Shedding characteristics of tail cavities under vertical launching conditions

Vertically launched cross-media vehicles have attracted growing research interest at the cross field of shipbuilding and aerospace, owing to their high maneuverability and stealth characteristics. Upon exiting the launcher tube, a tail cavity forms and adheres to the bottom wall of the vehicle. During the unsteady evolution of the tail cavity, cavity shedding is a significant flow phenomenon. A deeper understanding of its flow mechanisms and the resulting flow field disturbances is beneficial for controlling tail cavity behavior and improving the vehicle's attitude control. Thus, current work establishes a numerical simulation model for tail cavity shedding, employing a Detached Eddy Simulation model, the Volume of Fluid method, zero-gap overset grids technology. In addition, adaptive mesh refinement is further applied to improve the resolution of the gas–liquid interface. Numerical results are validated against experimental data to demonstrate the accuracy of the numerical method. The results indicate that the tail cavity shedding frequency coincides with the pulsation frequency of the cavity volume. The downstream tail cavity continuously contracts and detaches in a regular ring shape. Subsequently, the reentrant jet induces a velocity difference between the inner and outer sides of the shedding cavity, driving its transition into a vortex-tube structure. In the second shedding cycle, the fluid baroclinic torque causes gradual accumulation of vorticity along the gas–liquid interface. Additionally, the continuous contraction and shedding of the tail cavity result in the ongoing stretching and distortion of vortices. Eventually, the Kelvin–Helmholtz instability along the gas–liquid boundary intensifies, and cavity shedding exhibits nonlinear behavior characterized by the random detachment of vortex tubes. When the Froude number decreases from 2.78 to 1.67, the tail cavity does not rupture to cause cavity shedding. Instead, it rolls upstream and reintegrates directly into the main body of the tail cavity.