Simulation of laser propagation through jet plumes using computational fluid dynamics

We have investigated the possibilities of using Computational Fluid Dynamics (CFD) simulations to characterize the impact of refractive index fluctuations in a jet engine plume on Directed InfraRed CounterMeasure (DIRCM) system performance. The jet plume was modelled using both Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) formulations of Navier-Stokes equations. The RANS calculations provided a time-averaged description of the refractive index and the turbulence strength. The more computationally intense LES model provided time resolved data on large scale turbulent eddies within the engine plume. The smaller structures are assumed to be isotropic and are modelled implicitly to reduce the computational demands to levels feasible for current computational hardware. The refractive index data from the CFD calculations was integrated along the optical propagation path to produce phase screens. For RANS data this approach provided time averaged aberrations, whereas for LES data the temporal variation of low spatial frequency aberrations were available for a short time sequence. Modal descriptions of the phase screens were investigated to allow study of temporal variation at longer time scales. Alternatively the structure parameter (Cn2) can be estimated and used to provide order of magnitude approximations for the optical effects. The generated phase screens were used to calculate laser beam system level quality parameters including beam wander, fidelity ratio and power-in-bucket. The paper focuses on method development, but examples of a jet plume simulation showing that the engine plume turbulence has a significant impact on DIRCM system functionality are presented.

[1]  Byron M. Welsh,et al.  Fourier-series-based atmospheric phase screen generator for simulating anisoplanatic geometries and temporal evolution , 1997, Optics & Photonics.

[2]  J. L. Barrett,et al.  Laser beam propagation through strong turbulence , 1992 .

[3]  V. S. Sirazetdinov,et al.  Experimental study and numerical simulation of laser beams propagation through the turbulent aerojet. , 2008, Applied optics.

[4]  Rickard Bensow,et al.  On the justification and extension of mixed models in LES , 2007 .

[5]  Inga V. Ivanova,et al.  Distortions of laser beams by turbulent aero-engine jet: experiment and numerical modeling , 2004, Lasers for Measurements and Information Transfer.

[6]  R. Noll.  Zernike polynomials and atmospheric turbulence , 1976 .

[7]  Arne V. Johansson,et al.  An explicit algebraic Reynolds stress model for incompressible and compressible turbulent flows , 2000, Journal of Fluid Mechanics.

[8]  H Jakobsson.  Simulations of time series of atmospherically distorted wave fronts. , 1996, Applied optics.

[9]  Hrvoje Jasak,et al.  A tensorial approach to computational continuum mechanics using object-oriented techniques , 1998 .

[10]  Christer Fureby,et al.  Numerical laser beam propagation using a Large Eddy Simulation refractive index field representing a jet engine exhaust , 2010, Security + Defence.

[11]  Chris Porter,et al.  Large-aperture approximation for not-so-large apertures , 2013 .

[12]  Mikael Petersson.  Real-time DIRCM system modeling , 2004, SPIE Security + Defence.

[13]  Markus Henriksson,et al.  Laser beam propagation in close vicinity to a down-scaled jet engine exhaust , 2004, SPIE Security + Defence.

[14]  R. Fante,et al.  Electromagnetic beam propagation in turbulent media: An update , 1980, Proceedings of the IEEE.

[15]  Meng Wang,et al.  Resolution requirements for aero-optical simulations , 2008, J. Comput. Phys..

[16]  Offer Padé.  Turbulence modeling by realization of density fluctuations , 2008, Remote Sensing.

[17]  Viktor A. Banakh,et al.  Reconstruction of the structural characteristic of the refractive index and average air density in a shock wave arising in a supersonic flow past obstacles from optical measurements , 2011 .

[18]  Lars Sjöqvist,et al.  Laser beam propagation in jet engine plume environments: a review , 2008, Security + Defence.

[19]  A. Hellsten,et al.  New Advanced k-w Turbulence Model for High-Lift Aerodynamics , 2004 .

[20]  Lars Sjöqvist,et al.  Experimental study of mid-IR laser beam wander close to a jet engine exhaust , 2006, SPIE Security + Defence.

[21]  Parviz Moin,et al.  Statistical description of the free-space propagation of highly aberrated optical beams. , 2006, Journal of the Optical Society of America. A, Optics, image science, and vision.

[22]  Jinhee Jeong,et al.  On the identification of a vortex , 1995, Journal of Fluid Mechanics.

[23]  Nicolas A. Roddier.  Atmospheric wavefront simulation using Zernike polynomials , 1990 .

[24]  Viktor A. Banakh,et al.  Reconstruction of the radial dependence of the structural characteristic of the refractive index in a supersonic gas flow from laser beam intensity fluctuations , 2010 .

[25]  Oskar Parmhed,et al.  CFD Predictions of Jet Engine Exhaust Plumes , 2008 .

[26]  J. Goodman.  Introduction to Fourier optics , 1969 .

[27]  D. H. Titterton.  Measurement of the Distortion Generated in a Laser Beam’s Characteristics Resulting from Passage through an Engine’s Wake , 1998 .

[28]  Lars Sjöqvist,et al.  Laser beam propagation through a full scale aircraft turboprop engine exhaust , 2010, Security + Defence.

[29]  Matthew R. Whiteley,et al.  Spatial and temporal characterization of AAOL flight test data , 2012, Defense, Security, and Sensing.

[30]  Offer Padé.  Propagation through shear layers , 2006, SPIE Remote Sensing.

[31]  B. Uscinski,et al.  Wave propagation and scattering in random media, volume 2: Multiple scattering, turbulence, rough surfaces, and remote sensing: 1978, Akira Ishimaru. New York: Academic Press. 320 (253–572) + xix pp; price £17.50. ISBN 0.12.374702.3 , 1980 .

[32]  David H. Titterton,et al.  Laser beam propagation through a jet aircraft engine's exhaust , 2001, SPIE Remote Sensing.

[33]  Matthew R. Whiteley,et al.  Airborne Aero-Optics Laboratory , 2013 .

[34]  Erik Sucher,et al.  Laser beam propagation experiments along and across a jet engine plume , 2008, Security + Defence.

[35]  Offer Pade.  Optical propagation through turbulent jets , 2004, SPIE Remote Sensing.

[36]  Alan R. Shapiro.  Laser propagation in aircraft wakes , 1993, Optics & Photonics.

[37]  R. Frehlich,et al.  Simulation of wave propagation in three-dimensional random media. , 1995, Applied optics.

[38]  C. R. Viau.  Expendable Countermeasure Effectiveness against Imaging Infrared Guided Threats , 2011 .

[39]  R. Fante.  Electromagnetic beam propagation in turbulent media , 1975, Proceedings of the IEEE.