Abstract
The previous research indicates a possibility of increasing subsonic 2D airfoil cruise lift coefficient C-L by an order of magnitude from 0.4 to 4 with a flapped coflow jet airfoil modified from CFJ-NACA-6421 airfoil at a reasonable aerodynamic efficiency of 48. This paper is to extend the study to 3D wings formed by the same airfoil at various aspect ratios to understand the performance penalized by induced drag. A high cruise lift coefficient is important for ultra-high altitude flight on Earth and flight in Martian atmosphere to overcome the low atmospheric density. The research is based on validated CFD simulation, which employs a 3D RANS solver with Spalart-Allmaras(SA) turbulence model, a fifth-order WENO scheme for the inviscid fluxes, secondorder central differencing for the viscous terms. As a validation, the numerical simulation achieves a very good agreement with the experiment for a 3D wing formed by NACA6421 airfoil with an aspect ratio of 6. The study investigates the 3D CFJ flapped wing at aspect ratio(AR) of 6, 10 and 20 at a freestream Mach number of 0.17 and Reynolds number of 3.48 x 10(6). For the one with AR of 20, a C-L of 3.76 and a moderate (C-L/C-D)(c) of 10.55 are obtained. This research indicates that cruise flight at an ultra-high lift coefficient with an acceptable aerodynamic efficiency appears to be feasible.