No abstract

Based on the theory of rigid body kinematics, a double slapping theoretical model is established for supercavitation projectile. And a parabolic simplification model is used for replacing the supercavitation equation in the part region of the cavity. Meanwhile, a time interval of two slapping impacts formula is derived from the parabolic simplification model. Then, the Logvinovich bubble expansion equation is discretized by using the Compound Simpson Formula and the cavity cross-section area of the projectile tail is solved in the condition that the projectile decelerates movement underwater. And, the cavity radius value of the projectile tail is obtained from Logvinovich bubble expansion equation, and it is substituted into the time interval formula. Compared with the experimental results, it demonstrates the rationality of the parabola simplification model and time interval formula. The projectile slapping impact, which is the main mode of motion in the cavity, is closely related to the stability of the underwater trajectory. This conclusion has a specific significance for studying the instability of the underwater trajectory.

The traditional supercavitation projectile depends on its kinematics to damage targets. However, the bullet penetration ability is greatly restrained by the range. To improve the damage performance of underwater projectiles, the shaped charge and supercavitation technology are combined in this paper, which called shaped charge supercavitation projectile. The projectile is designed and analyzed through ANSYS/LS‐DYNA software in the preliminary stage. The simulation results turn out that the structures have many advantages with reasonable design. The paper divides the design into three steps: the first step is to design the shaped charge according to the requirements or shaped charge structure designed; the second step is to determine the optimum stand‐off that is obtained by numerical analysis. The stand‐off is set as the length of the projectile head; the third step is to calculate the cavitator diameter by the Logvinovich equation. These results will provide a new idea for the design of underwater weapons.

The water condition usually is complicated due to many uncertain factors such as internal wave, density differences and so on. So the real cavity boundaries is hard to predict for a supercavition projectile. In this work, a random disturbance model is established based on Poison process of random mathematics. This model is employed to the Logvinovich cavitation expansion equation for simulating a cavity in real ocean environment. A detail of cavity outline is obtained by this calculation. The results indicate that the cavitation boundary of higher velocity case is smoother than lowers. The parameter λ of Poison model is a key factor of disturbance frequency, which largely affects the length of cavity. The λ is proportion to the cavity length. This provides a new method for water environment cavity analysis.

Reliability index assignment is an important process in reliability design. On account of some engineering designers with less experience and irrationality for reliability index assignment, according to the characteristics of small-caliber artillery ammunition, the efficient principle and methods are introduced for adaption of the reliability index assignment in this paper. Taking the modification process in developing an aero demolition and incendiary bomb as an example, to analyze and improve tactical and technical indexes such as reliability and blasting power, the reliability index assignment and calculation were carried out by experts grading method for the reference to application