Airframe Drag Computation and Validation of an AH-64

BCFD (Boeing CFD) computations of airframe (or fuselage) drag of an AH-64 helicopter are presented and compared with high-quality wind tunnel test data. These computations use a steady state implementation of the solver for different components of the airframe. The BCFD solver has also been tailored for subsequent drag reduction applications. Drag predictions were made for each component of the airframe including fuselage canopy, EFAB, wing stores, main rotor hub, etc. and their overall contributions to airframe drag for the primary mission configuration to help arrive at low drag design drivers. The CFD predictions have been validated extensively against the 16 percent model scale test data obtained in the University of Washington Wind tunnel to establish the accuracy as well as viability of CFD as a design tool to reduce the airframe drag associated with a complex geometry such as Apache. Further improvements of drag prediction are made using EPIC (Edge Primitive Insertion Collapse) adaptive grid tool.