Numerical simulation of the muzzle flows with base bleed projectile based on dynamic overlapped grids

• The implementation of dynamic overlapped grids for muzzle flows is successful.
• The muzzle flows has the characteristics of strong discontinuity and severe chemical reactions.
• The velocity of base bleed projectile increases rapidly, and then begins to decrease gradually with time.
• The rate of depressurization in the combustion chamber of base bleed unit is about 104 MPa/s.
• The average rate of depressurization increase with the increase of the initial pressure of propellant gas.

Numerical investigations of the launch process of a base bleed projectile from the muzzle to free-flight stage have been performed in this paper. A dynamic overlapped grids approach was applied to deal with the problems of a high-speed moving base bleed projectile. A high-resolution upwind scheme (AUSMPW+) and detailed reaction kinetics model were employed to solve the chemical non-equilibrium Euler equations for dynamic grids. A typical case was calculated for the verification of the dynamic overlapped grids approach and numerical methods solving the chemical non-equilibrium flows. After good agreement was achieved, the development process of muzzle flows with high-speed moving base bleed projectile and the rapid depressurization process in the combustion chamber of base bleed unit are discussed in detail. This present numerical study confirms that complicated transient phenomena exist in the early launch stages after the base bleed projectile moves from the muzzle of cannon to the free-flight stage. The base bleed unit of projectile undergoes a strong non-steady-state rapid depressurization. This paper is a significant investigation for understanding muzzle flows with base bleed projectile and rapid depressurization in the combustion chamber of base bleed unit, which can provide valuable reference data for research on combustion stability of the propellant in the combustion chamber.