Simulation of Combustion of C/B Clouds in Explosions

Abstract

We have developed adaptive high-resolution methods for numerical simulations of turbulent combustion of chemical/biological (C/B) clouds in thermobaric explosions. The code is based on our (Adaptive Mesh Refinement) technology that was used successfully to simulate distributed energy release in explosions, such as: afterburning in TNT explosions and turbulent combustion of Shock-Dispersed Fuel (SDF) charges in confined explosions. Versions of the methodology specialized for low-Mach number flows have also been developed and extensively validated on a number of laboratory scale laminar and turbulent flames configurations. In our formulation, we model the gas phase by the multi-component form of the reacting gas-dynamics equations, while the particle-phase is modeled by continuum mechanics laws for 2-phase reacting flows, as formulated by Nigmatulin. Mass, momentum, and energy interchange between phases are taken into account using Khasainov's model. Both the gas and particle phase conservation laws are integrated with their own second-order Godunov algorithms that incorporate the non-linear wave structure associated with such hyperbolic systems. Specialized ordinary differential equation (ODE) methods are used to integrate chemical kinetics and interphase terms. Adaptive grid methods are used to capture the energy-bearing scales of the turbulent flow (the MILES approach of J. Boris) without resorting to traditional turbulence models. The code is built on an framework that manages the grid hierarchy. Our work-based load-balancing algorithm is designed to run efficiently on massively-parallel computers. Gas-phase combustion in the explosion products (EP) cloud is modeled in the fast-chemistry limit, while Aluminum particle combustion in the EP cloud is based on the finite-rate empirical burning law of Ingignoli. The thermodynamic properties of the components are specified by the Cheetah code. At the 19th HPCUG meeting in 2009, we summarized recent progress in: AMR Code Simulations of Turbulent Combustion in Confined and Unconfined SDF Explosions. These models were used successfully to simulate the simultaneous after-burning of booster products and combustion of Aluminum (Al) in SDF explosion clouds. Computed pressure histories were shown to be in excellent agreement with the data -- thereby proving the validity of our combustion modeling of such explosions. This year, the modeling has been extended to include the mixing and combustion of C/B clouds in such explosion fields. Here we will establish how the cloud consumption by combustion depends on chamber environments.