AIAA-2004-6827-168 - AIAA 2004-6827 USAF Developmental Test...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Vice President & Director of Research, Dr. James D. Trolinger, 2572 White Rd., Irvine, CA. 92614, AIAA Associate Fellow President, Dr. William C. Rose, P.O. Box 5146, Incline Village, NV, 89450, AIAA Associate Fellow 1 American Institute of Aeronautics and Astronautics TECHNIQUE FOR SIMULATING AND EVALUATING AERO-OPTICAL EFFECTS IN OPTICAL SYSTEMS J.D. Trolinger, MetroLaser, Inc., Irvine, CA W.C. Rose, Rose Engineering and Research, Inc., Reno, NV This paper describes a new computer model and code that was developed as a quick-look tool for augmenting CFD and experimental aero-optical investigations. The code exploits existing empirical and theoretical knowledge about turbulent shear and boundary layers, turbulence statistics, and relevant optical properties of turbulent flow. It is designed to simulate aero-optical effects on light propagating through various types of aerodynamic flow fields, exploiting the ability of computers to easily mimic random media. This enables optical propagation experiments through relevant types of random optical media to be performed quickly in the computer. The resultant aero-optics computational test simulator enables a systems or test designer to simulate and run aero-optical tests that will be useful for systems evaluations, comparisons, test planning, instrument set up, and data analysis and interpretation. In this paper we show how simple exercises and experiments performed with the simplest variant of the code provide interesting and useful answers relevant to aero-optical effects. I. Background Aero-optics is the science that deals with (usually unwanted) effects on an electromagnetic wavefront caused by aerodynamics 1 . These wavefront effects are caused by refractive index variations that occur in aerodynamic flow fields and distort the wavefront by delaying or advancing parts of it by differing amounts. For most gases, index-of-refraction fluctuations are proportional to the fluid density fluctuations through the Gladstone-Dale constant, which strongly depends upon gas type and weakly on temperature. In this discussion we will essentially speak of density variations and refractive index variations interchangeably. Refractive index variations in a turbulent flow can be the result of temperature gradients, pressure gradients, or non-uniform mixing of different gases, depending on the scenario and type of turbulence. Many types of optical systems (i.e., designators, rangers, LIDAR, laser communicators, directed energy weapons) receive or project light through an aerodynamic flow field, which effectively inserts an unwanted, time-varying, optical element into the system leading to loss of resolution, boresight error, tracking error, reduction in signal to noise, and reduced energy density on a target. The capability of almost all of these devices is deteriorated by aero-optical effects on the optical wavefront caused by flow features of the aircraft, such as shear and boundary layers. These problems have been observed in many flight and
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/10/2012 for the course AFGC-UF 4001 taught by Professor Fielding during the Spring '11 term at Hawaii Pacific.

Page1 / 7

AIAA-2004-6827-168 - AIAA 2004-6827 USAF Developmental Test...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online