Session ME - Turbulence Simulations V.
MIXED session, Tuesday afternoon, November 23
Cascade I, Westin Seattle
Spatial variations of refractive index due to density fluctuations in a compressible turbulent flow may cause serious problems for optical systems. In general, distortion by turbulence results in coherence degradation of the optical beam, and leads to loss of intensity at distant locations. The objective of this study is to develop computational capability for aero-optical distortion caused by turbulent boundary layers and wakes around moving objects. In particular, we consider the compressible flow over a circular cylinder at Re_D=3900 and M=0.4. The flow solutions obtained by large-eddy simulation have been validated against previous experimental and numerical results. Ray tracing combined with Fourier optics is chosen as an efficient and accurate tool to simulate optical wave propagation. Statistics of optical aberration and it's correlation to flow motion will be presented. Our results indicate that for short wavelength beams, the far-field intensity pattern is seriously affected by the small scales of the flow, which places a more stringent grid-resolution requirement than that needed to capture the low order flow statistics.
Supported by AFOSR.