Airborne Aero-Optics Laboratory

Jumper, Eric J.; Zenk, Michael A.; Gordeyev, Stanislav; Cavalieri, David; Whiteley, Matthew R.

doi:10.1117/1.oe.52.7.071408

Cited by 57 publications

(22 citation statements)

References 8 publications

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“…where A 1 is the peak field strength, w 1 is the beam radius and R is the phase front curvature in plane z ¼ z 1 where P ¼ ∫ ∫ A 1 ðx;y;z 1 ÞA Ã 1 ðx;y;z 1 Þdxdy ¼ w 2 1 ∕2π½A 1 ðz 1 Þ 2 is proportional to the total power. The derivative of the second term can be calculated, and this part is then found to be an odd function of x that when integrated, reduces to zero.…”

Section: Optical Propagationmentioning

confidence: 99%

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Numerical laser beam propagation using large eddy simulation of a jet engine flow field

et al. 2015

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In certain directed infrared countermeasure (DIRCM) situations, the laser beam path may have to pass close to the engine exhaust plume of the aircraft and models of plume turbulence are needed for DIRCM performance simulations. The jet engine plume was modeled using large eddy simulation (LES), providing time resolved information about the large scale turbulent eddies. The refractive index data from the LES calculations were integrated along the propagation path to produce time resolved phase screens for optical beam propagation. The phase screens were used to calculate laser beam parameters including beam wander and power-in-bucket (PIB). Numerical beam propagation resulted in a root-mean-square beam wander of 200 μrad for the small turbojet engine studied. The PIB was calculated for beams with 80 μrad and 2 mrad divergence having equal beam diameter when passing through the plume. For the beam with low divergence, the average PIB was reduced from 0.23 to 0.040, while the beam with wider divergence showed no significant reduction. In both cases, the plume introduced significant temporal variation of the instantaneous PIB. The beam wander is not affected by the divergence, but only depends on beam size. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/17/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 085101-2 August 2015 • Vol. 54(8) Henriksson et al.: Numerical laser beam propagation using large eddy simulation of a jet engine flow field Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/17/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 085101-9 August 2015 • Vol. 54(8) Henriksson et al.: Numerical laser beam propagation using large eddy simulation of a jet engine flow field Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/17/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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Section: Optical Propagationmentioning

confidence: 99%

“…1 Even more severe turbulence effects occur when the hot engine exhaust gases are mixed with the ambient air. Applications include sensing, targeting, communications, and self-protection.…”

Section: Introductionmentioning

confidence: 99%

Numerical laser beam propagation using large eddy simulation of a jet engine flow field

et al. 2015

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“…Normalized aero-optical aberrations tend to collapse onto a curve that is a function of two quantities: a lookback angle, α, and a modified elevation angle, β. These two quantities can be expressed 8…”

Section: Introductionmentioning

confidence: 99%

“…Picture of the Airborne Aero-Optics Laboratory (AAOL). The pointing aircraft is depicted on the left and the tracking aircraft on the right 8. …”

mentioning

confidence: 99%

A Robust Modification of a Predictive Adaptive-Optic Control Method for Aero-Optics

Burns

Jumper

Gordeyev

2016

47th AIAA Plasmadynamics and Lasers Conference

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A modification of a previous predictive adaptive-optic controller is presented in this paper. Conventional adaptive-optic controllers suffer from bandwidth limitations caused by latency in their control loops. This latency severely limits their capabilities in aero-optic applications that cannot be overcome with conventional feedback techniques. Our method uses prior knowledge of flow behavior to predict future behavior, and thus overcome deadtime. We have modified our previous neural network controller to use a linearized predictor, which we demonstrate to be more accurate, more robust to noise and flow disturbances, and less computationally expensive. Our previous neural network method showed disturbance rejection in the range of 35-55% in simulation over our test conditions in the most optically-active regions, while the improved method shows disturbance rejection between 45-75% over the same range. Additionally, we demonstrate that the predictive control method is stable, even in the presence of latency uncertainty.

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“…The tested hemisphere-on-cylinder turret model, with a diameter, D, of 30.5 cm and a cylindrical base height of H = 11.1 cm, was an exact replica of AAOL turret shell, shown in Figure 2 used for aero-optical flight tests [16]. The turret has a rotating portion, or a "donut", allowing to continuously change the elevation angle of the window and the whole turret assemble can be rotated to any azimuthal angle.…”

Section: Methodsmentioning

confidence: 99%

The Comparison of Unsteady Pressure Field over Flat- and Conformal-Window Turrets using Pressure Sensitive Paint

Gordeyev

Lucca

Jumper

et al. 2013

44th AIAA Plasmadynamics and Lasers Conference

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Spatially-temporally-resolved unsteady pressure fields on a surface of a hemisphere-oncylinder turret with either a flat-or a conformal-window were characterized using fastresponse pressure sensitive paint at M = 0.33 for several window viewing angles. Various statistical properties of pressure fields were computed and geometry effects on unsteady pressure, including an effect of either flat-or conformal-window, were analyzed and discussed. Proper orthogonal decomposition were also used to extract dominant pressure modes and corresponding temporal coefficients and to analyze and compare instantaneous pressure structures for different turret geometries and viewing angles. In addition, the effects of gaps and 'smile' cut-outs present on the turret were investigated.

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Airborne Aero-Optics Laboratory

Cited by 57 publications

References 8 publications

Numerical laser beam propagation using large eddy simulation of a jet engine flow field

Numerical laser beam propagation using large eddy simulation of a jet engine flow field

A Robust Modification of a Predictive Adaptive-Optic Control Method for Aero-Optics

The Comparison of Unsteady Pressure Field over Flat- and Conformal-Window Turrets using Pressure Sensitive Paint

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