Supersonic flow computations for an ASTOVL aircraft configuration

SUPERSONIC FLOW COMPUTATIONS FORAN ASTOVL AIRCRAFT CONFIGURATIONAbstractA unified space/time marching method has been used to solve the Euler and Reynolds-averaged Navier-Stokes equations for supersonic flow past an Advanced Short Take-Off andVertical Landing (ASTOVL) aircraft configuration. Lift and drag values obtained L'omthe computations c()mpm'e well with wind-tunnel measurements. This report describesthe entire calculation procedure starting from the geometry to final postprocessing for liftand drag. The intermediate steps include conversion from IGES to the patch specifica-tion needed for the CFD code, grid generation and solution procedure. Tile calculationsdemonstrate '!_e capability of the method used to accurately predict design pa_met.erssuch as lift and drag for very complex aircraft configurations.IntroductionRockwell Science Center, under contract with NASA Langley Research Center, has beendeveloping very powerful numerical methods for the Euler equations. The research be-gan with the development of upwind schemes of first-order accuracy based on the Osherscheme and progressed to higher order TVD (Total Variation Diminishing) schemes en-compassing a variety of upwind formulations incblding Osher's and Roe's approximateRiemann solvers (Ref. 1). This algorithmic research culminated in the development ofthe EMTAC (Euler Marching Technique for Accurate Computations) code for steady in-viscid supersonic flows including subsonic pocket treatment (Ref. 2). The EMTAC codewas delivered to NASA Langley Research Center in 1987. Rockwell International thendeveloped a multizone capability that was built into the EMTAC-MZ code which wasinitially Rockwell proprietary (Ref. 3). As part of an extension to the original contractwith NASA Langley Research Center, Rockwell agreed to make EMTAC-MZ available toNASA for their use and dissemination. The EMTAC-MZ code and its usage are separatelydescribed in a user manual (Ref. 4). During this period, NASA became very interestedin the study of STOVL configurations (see below) and the EMTAC-MZ was used for thatpurpose. Subsequently, Rockwell Science Center also developed viscous flow capability intheir proprietary USA-series (Unified Solution algorithms) of flow solvers (Ref. 5). It wasdecided as part of the NASA Langley Research Center contract to also demonstrate thefeasibility of Navier-Stokes computations for ASTOVL configrations and this forms thesubject matter here.A rationale for the interest in STOVL configurations may be found in the material quotedhere from Ref. 6. "Operational flexibility of modern fighter/attack aircraft can be signifi-cantly enhanced with vertical flight capability. However, numerous studies have indicatedthat such improvements are minimized due to performance degradations as a result of theVTOL requirement. In an attempt to design an aircraft with military advantages of VTOL,but with minimum performance degradation, General Dynamics under contract to NASA