Jacques Massoni

Toward a Thermal Disequilibrium Multiphase Model for High Explosives Containing Metallic Particles

To investigate the effects of explosive composition on Al combustion, in particular regarding its oxygen balance, several liquid mixtures are experimentally studied with varying oxygen balance. They are then loaded with Al particles and the velocity of detonation (VOD) is recorded. Computational results with the help of conventional Chapman Jouguet (CJ) codes are compared but fail to reproduce experimental observations. A new multiphase flow model out of thermal equilibrium is then considered. Two options are considered as limiting cases: stiff thermal relaxation and vanishing heat exchange between Al and detonation products. With this last option, predictions are in excellent agreement with the experiments. This suggests that temperature disequilibrium plays a major role in heterogeneous explosives detonation dynamics.

Modeling hyperelasticity in non-equilibrium multiphase flows

The aim of this article is the construction of a multiphase hyperelastic model. The Eulerian formulation of the hyperelasticity represents a system of 14 conservative partial differential equations submitted to stationary differential constraints. This model is constructed with an elegant approach where the specific energy is given in separable form. The system admits 14 eigenvalues with 7 characteristic eigenfields. The associated Riemann problem is not easy to solve because of the presence of 7 waves. The shear waves are very diffusive when dealing with the full system. In this paper, we use a splitting approach to solve the whole system using 3 sub-systems. This method reduces the diffusion of the shear waves while allowing to use a classical approximate Riemann solver. The multiphase model is obtained by adapting the discrete equations method. This approach involves an additional equation governing the evolution of a phase function relative to the presence of a phase in a cell. The system is integrated over a multiphase volume control. Finally, each phase admits its own equations system composed of three sub-systems. One and three dimensional test cases are presented.

Multi-Model Formulation for Compressible Multiphysics and Multiphase Flows: An Efficient Coupling Algorithm

A coupling between a general multiphase flows model and a two-phase dilute flow model is presented. Both models are based on Eulerian approach (two fluids models) and compressible flows are considered. This coupling permits to solve problems in which a multiphase description (involving N phases) is necessary to obtain a good physical behavior of the flow on short times: it corresponds to a given location on the computational domain. Then the flow is developing and far from the location of the initial establishment of the flow, a simpler model can be used, for example a dilute two-phase model one. A methodology for coupling both models is necessary in order to get efficient calculations and a physical consistency. This coupling is not only a challenge regarding the computing resources or the programming. We also require that the wave patterns are correctly transmitted through the coupling interface. We then developed specific Riemann solvers that allow the transmission of acoustic or material waves. We also require the preservation of the conservative quantities such as mass, momentum and energy. The method is checked on ID case: propagation of uniform flows, shock tubes. Multidimensional problem are also presented, showing the efficiency of the coupling methodology regarding CPU time.Copyright