Modeling multiphase flow characteristics and particle behavior of mixed charge structure using the particle element method

A mixed charge structure is composed of several different types of particles to achieve performance indicators that cannot be achieved by a single particle and usually need to be adjusted and evaluated to determine the parameters in the chamber according to different demand. To balance the accuracy and efficiency, and obtain more calculation parameters, the solid phase is modeled by the particle element method, while the fluid phase is modeled by a computational fluid dynamics solver based on the fifth-order weighted essentially non-oscillatory scheme. In the mixed charge structure of different granular propellant, different particles in different areas are classified and particle elements are divided, and the particle interface position is tracked and captured to form the particle element distribution with different sizes. In the mixed charge structure with central tubular propellant, the granular and the tubular propellants are calculated separately by different types of particle elements, and the source term is used in coupling simulation. Comparing with the calculation results of experiment, the velocity error is less than 1%, and the maximal breech pressure error is less than 3%. In the mixed granular charge structure, due to the differences in combustion rates and movement velocities of the particles, the distribution state of the particles within the chamber is significantly different from that of single particle charge. Additionally, the standard deviation of the porosity is greater in mixed granular charge (0.051: 0.0086). In the mixed charge structure with central tubular propellant, the porosity of tubular and particle distribution in the chamber is discontinuous, and the pressure distribution is effectively predicted. The calculation results show that the perfect consistency of ignition in the chamber, which shows the superior flame-spreading performance of the central tubular propellant. The particle element method can provide a powerful tool for the rapid modeling and simulation of two-phase flow.