Towards Numerical Simulation of Shock Induced Combustion Using Probability Density Function Approaches

Abstract

The specific problem to be addressed in this work is the secondary combustion that arises from shock-induced mixing in volumetric explosives. It has been recognized that the effects of combustion due to secondary mixing can greatly alter the expansion of gases and dispersal of high-energy explosive. Furthermore, this enhanced effect may be a tailored feature for the new energetic material systems. One approach for studying this problem is based on the use of Large Eddy Simulation (LES) techniques. In this approach, the large turbulent length scales of motion are simulated directly while the small scales of turbulent motion are explicitly treated using a subgrid scale (SGS) model. The focus of this effort is to develop a SGS model for combustion that is applicable to shock-induced combustion events using probability density function (PDF) approaches. A simplified presumed PDF combustion model is formulated and implemented in the CTH shock physics code. Two classes of problems are studied using this model. The first is an isolated piece of reactive material burning with the surrounding air. The second problem is the dispersal of highly reactive material due to a shock driven explosion event. The results from these studies show the importance of incorporating a secondary combustion modeling capability and the utility of using a PDF-based description to simulate these events.