Simulation of complex shock reflections from wedges in inert and reactive gaseous mixtures

Abstract

Our calculations of complex and double Mach reflection are in close agreement with measurements for shocks reflecting in air from wedges. Because of the accuracy and speed of FCT algorithms and the effectiveness of adaptive rezoning, the calculations are accurate and economical even when the Mach stem develops very slowly. All of the important features (location of surfaces of discontinuity, pressure loading on the wedge surface, density contours) are correctly predicted. The results do not depend sensitively on whether the L-T or FAST2D code is used. Of the advances discussed in Section 1, multidimensional flux limiting and the adaptive regridding technique seem to be the most efficacious for reflections in nonreactive media. We conclude that FCT algorithms reduce numerical diffusion dramatically, assuring qualitative improvements in accuracy. We believe that to achieve comparable accuracy and efficiency, other hydrocodes must employ similar nonlinear algorithms and rezoning techniques.

Our calculations in reactive gas mixtures show that detonations tend to begin where a secondary pressure peak arises as the slip surface approaches the wedge. Because of the finite induction time in our kinetics model, the detonation begins somewhat behind this pressure peak. The high resolution our calculations achieve enables us to follow multiple reflections and is capable of providing quantitative predictions of detonation phenomena.

NRL/NRC Postdoctoral Research Associate.

Work supported by the Defense Nuclear Agency and the Office of Naval Research