Shock waves will form by turning supersonic or locally flow and result in an increase the freestream density downstream of shock. This leads to optical distortions that limit effectiveness aircraft-mounted laser systems. In this paper, analytic expressions are developed describe these terms optical-path difference (OPD). Pupil-plane disturbances imposed shock studied for two cases: when is parallel propagation direction on angle relative direction. Upon from pupil plane, analysis shows...

This paper serves as part I of a two-part tutorial on "aero-optical effects." We first present background information to assist with our introduction the topic. Next, we use aerodynamic environment associated hemisphere-on-cylinder beam director decompose resulting aberrations (that arise due aero-optical effects) in terms piston, tilt, and higher-order phase errors. also discuss performance implications that these errors have airborne-laser systems. Recognizing complexity environments, then...

Wind-tunnel experiments were conducted to measure the unsteady surface pressure field on and around a hemisphere-on-cylinder turret of varying protrusion in subsonic flow. These measurements obtained using fast-response pressure-sensitive paint coupled with transducers. The data resulting from Mach 0.5 flow ([Formula: see text]) over partially submerged hemisphere, hemisphere cylinder analyzed proper orthogonal decomposition modal analysis, as well variant this approach referred joint...

We present an analytical study of magnetic damping. In particular, we investigate the dynamics a cylindrical neodymium magnet as it moves through conducting tube. Owing to very high degree uniformity magnetization for magnets, are able provide completely results electromotive force generated in pipe and consequent retarding force. Our expressions shown have excellent agreement with experimental observations.

The work presented here experimentally measures the tilt imposed on a laser beam by atmosphere from Shack-Hartmann wavefront sensor measurements collected in-flight. Tip/tilt is propagating through optical turbulent structures larger than or of order size diameter. This tip/tilt causes dynamic, net deflection in far field, referred to as jitter, which poses serious problem for tracking directed energy applications. practical measurement turbulence-induced at altitude challenging since...

Shock waves are a commonly observed phenomenon in transonic and supersonic flow. These nearly discontinuous flow features form as result of disturbances propagating faster than the local speed sound. Across shock wave, properties such pressure, temperature, density can change dramatically. In this paper, effects near due to wave on Shack–Hartmann wavefront sensor (SHWFS) measurements studied experimentally. Experiments were conducted Mach 2 wind tunnel located Aero-Effects Laboratory at...

Shock waves result from turning supersonic or locally flow and in a large change gas properties downstream of the shock. This properties, namely, increase freestream density can affect wavefront laser beam propagating through In this paper, analytic expressions are developed to describe effects these shock on both parallel an angle relative direction. Furthermore, near-field disturbances then brought focus at image-plane using thin lens transmittance function with Fresnel diffraction...

Optical measurements of a hemispherical turret were conducted in both wind tunnel and airborne testing environment to measure aero-mechanical jitter imposed onto laser beam. A was positioned the freestream flow at various protrusion distances, Mach numbers, azimuthal angles. Lasers accelerometers used quantify mechanical contamination beam due fluid-structure interaction incoming protruding body. The results from in-flight compared. It shown that tests yielded different quantitatively...

In the typical analysis of aero-optical wave-front data, three lowest-order spatial modes (namely, unsteady piston as well and tilts) are removed from experimentally measured wave fronts. These commonly corrupted by mechanical disturbances. this work, an algorithm called stitching method was developed that takes advantage advective nature optical aberrations caused turbulent structures to recover global X-tilt experimental time-resolved One-dimensional modeling related uncertainty showed for...

We develop a phase reconstruction algorithm for the Shack–Hartmann wavefront sensor (SHWFS) that is tolerant to discontinuities, such as ones imposed by shock waves. In practice, this identifies SHWFS locations where resultant tilt information affected and improves in these using local observation-plane irradiance patterns. The was shown work well over range of conditions tested with both simulated experimental data. turn, will enable robust sensing transonic, supersonic, hypersonic environments.

This work focused on the experimental characterization of a complex flow structure behind cross-flow array cylindrical pins installed wall supersonic duct. geometry simulates several common gas dynamic configurations, such as mixer, turbulence-generating grid, or, to some extent, grid fin. In this work, instrumentation employed is essentially non-intrusive, including spanwise integrating techniques (1) fast schlieren visualization and (2) Shack–Hartmann wavefront sensors; planar techniques,...

This paper serves as part II of a two-part tutorial on "aero-optical effects." In I, we provide introductory material with an emphasis system-level considerations, particularly for those who are new to the field aero-optics. II, move survey several sources aberrations. For example, cover foundational like boundary layers and shear layers, well miscellaneous mechanical contamination, shock waves, aero acoustics. Throughout emphasize drivers performance, which appropriately builds...

An investigation of large-scale boundary-layer structures using optical wavefront sensing techniques is described. Measurements were conducted in Notre Dame’s Tri-Sonic facility at M = 0.4 and 0.5 with a range sampling frequencies spatial resolutions as well the Merill Wind Tunnel Caltech 0.03. In this paper we present several for determining energy spectra implications those to structures. Finally investigate effect Reynolds number on turbulent boundary-layer. The data has shown an increase...

Surface pressure measurements were taken on a hemisphere-on-cylinder turret in wind tunnel using sensitive paint and fast response transducers. Four different protrusion distances tested to study the characteristics of unsteady field backside wake turret. Proper orthogonal decomposition was used identify dominant spatial surface modes acting this parametric study. It found that further protruded into freestream flow, more became dominated by spanwise antisymmetric distributions resulting...

This paper develops a phase reconstruction algorithm for the Shack–Hartmann wavefront sensor that is tolerant to sharp gradients, such as ones imposed by shock waves. The implications of this will enable robust sensing in transonic, supersonic, and hypersonic environments using sensor.

Wind tunnel experiments were conducted to measure the unsteady surface pressure field of a hemisphere-on-cylinder turret in subsonic flow. These measurements obtained using transducers coupled with fast response sensitive paint. The data resulting from Mach 0.5 flow (ReD ≈ 2 × 10⁶ ) over three different protrusion distances analyzed. Previously, dominant modes on found proper orthogonal decomposition. results which showed that greater into freestream increased prevalence spanwise...

This paper serves as Part II of a two-part tutorial on ``aero-optical effects.'' In I, we provide introductory material with an emphasis system-level considerations, particularly for those who are new to the field aero-optics. II, move survey several sources aberrations. For example, cover foundational like boundary layers and shear layers, well miscellaneous mechanical contamination, shock waves, aero acoustics. Throughout emphasize drivers performance, which appropriately builds...

This paper serves as Part II of a two-part tutorial on ``aero-optical effects.'' In I, we provide introductory material with an emphasis system-level considerations, particularly for those who are new to the field aero-optics. II, move survey several sources aberrations. For example, cover foundational like boundary layers and shear layers, well miscellaneous mechanical contamination, shock waves, aero acoustics. Throughout emphasize drivers performance, which appropriately builds...

This paper serves as Part I of a two-part tutorial on ``aero-optical effects.'' We first present background information to assist with our introduction the topic. Next, we use aerodynamic environment associated hemisphere-on-cylinder beam director decompose resulting aberrations (that arise due aero-optical effects) in terms piston, tilt, and higher-order phase errors. also discuss performance implications that these errors have airborne-laser systems. Recognizing complexity environments,...

This paper serves as Part I of a two-part tutorial on ``aero-optical effects.'' We first present background information to assist with our introduction the topic. Next, we use aerodynamic environment associated hemisphere-on-cylinder beam director decompose resulting aberrations (that arise due aero-optical effects) in terms piston, tilt, and higher-order phase errors. also discuss performance implications that these errors have airborne-laser systems. Recognizing complexity environments,...

Disturbances such as atmospheric turbulence and aero-optic effects lead to wavefront aberrations, which degrade performance in imaging laser propagation applications. Adaptive optics (AO) provide a method mitigate these by pre-compensating the before propagation. However, development testing of AO systems requires aberration data, is difficult expensive obtain. Simulation methods can be used generate data less expensively. For turbulence, Kolmogorov-Taylor model provides well-defined power...