Computational Fluid Dynamic (CFD) Analysis of a Generic Missile With Grid Fins

摘要

This report presents the results of a study demonstrating an approach for using viscous computational fluid dynamic simulations to calculate the flow field and aerodynamic coefficients for a missile with grid fin. A grid fin is an unconventional lifting and control surface that consists of an outer frame supporting an inner grid of intersecting planar surfaces of small chord. The calculations were made at a Mach number of 2.5 and several angles of attack for a missile without fins, with planar fms, and with grid fins. The results were validated by comparing the computed aerodynamic coefficients for the missile and individual grid fins against wind tunnel measurement data. Very good agreement with the measured data was observed for all configurations investigated. For the grid fin case, the aerodynamic coefficients were within 2.8-6.5% of the wind tunnel data. The normal force coefficients on the individual grid fins were within 11% of the test data. The simulations were also successful in calculating the flow structure around the fin in the separated-flow region at the higher angles of attack. This was evident in the successful calculation of the nonlinear behavior for that fin, which showed negative normal force at the higher angles of attack. The effective angle of attack is negative on either part of or all of the top grid fin for the higher angles of attack.