Numerical investigation of aerodynamic characteristics of free-spinning tail projectile with canards roll control

To reduce aerodynamic coupling between the canards and the tail fins of a canard-controlled projectile, the afterbody of the projectile is decoupled from the forebody by a bearing structure, namely, a free-spinning tail. A series of numerical simulations was conducted for different angles of attack using NASA’s canard-controlled projectile with a free-spinning tail. The results were then compared with the wind tunnel test data. The spin rate of the free-spinning tail shows that, with the canard roll control, the tail section will rotate at lower angles of attack and “lock-in” at higher ones, demonstrating nonlinearization between the rotating rate and the angle of attack. According to a flow structure analysis, the circular flow velocity induced by canards is responsible for the non-linear characteristics of the tail. Moreover, the change in position of the circular flow velocity results in a reverse of the rolling moment of the “+” fixed tail projectile at different angles of attack. Furthermore, a comparison of the aerodynamic characteristics of the fixed (“+” and “x”) and free-spinning tail configurations proves that when the tail is spinning, all the aerodynamic coefficients of the free-spinning tail projectile are between those of the “+” and “x” fixed tail projectiles. The longitudinal difference in aerodynamic characteristics is related to the rolling angle, whereas the lateral difference is related to both the rolling angle and rotation rate. When the tail section “locks-in,” different rolling angles lead to different characteristics in both the longitudinal and lateral directions.