Aerodynamic Shape Optimization Analysis of Axisymmetric Bullet Based on Response Surface NSGA-II Algorithm

The aerodynamic characteristics of the axisymmetric bullet determine the effectiveness of the final damage purpose. To solve the contradiction problem between the aerodynamic drag coefficient and the objective volume in the design and selection of oval head bullet, four design parameters, namely, head length, body length, and tail length and tail angle, are selected as response factors. They have significant impacts on the aerodynamic performance and volume of the rotating stable axisymmetric bullet. The optimization boundary for these four parameters is established, and the sample space of 30 optimization groups is created by using the response surface method. Through the finite volume simulation of these 30 groups of samples, the corresponding drag coefficient and bullet volume are obtained. The function between the drag coefficient, bullet volume and sample parameters is fitted. Then, the NSGA-II algorithm is combined to conduct optimization analysis on the fitting function, and four response factor combinations on the Pareto boundary are obtained, where the drag coefficient is decreased and the bullet volume is increased. The second derivative of the solution set is analyzed to determine the optimal shape of the oval head axisymmetric bullet. The comparison shows that the drag coefficient of the optimized bullet shape is 13.1% lower than the average drag coefficient of 30 original samples, and the volume is increased by 39.5%. The method, combined the response surface method with NSGA-II algorithm, effectively improves the design efficiency of oval head axisymmetric bullet optimization design.