A novel high-efficiency and high-precision momentum source method for distributed ducted fans in aero-propulsion coupling configuration

The distributed ducted fan-wing integration configuration presents a challenging aerodynamic problem due to its complex aerodynamic coupling effects, making accurate and efficient aerodynamic performance predictions difficult. Therefore, this paper proposes a novel momentum source method for the distributed ducted fan, based on the Reynolds-Averaged Navier-Stokes (RANS) equations, which fully accounts for the multi-component aerodynamic-propulsion coupling effects. By simplifying the flow field calculation of the fan's rotor and stator blades, this method significantly improves computational efficiency while accurately capturing the coupling effects of the wing boundary layer viscous effects, intake acceleration effects, and exhaust wake; thereby, providing precise predictions of the aerodynamic performance for the wing, intake, and exhaust. Specifically, in this method, the RANS equations are solved using the Multiple Reference Frame (MRF) approach to obtain a quasi-steady flow field. Then, the three-directional velocity, turbulent kinetic energy, and turbulence eddy dissipation at the fan's front and rear interfaces are extracted and imposed as boundary conditions to the fan-less configuration to simulate the propulsion effects of the ducted fan. In the single ducted fan-wing section coupling configuration test, the flow field information extracted at a 4° angle of attack can accurately predict the aerodynamic performance of the same configuration within a 16° angle of attack range, as well as the aerodynamic performance of different airfoil configurations. Compared with the MRF method, the proposed method shows a relative error in lift coefficient of less than 2% and in drag coefficient of less than 4.5% in the 2°-16° angle of attack range, demonstrating superior accuracy over traditional momentum source methods while reducing computational cost by more than 90%. In the distributed ducted fan-wing coupling configuration test, this method also demonstrates high accuracy and significant efficiency advantages, providing an efficient and reliable tool for aerodynamic performance prediction of distributed ducted fan configurations.