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Purpose Various simplifications are introduced into the establishment of numerical models for problems with strong nonlinear interactions. The combustion of energetic materials in a chamber with moving boundaries is a typical example. This paper aims to establish a coupled numerical model for predicting the internal combustion in a launch process. Design/methodology/approach A two-fluid model is used to predict the fluid field induced by the propellant combustion. The moving boundary is located by using a finite element method. Based on a user subroutine interface in the commercial software ABAQUS, the development of the fluid field and the mechanical interactions is coupled with each other. Findings The paper is devoted to provide a coupled computational framework for predicting the propellant combustion in an expanding chamber. The coupling strategy is validated through predicting a pressure-driven piston system. Based on the validated computational framework, the two-phase reactive flows in a launch process is studied. The predicted parameters agree well with experimental measurements. Originality/value This paper provide a method to address the difficulties in realizing the dynamic interactions between multi-phase reactive flows and mechanical behaviors. The computational framework can be used as a research tool for investigating fluid field in a combustion chamber with moving boundaries.

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Methods for improving the accuracy and guaranteeing the fidelity of numerical predictions are of great importance for physical problems accompanied by strong nonlinear multi‐physic interactions and extreme working conditions. The prediction of propellant combustion in a gun launching process is a typical example. A one‐dimensional two‐fluid model was utilized to govern the fluid field induced by the combustion. In order to guarantee the accuracy of the predictions, we utilized a Roe's scheme to solve the partial differential equations. To guarantee the accuracy of the moving boundaries in the expanding chamber, the coupling between the updating of the fluid field and the approximation of the mechanical interactions between the projectile and the barrel is realized based on the commercial software ABAQUS. The separate treatment of the advection and source terms in the split approach was verified through the agreement between the maximum value of the predicted average pressure in a closed bomb and the theoretical value. The coupled method dealing with the moving boundaries was validated by comparing the numerical results with the analytical results of a pressure‐driven piston case. Finally, the numerical method was applied to a large‐caliber gun. The predicted maximum pressure and the muzzle velocity agree well with experiments.

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