Magnus Moment Calculation of M910 Spinning Projectiles

Tactical weapons such as missiles, rockets, and artillery shells (referred to as missiles and arrows) typically use a spinning flight mode around their body axis during flight to improve their flight stability. However, when the angle of attack and rotation exist at the same time, due to the distortion of the flow field boundary layer and centrifugal force factors, the pressure distribution on both sides of the missile body is asymmetric, resulting in an additional lateral force—Magnus force. The Magnus force is generally small, about 1–10% of the normal force, but the resulting Magnus torque can affect the directional dynamic stability of the projectile and reduce the shooting accuracy. Therefore, accurate prediction of spinning aerodynamic characteristics becomes an inevitable requirement for missile design, ballistic calculation and stability research. However, due to complex aerodynamic disturbances, such as the coupling of low-speed wake flow and forced rotational motion, the aerodynamic forces and moments acting on the projectile exhibit strong nonlinear and unsteady characteristics, posing a challenge for accurately predicting the aerodynamic characteristics of the projectile. Liu Zhou et al. found that there is a certain difference between the calculation results of the RANS equation for high-speed spinning projectiles with a large angle of attack range and experimental data. The calculation results using the Delayed Separation Eddy Simulation (DDES) method have shown significant improvement. Comparative studies have shown that the position of the separation point has a significant impact on the Magnus effect. This indicates that the DDES method has great potential for improving the numerical simulation accuracy of the Magnus effect of spinning projectiles. The main purpose of this article is to compare the applicability of the RANS turbulence model and the DDES turbulence model for numerical simulation of spinning projectiles. The numerical simulation of a high-speed spinning M910 projectile was conducted. From subsonic to supersonic speeds, the results calculated using RANS method for normal force, pitch moment, normal force center of pressure, and roll damping are in good agreement with experimental data, with a deviation of within 10%. The calculation results showed that for the Magnus moment, in the subsonic and transonic velocity ranges, the RANS method calculated results were significantly different from the experimental results, while the DDES hybrid method was in good agreement with the experimental results, and had better regularity compared to the DES method. The main difference between the RANS method and the DDES hybrid method is the wake flow. The RANS method produces a steady wake, while the DDES hybrid method produces an unsteady wake.