Numerical Investigation of Tandem Flapped Coflow Jet Wings at Cruise at Low Reynolds Numbers

This study numerically investigates the aerodynamic performance of 3D tandem Flapped CoFlow Jet (FCFJ) wing configurations designed for high lift cruise operations under low Reynolds number conditions representative of the Martian atmosphere. The tandem FCFJ wing system integrates fore and hind FCFJ wings equipped with deflectable flaps, enabling substantial flow turning capabilities to achieve ultra-high cruise lift coefficients while maintaining reasonable aerodynamic efficiency. Optimizing the tandem wing geometric arrangement and investigating wake interference mitigation strategies represent the primary objectives of this research. The study employs an in-house validated 3D Reynolds Averaged Navier-Stokes (RANS) solver with the Spalart-Allmaras (SA) turbulence model, a third-order WENO scheme for inviscid flux calculations, and second-order central differencing for viscous terms in CFD simulations. The comparative analysis reveals that while tandem configurations experience wake interference effects reducing hind wing performance by approximately 7.5%, the system achieves nearly 1.9-fold increase in total lift generation compared to single wing arrangements due to increased wing area. The aerodynamic performance degradation caused by tip vortex in 3D configurations is effectively mitigated by incorporating circular tip caps, providing 6.5% improvement in lift-to-drag ratio. The geometric parametric study demonstrates that FCFJ wings with β = 35 deflection fundamentally alters wake interaction mechanisms, resulting in minimal sensitivity to stagger distance and vertical gap variations. Furthermore, aspect ratio study reveals a good balance when the fore wing operates at AR 3.33, achieving maximum system corrected aerodynamic efficiency of 6.32. Scaling studies confirm the technology’s robustness across different vehicle sizes, maintaining strong performance despite at low Reynolds number. The tandem FCFJ system demonstrates exceptional capability for achieving cruise lift coefficients exceeding 3.4 with corrected aerodynamic efficiency CL/CDc of 6.32 and CL/CD of 10.88, suitable for Mars atmospheric conditions, establishing a foundation for compact, high-performance aircraft designed for Mars exploration missions.