Two-phase vorticoacoustic flow interactions in solid-propellant rocket motors

Two-phase flow interactions with vorticoacoustic oscillations in simulated solid-propellant rocket motors have been studied numerically using a combined Eulerian-Lagrangian approach. The model accommodates the complete conservation equations in axisymmetric coordinates and, consequently, allows for a detailed treatment of particle dynamics and unsteady motor internal flow evolution. Emphasis is placed on the interphase coupling between the gas and particle fields under the influence of acoustic excitation and turbulence dispersion and the intraphase interactions among particles such as collision and coalescence. The study demonstrates that acoustic oscillations provide additional mechanisms to transfer energy from periodic motions to turbulence, leading to an enhanced level of turbulence intensity and an early transition from laminar to turbulence. On the other hand, turbulence-induced eddy viscosity tends to suppress vortical flow motions caused by acoustic waves. The thermal and momentum relaxation times of particles, along with acoustic characteristic time, play an important role in dictating the two-phase flow interactions with oscillatory motor internal flows. A maximum attenuation of acoustic waves occurs when those timescales become comparable. Small particles, however, usually exert greater influence on the dispersion of acoustic wave through its effective modification of mixture compressibility. Particle intraphase interactions are significant mainly in situations with a wide range of particle size distribution.