Computational Aerodynamic Analysis for the Formation Flight for Aerodynamic Benefit Program

A summary of the computational aerodynamic performance tools and analyses for the development of the Surfing Aircraft Vortices for Energy (SAVE) formation flight concept is presented. Aerodynamic analysis is accomplished using several, multi-fidelity prediction methods, including a vortex lattice method (VLM) approach, a panel method to model body effects, and a high-fidelity hybrid computational fluid dynamics (CFD) method that couples a Reynolds Averaged Navier-Stokes (RANS) flow solver for the near-body simulation with a quasi-3D RANS approach for the evolution of wakes over long longitudinal distances. Computational analysis is used to develop a comprehensive aerodynamic database for flight simulation and control law design, to develop a drag benefit “map”, which is used to determine the optimum location of the trailing airplane relative to the leading airplane wake, and to compare with flight-derived performance data to validate the use of CFD for the SAVE program. Finally, an extension of the hybrid CFD method and initial results for a 3-airplane echelon formation to highlight the multiple wake interaction effects and complex flow physics is presented.