Deflection Head MISSILES Supersonic Flow Field And Aerodynamic Characteristics

The projectile with deflectable nose means that its nose can form an angular deflection away from the axis according to actual condition, therefore, the aerodynamic force which is created by the differential pressure of the windward and leeward of the nose can be used to manipulate the projectile and to control its flight attitude. Due to the advantages of both simple structure and high control efficiency, therefore, researches performed on its control mechanism have profound significances to its corresponding engineering applications.In this thesis, firstly, based on the Euler equation and second-order AUSM scheme, the supersonic flow fields and aerodynamic characteristics of the projectile with deflectable angles of0°、4°、 and8°were simulated numerically under the condition of zero angle of attack and Ma=2.0、3.0、4.0. We find that the deflectable nose has great influence on the aerodynamic characteristics of the projectile especially on the head of the projectile. However, its effects on the downstream flow field of the projectile are small. To avoid the limitation of two dimensional models, the three dimensional flow fields of the projectile with deflectable nose were simulated based on the DES (Detached Eddy Simulation), and we found that, with increase of deflectable nose, the raising gradient of the lift coefficients is larger than that of drag coefficients.Moreover, with the use of same numerical methods, the supersonic flow field and aerodynamic force coefficients of the projectile with deflectable nose were simulated numerically at non-zero angles of attack and different deflectable angles. Our numerical results showed that, when the effective incidences of all projectiles are equal, the structures of their flow fields are all the same, and the flow fields of tail fins are not affected by the nose. From the time history of aerodynamic coefficients versus angles of attack, we find that the projectiles with deflectable noses have good longitudinal stability. Besides, its lift-to-drag ratio is higher than normal projectile.Lastly, investigations on the supersonic flow field and aerodynamic characteristics of the projectiles were conducted under the conditions of high altitude rarefied gases. After comparing with the results of normal low altitudes, we found that the structures of both flow fields are similar. But there are some differences between the aerodynamic coefficients. The coefficients of lift, drag and pitch moment are smaller than corresponding coefficients in low altitudes, therefore, their control efficiencies decrease for high alititudes.