Sabot Discard Characteristics under Different Spin Rates of the Rifled Barrel Launching APFSDS

The sabot discard asymmetry caused by spinning affects the exterior ballistic characteristics and shooting accuracy of a gun with the rifled barrel. To gain a deeper understanding of the complex sabot discard performance for the armor-piercing, fin-stabilized discarding sabot (APFSDS), a numerical investigation is performed to assess the effects of the spin rate on the sabot discard characteristics. We obtain the calculation boundary by the interior ballistics and the firing conditions and carry out a numerical simulation under different spin rates using computational fluid dynamics (CFD) and a dynamic mesh technique. We analyze four aspects of sabot discard characteristics, namely, sabot separation, rod surface pressure, rod aerodynamic parameters, and discarding quantization parameters. Computational results show that the sabot separation nearly presents perfect symmetry at 0rad/s, and when the initial rate of the sabot increases, there is more obvious separation asymmetry, and it contributes to the relative position variation among the sabots and the rod. The distinction of rod surface pressure indicates that the choked flow is the strongest flow source, and the spin rate has almost no effect on the pressure of the rod front part. When the monitoring point moves towards the fins, the pressure distribution and intensity change more dramatically. The initial spin rate and separation asymmetry produce a variation in the surface pressure, which further influences the rod aerodynamic characteristics. The discarding quantization parameters exhibit a certain variation rule with its spin rate. 2,000rad/s has a significant influence on the rod aerodynamic coefficients during the weak coupling phase. When the spin rate is in the range of 0-900rad/s, the discarding characteristics remain the same. However, when the spin rate exceeds 900rad/s, the separation time and aerodynamic impulse have a quadratic polynomial relationship with the rate. Additionally, a spin rate of 1,000rad/s is the optimal value for a rifled barrel gun.