Multiphase Flow and Load Characterization of Active Ventilation for Successive Underwater Projectile Launch

Active ventilated bubble technology can enhance the underwater launch trajectory stability and safety of the projectile. This work investigates the multiphase flow and load characterization of active ventilation for successive underwater projectile launch. This paper uses the enhanced delayed detached eddy simulation model coupled with the energy equation, the volume of fluid method, and the overlapping grid technique to simulate the refinement of the ventilated cavitation for successive underwater projectile launch. In addition, the numerical simulations performed in this work agree well with the experimental results, which verifies the efficacy of the simulation. Detailed discussions are presented on transient flow structure and load characteristics. Results indicate that the multibeam ventilation cavity rapidly covers the area below the orifice on the shoulder of the projectile. A contrast with a single underwater launching process shows that the time needed for the cavity flow to completely cover the area below the orifice is approximately the same. When the cavity bubble completely wraps around the projectile surface in a ventilation volume of 0.015 kg/s, a lateral launch spacing twice the diameter of the projectile, and a time interval of 0, the amplitude of the transverse load and alternating peaks decrease. This condition also significantly reduces the resulting deflection moment for double-shot projectiles, especially between the narrow watershed produced by the interference effects. However, within the dimensionless launch intervals ranging from 0.25 to 1, the bubbles in the ventilated cavity completely encapsulate the surface below the orifice. This phenomenon mainly improves the pulsation characteristics of the loads, which is notably through damping the axial force to some extent. However, the enhancement in motion attitude is poor.