A CFD investigation of grid fin missiles

Abstract

This paper presents a numerical study of aerodynamic characteristics of ogivecylinder missiles with and without conventional fins, as well as missiles equipped with grid fin type control surfaces. Both Euler and Navier-Stokes equations are used to describe the flow, which are then solved using the NPARC code on structured multi-block grids. Numerical results obtained for an ogive cylinder show that Euler equations are able to predict shock, the attached flow and aerodynamic loads at small angles of attack. On the other hand, NavierStokes equations in conjunction with a turbulence model have to be used to obtain accurate prediction of missile body aerodynamics and separation induced vortex at a large angle of attack. Numerical results obtained, demonstrate that Euler equations are accurate enough to predict planar fin and grid fin missile aerodynamics of attached supersonic flows. The numerical prediction of normal force coefficients shows good agreement with the experimental data available in literature. The agreement between Euler prediction and experiment also confirms that the present grid fin box does not interfere with each other for moderate angles of attack, and grid fin type control surfaces may be more advantageous for generating relatively higher normal force coefficients (CN) and smaller hinge moments.