mm M projectile as shown in Fig a was

155 mm M549 projectile, as shown in Fig. 1(a), was used as an example in the present paper. The micro-vanes were mounted at the projectile shoulder to form a new physical model, as shown in Fig. 1(b). Fig. 2 shows the computational domain of M549 projectile. Fig. 2(a) shows the grid distribution of symmetric surface, and Fig. 2(b) and (c) show the sliding grid near the projectile and the grid near a vane, respectively. The computational domain is divided into an external fixed area and an internal sliding area. The grids within boundary layer were refined along the normal direction, and the grids near the head, shoulder and tail of projectile were refined along the flow direction. After repeated calculations and convergence tests, the grid number of the whole area is about 2 million. Projectile surface is applied with the no-slip wall boundary condition, and the meshes of the interior layers are designed to move with the projectile. The interfaces of external fixed grid area and internal sliding area are adopted with the sliding boundary conditions. The mach number of incoming flow is assumed to be 2.05. The initial pressure P0 is set to 1.014 × 105 Pa, and the initial temperature T0 is 278K. The spin rate of the projectile is chosen to be , which equals a maximal dimensionless spin rate, . The rotation is anti-clockwise viewing from the Adrucil of the projectile.
Results and discussion Fig. 3 shows the comparison of previous measured and simulated side force coefficients of a generic 6.37 diameter long tangential-ogive-cylinder type projectile. The simulated results of unsteady DES method are compatible with the previous simulated and experimental results. It verifies that the credibility of the numerical simulation results in this paper. Fig. 4 shows the pressure distributions on the surfaces of the standard projectile and the projectile with micro vanes and around them with Ma of 2.05 and angle of attack (AOA) of 4°. The main shock wave structures are the same for both cases; there are oblique shock waves around the heads and expansion waves near the tails. But for the projectile with micro-vanes, the oblique shock wave also forms along the micro-vanes, and its strength is much weaker than that of head shock wave. In addition, the shock waves around micro-vanes are stronger at the area close to the windward side, which makes the surface pressure higher than that on the leeward side, and leads to a raise in the projectile lift.
Conclusion
Introduction Using reconnaissance system to obtain the exact coordinates of ground target and providing the target location for weapon systems timely has become an efficient combat mode. A reconnaissance system is used to locate a target, and the target localization information is loaded to an onboard computer before launching a trajectory correction projectile. Currently, UAV [1–3], airborne electro-optical platform [4], and airborne radar or ground radar [5–7] have been used for ground target localization. The localization accuracy of all the localization methods is related to position accuracy of carrier itself and target detection accuracy.
Target localization method The operating principle of semi-active laser terminal correction projectile is that a laser designator is used to irradiate a target, and then a laser spot signal reflected from the target is received by a laser detector, as shown in Fig. 1; a control command is generated based on the reflected signal as input; and finally, according to the control strategy, the trajectory error is corrected by a control force produced by an actuator in projectile.
Solution of localization algorithm According to the target localization principle in Section 2.3, a relevant solution is needed to get the target location since three ellipses cannot intersect at a point. The projectile-target frame OrXrYrZr is obtained by moving the base frame from origin point O to projection point Or of projectile on the ground, and the frame with angle ψ is rotated about the axis of OrYN, as shown in Fig. 6. The center location of ellipse in projectile-target frame can be obtained by the geometrical relationship between optical axis of detector and target, denoted as point E1(xe, 0, 0).