The Numerical Simulation Study On Spinning And Pitching Aerodynamic Characteristics Of Projectiles

Flying with spinning or pitching is familiar in projectiles such as rockets and missiles,and the aerodynamic effect induced by the two motions has received increasing attention.This paper is mainly about the spinning and pitching aerodynamic characteristics of projectiles.Firstly,to study the effect of transition on the aerodynamic characteristics of a pointed cone at small angles of attack in supersonic flows,the?-Re?_t transition model,?transition model,and a trip wire applied with?-Re?_t transition model coupled with Reynolds-averaged Navier-Stokes equations were used to simulate the flow fields of the spinning cone.The effect of turbulence intensity,angle of attack and spin rate on the transition of spinning cone were analyzed in this paper,and then the effect of transition on Magnus effect by comparison of boundary layer thickness and velocity profile.The?transition model including the effects of crossflow instability is better than other models in transition and Magnus force prediction.The numerical calculations compared with wind tunnel results indicate that,the positions of the maximum boundary layer thickness remain unchanged using different turbulence models,while that of transition shift towards spin direction,intensifying the difference of the boundary layer thickness between the right and the left side bodies;the contribution of skin friction on Magnus force increases due to the shift of transition position;the contribution of pressure on Magnus force also changes with the distortion of the boundary layer.Secondly,to study the unsteady aerodynamic effect of the projectile with forced oscillation,the realizable k-?coupled with dynamic mesh were used to simulate the flow fields of pointed cone and ANF.Two familiar identification methods were adopted to figure out the pitch damping coefficient.The results indicate that,the numerical results of pitch damping coefficient coincides well with experiment results in supersonic.The dependence of pitch moment on fluctuation amplitude is nonlinear,thus only the method II which accounts for the nonlinear effect could be used to compute the pitch damping coefficient.Fourier transform was used to analyze the distributed normal force coefficient along the projectile longitudinal axis induced by pitching motion.The results indicate that the time-averaged normal force is positive related to angle of attack and is independent on amplitude.The oscillation value of normal force coefficient is proportional with pitching amplitude,but the corresponding phase remains unchanged.