NavierStokes Simulations of Unsteady Transonic Flow Phenomena
Abstract
Numerical simulation of two classes of unsteady flows are obtained via the NavierStokes equations: a blast wave/target interaction problem class and a transonic cavity flow problem class. The method developed for the viscous blastwave/target interaction problem assumes a laminar, perfect gas implemented in a structured finitevolume framework. The approximately factored implicit scheme uses Newton subiterations to obtain the spatially and temporally secondorder accurate time history of the interaction of blastwaves with stationary targets. The inviscid flux is evaluated using either of two upwind techniques, while the full viscous terms are computed by central differencing. Comparisons of unsteady numerical, analytical, and experimental results are made in two and threedimensions for Couette flows, a starting shocktunnel, and a shocktube blockage study. The results show accurate wave speed resolution and nonoscillatory discontinuity capturing of the predominantly inviscid flows. Viscous effects were increasingly significant at large postinteraction times. While the blastwave/target interaction problem benefits from highresolution methods applied to the Euler terms, the transonic cavity flow problem requires the use of an efficient scheme implemented in a geometrically flexible overset mesh environment. Hence, the Reynolds averaged NavierStokes equations implemented in a diagonal form are applied to the cavity flow class of problems. Comparisons between numerical and experimental results are made in twodimensions for free shear layers and both rectangular and quieted cavities, and in threedimensions for Stratospheric Observatory For Infrared Astronomy (SOFIA) geometries. The acoustic behavior of the rectangular and threedimensional cavity flows compare well with experiment in terms of frequency, magnitude, and quieting trends. However, there is a more rapid decrease in computed acoustic energy with frequency than observed experimentally owing to numerical dissipation. In addition, optical phase distortion due to the timevarying density field is modelled using geometrical constructs. The computed optical distortion trends compare with the experimentally inferred result, but underpredicts the fluctuating phase difference magnitude.
 Publication:

Ph.D. Thesis
 Pub Date:
 1992
 Bibcode:
 1992PhDT........68A
 Keywords:

 BLAST WAVES;
 CAVITY FLOW;
 Engineering: Aerospace; Computer Science; Physics: Fluid and Plasma