Abstract
The diagonal implicit algorithm has been examined for high speed, moderate density flows. In this flight regime, nonequilibrium thermal, chemical, and radiative effects are important and the determination of these finite rate processes, coupled with a three dimensional flowfield solver, can require large co MP utational resources. In order to minimize computational costs, Irfflay et al. proposed a diagonal implicit solution algorithm. For the extreme conditions of planetary return examined in this report, the avalanche ionization phenomenon gave rise to fast chemical reactions in the stagnation region. The diagonal implicit algorithm was found to give unsafisfactory convergence rates in this region due to numerical instabilities, even at reduced CFL numbers. Thus, the diagonal implicit approximation is not feasible for flows with fast chemical reactions. In addition, changes in the atom impact ionization rates for nitrogen were found to significantly affect the flowfield properties and radiative heat transfer.
Roy, Christopher John (1994). Viability of the diagonal implicit algorithm for hypersonic flowfields with finite rate chemistry. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -R888.