Research On Multiphase Flow And Structural Dynamics Of Supercavitating Projectile During Tail-slapping

Due to imperfect water entry or the disturbances that occur during firing, a highspeed supercavitating projectile, while moving in the forward direction, rotates insidethe cavity. This rotation leads to a series of impacts between the projectile tail and thecavity wall. The impacts affect the characteristic of flow field around the body and thestability of trajectory as well as the vibration of the projectile. The present thesisdiscusses the multiphase flow and the structural dynamics of a projectile duringtail-slapping. The main topics of this thesis are as follows:The principle of independence of the cavity sections expansion and theinhomogeneous multiphase flow model are used separately to investigate the cavitatingflow of supercavitating projectile, and the computational methods are verified. Themotion equation of rigid body and no-constrained vibration equation are derived,besides, the change laws of the attitude and vibration response of projectile duringtail-slapping are described.Based on the tail-slapping motion equation and semi-empirical formula of tail load,the attitude of projectile has been calculated and the influences of projectile center massand cavity swing have been given. By simplifying the projectile to an Euler-Bernoullibeam and using no-constrained vibration equation, the vibration response of projectilehas been calculated and the influences of axial pressure and water compressibility aswell as the stiffening rings have been given.By using the inhomogeneous flow model, the multiphase flow field of tail slaps ofprojectile in uniform motion or free deceleration has been simulated. The influences oftail slaps to cavity and hydrodynamic of projectile have been analyzed and the changelaw of tail load has been summarized as well. Based on the simulating results andrelative literatures, a new theory model of tail load has been proposed and verified.Based on the dynamic equations of rigid flexible coupling system, the trajectoryand vibration response of projectile have been calculated by using the new tail loadmodel, the influences of rigid flexible coupling effect have been given. Based on thestaggered solution procedure of ANSYS and CFX software, the fluid structure couplingresponse of projectile during tail-slapping has been simulated, then, the influences offluid structure coupling effect have been analyzed and the change law of body stress has been given.An experiment for the study of free flying supercavitating projectiles has beencarried out, the change of velocity and attitude as well as the trajectory of projectileduring tail-slapping has been researched, and the influences of tail slaps to the cavityand stability of body motion have been analyzed. By comparing with the experimentalresults, the new theory model of tail load proposed in present thesis has been verified.