Nonlinear aerodynamic analysis of grid fin configurations

Abstract

The aerodynamic analysis of grid fin configurations has been extended to generic cruciform configurations oriented at any azimuthal angle. The generality of grid fin designs has been retained providing orientations for up to four fins as mounted on or near the surface of a missile airframe. The theoretical analysis is based on a vortex lattice overlay of the lifting elements and includes appropriate body upwash terms as well as wing-body carry over load prediction. This basic approach produces adequate modeling for small angles of attack and small fin incidence angles for any grid fin located at any azimuthal position around the body. For higher angles of attack, empirical equations have been developed for fin coefficients and for the body aerodynamic coefficients. Entire four fin configurations are generically modeled and solutions are obtained in an iterative manner. Excellent agreement between experimental data and theoretical predictions have been obtained for the configuration considered up to angles of attack of twenty degrees and fin incidence angles of thirty degrees. For other grid fin designs other than the one considered in the wind tunnel test and for higher angles of attack, the agreement between the theory and experimental results has not been established.