Accession Number : AD1013250


Title :   LES/RANS Modeling of Aero-Optical Effects in a Supersonic Cavity Flow


Descriptive Note : Technical Report,13 Apr 2015,13 Jun 2016


Corporate Author : North Carolina State University Raleigh United States


Personal Author(s) : Zilberter,Ilya A ; Edwards,Jack R


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/1013250.pdf


Report Date : 13 Jun 2016


Pagination or Media Count : 31


Abstract : A hybrid Large Eddy simulation / Reynolds-Averaged Navier-Stokes turbulence model is applied to compute the wavefront aberrations in an optical beam passing through a supersonic open cavity flow. The turbulence model blends a RANS-type closure near solid walls with a subgrid model in the free-stream based on the ratios of estimated inner and outer turbulent length scales. The cavity geometry is modeled using an immersed boundary method, and an auxiliary flat plate simulation is performed to replicate the effects of the wind-tunnel boundary layer on the computed optical path difference. Two-dimensional proper orthogonal decomposition modes of the optical wavefront are computed; these compare favorably with wind tunnel data despite uncertainties about inflow turbulence levels and boundary layer thicknesses over the wind tunnel window. Dynamic mode decomposition of a planar wavefront spanning the entire cavity reveals that wavefront distortions are driven by shear layer oscillation at the Rossiter frequencies; these disturbances create eddy shocklets that propagate into the free-stream and create additional optical path disturbances.


Descriptors :   EDDIES (FLUID MECHANICS) , OPTICAL PHENOMENA , computational fluid dynamics , NAVIER STOKES EQUATIONS , SUPERSONIC WIND TUNNELS , TURBULENT FLOW , SUPERSONIC FLOW , wave propagation , cavities , TURBULENT BOUNDARY LAYER , REYNOLDS NUMBER , LASERS , DIFFUSERS


Distribution Statement : APPROVED FOR PUBLIC RELEASE