DATE (DD-MM-YYYY) 15-02-2009 REPORT TYPE FINAL REPORT DATES COVERED15 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services. Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204. Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENT UL SUPPLEMENTARY NOTES14. ABSTRACT This report describes aero-optic research at the University of Notre Dame. When a laser beam propagates through a variable-index-of-refraction, turbul...

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