| Popis: |
OVERFLOW-aeroOptics is a specialized version of the OVERFLOW 2.1x overset CFD solver that has been developed to study aerodynamically-induced aberrations to optical wave forms as they are propagated through an unsteady, compressible and turbulent flow field. To achieve this capability a reduced form of Maxwell’s equations, the Paraxial Beam equation, is solved concurrently with the Navier-Stokes equations to propagate a given wave form through the CFD generated density field. The Paraxial Beam equation is solved by a spectral/parabolic operator splitting method, and uses the unsteady CFD density field, typically produced by Large Eddy Simulation (LES) or Detached Eddy Simulation (DES). The integration with OVERFLOW is made through a Fortran90 module that contains procedures that are invoked by the master OVERFLOW process. A collection of postprocessing utilities are provided to produce optical quality metrics that may be used to characterize the effects of flow treatment devices upon aero-optical transmission quality. In this paper we outline the spectral/parabolic approach taken to solve the Paraxial Beam equation and show how this has been integrated with OVERFLOW. Validation is made by performing a mesh refinement study and comparing computed to exact solutions for the propagation of a Gaussian beam through a vacuum. A Top-Hat profile is propagated through a density field corresponding to an isotropic, turbulent flow, and compared to the AOQ Aero-Optics model. We demonstrate the approach by computing the unsteady wave forms as they are propagated through twoand three-dimensional compressible shear layers modeled using Detached Eddy Simulation, and show the beam distortion in the nearand far-fields. |
