Application of CFD to a Slender-Bodied, Finned Projectile

The prediction of aerodynamic coefficients for projectile configurations is essential in assessing the performance of new designs. Accurate determination of aerodynamics is critical to the low- cost development of new advanced guided projectiles, rockets, missiles, and smart munitions. Fins, canards, and jets can be used to provide control for maneuvering projectiles and missiles. The flow fields associated with these control mechanisms for the modern weapons are complex, involving three-dimensional (3-D) shock-boundary layer interactions and highly viscous dominated separated flow regions (1–5). Computational fluid dynamics (CFD) has emerged as a critical technology for the aerodynamic design and assessment of weapons. Improved computer technology and state-of-the-art numerical procedures enable solutions to complex, 3-D problems associated with projectile and missile aerodynamics. In general, these techniques have the potential to produce accurate and reliable numerical results for complex projectile and missile configurations.

As part of a U.S. Army Advanced Technical Objective (ATO) for Extended Area Protection System (EAPS), technologies are currently being developed to support future air defense system. The goal for the air defense system is to leverage the best combination of directed energy and/or kinetic energy (KE) capabilities against the aerial threat and achieve the capability to protect the force and high value assets against incoming rockets, artillery, and mortars. Improved lethality, accuracy, and fire control are required for a KE munition-based weapon. Various system technologies are being developed under this ATO to address these issues. Critical technologies that are required to bridge the gap will support enhanced lethality, effective fire control, increased engagement kill probability, and simultaneous engagements of multiple threats. High- fidelity CFD is required in the design process to achieve optimized location of jet and/or other control devices for increased maneuverability of a projectile or a missile. This approach has shown great promise for the optimization and strategic location to achieve the turning force necessary to terminally steer a missile or projectile to its target, thereby increasing the lethality of future combat systems. The first step in the design process is to be able to obtain the full aerodynamics of the projectile. This report presents the results of computational investigation of the aerodynamics of a preliminary EAPS projectile design configuration to be used as a test-bed for electronics development and aerodynamic control authority being developed.

The information presented in this report focuses on the application of CFD to a preliminary design for the EAPS configuration—a slender-body finned projectile. A description of the computational techniques is presented, followed by a description of the applications of these techniques to the computational model. Computed results for the initial configuration are presented for Mach numbers ranging from 1.5 to 5.0 at angles of attack ranging from 0° to 5°. The computed data are compared with semi-empirical data provided by Arrow Tech (6).