The Study On Dynamic Characteristics Of Terminal Sensitive Submunition With Parachute

Terminal sensitive submunition with parachute is decelerating and spinning by using nonaxisymmetrical rotating parachute,and finally reaches to the stage of steady scanning.Therefore,the dynamic characteristics of the submunition depend on the whole performance of the nonaxisymmetrical rotating parachute.By combining theoretical analysis,numerical simulation and experimental study,the inflation and aerodynamic characteristics of nonaxisymmetrical rotating parachute system,as well as the trajectory characteristic and kinetic stability of termminal sensitive subnumition with parachute,were studied systematically.The results could offer theoretical basis and technical support to physical design optimization and scanning efficiency improvement of terminal sensitive munitions with parachute,and promotion and application of nonaxisymmetrical rotating parachute system.Taking a typical kind of rotating parachute-vortex ring parachute as study object,the inflation model in straighten state was established.Based on the arbitrary Lagrange-Euler method,the canopy shape change and the time-history curves of canopy projective diameter and spinning rate during the inflation process,as well as the stress and strain distribution of the inflated canopy and the fluid domain changing rules,were obtained.The effects of structural parameters and the inflow velocities on inflation performance and steady spinning rate were analyzed.On the basis of the fluid-structure interaction results,the fluid model of inflated vortex ring parachute was established.Using computational fluid dynamics method,the distribution laws of fluid domain around canopy and the main aerodynamic parameters at steady state were calculated.Based on the scanning requirement and the inflation model structure,the physical model of terminal sensitive subnumition with parachute was designed.Firstly,car towing test was carried out to explore the inflation performance and the resistance features preliminary.Then,tower test was set up.The effects of structural parameters,including the difference of trailing-edge pitch line and leading-edge pitch line and the canopy area,on the decelerating and spinning efficiency of vortex ring parachute were obtained.And a structure optimization method of vortex ring parachute was proposed to increase the ratio of spinning rate and falling velocity.To improve the efficiency further,a tandem compound parachute system composed of a rotating parachute and a round parachute was designed.Considering the practical structure,and based on the Lagrange equations of the first kind,5 rigid-body with 15 DOF dynamic model of terminal sensitive submunition with rotating parachute,as well as 6 rigid body with 21 DOF dynamic model of terminal sensitive submunition with compound parachute,was set up.Through simulation the free falling process with the initial velocity of 0,the availabilities of the two models were verified by tower test.The trajectory characteristics of the two models from the stage of decelerating and despinning to the steady stage of scanning were analyzed and compared.The results show that the two systems could all meet the requirement of steady scanning,and the scanning efficiency of the compound parachute is better than that of the vortex ring parachute.The trajectories affected by different wind fields were solved,and the effects of different wind fields on target-catching probability were analyzed.Considering the connection type of rotating parachute and submunition sufficiently,the angle motion model of terminal sensitive submution with parachute was set up by the rigid-body trajectory equations of 6 DOF and the small perturbation assumption.The angle motion changing laws of rotating parachute and submunition under the conditions of wind and no wind were obtained.The judgment method of the kinetic stability was present,and the effects of structural parameters on the stability were analyzed.