Ducted fans installed on vertical takeoff and landing vehicles experience significant ground effect during takeoff and landing. The aerodynamic characteristics of a ducted fan hovering and transitioning in the ground effect are studied using numerical simulations in this paper. The flowfields are obtained by solving Reynolds Averaged Navier–Stokes equations with the Multiple Reference Frame approach. When a ducted fan hovers in the ground effect, the blade thrust increases due to the combined effect of the increase in the effective angle of attack of the blade and the increase in ambient pressure; the duct thrust decreases due to the combined effect of the decrease in the effective angle of attack of the duct and the increase in ambient pressure. Stall occurs at a certain advance ratio and angle of attack when transitioning in the ground effect. The ground effect delays the occurrence of stall at some advance ratios. The ground effect is hardly detectable at angles of attack less than 30° even if the height drops to 0.5 times the duct exit diameter. At this height and high angles of attack, the different positions and influence regions of the ground vortex at different advance ratios contribute to the different variation trends in the ducted fan performance.

The aerodynamic performances and control characteristics of vertical takeoff and landing aircraft will be significantly affected by the ground effect during takeoff and landing. The longitudinal aerodynamic characteristics and main flow features of a fixed-wing vertical takeoff and landing aircraft hovering in ground effect are investigated in this paper, using Multiple Reference Frame based numerical simulations. The aircraft is propelled by three ducted fans. Results show that the overall morphology of the flow is characterized by a fountain, ground vortex, reingestion, and recirculation. When the thrust distribution between the front and aft ducted fans changes, the flow features change as well. As the aircraft approaches the ground, the ducted fan thrust decreases, the fuselage lift increases, and the total lift first decreases and then increases. The maximum lift increases by 9.6% and the minimum lift decreases by 3.0% compared with that out-of-ground effect. The magnitude of the drag is about 1% of the lift, which has little influence on the aircraft’s performance. The pitching moment gradually changes from the equilibrium state to a significant nose-up moment. The total power consumed increases at a specific rotational speed.

In this paper, the authors describe a software they have developed for wing–body parametric modeling and high-lift system design. This software has the following features: (1) it generates and modifies geometric as well as aerodynamic analysis in the conceptual and preliminary aircraft design phases; (2) it integrates high-fidelity computer-aided design (CAD) and computational fluid dynamics (CFD) software by a graphical user interface(GUI); and (3) it has an aerodynamic/mechanical integrated design and kinematic simulation for a three-dimensional (3D) high-lift device. Based on the application program interface (API) techniques of specialized third-party software, the software integrates B-spline fitting and modeling of airfoil and complex curves, modeling of the fuselage and wings, a high-lift system design, the automatic generation of a structured grid, and high-fidelity CFD code based on Reynolds-averaged Navier–Stokes (RANS) equations. First, the geometry of the fuselage and wing is parametrically generated by lofting with control curves, and then the initial graphics exchange specification (IGES) format geometry is exported to an automatic grid generation module. Finally, the structured grid file is exported to the CFD solver for aerodynamic analysis. The NACA0012 airfoil and DLR-F6 FX2B wing–body model that was published at a workshop are selected for software validation. The cruise configuration model (with nacelle, wingtip, and empennage designed manually) of a 150 seat airliner designed using this software was subsequently used for a high-lift aerodynamic/mechanical integrated design and kinematic simulation. The results illustrate that the software was able to integrate wing–body modeling and high-lift aerodynamic/mechanism design in the conceptual and preliminary aircraft design phases.

The transonic buffet over large aircraft wings seriously affects flight safety and ride comfort; hence, improving transonic buffet characteristics by active or passive control methods has been the focus issue of international researchers. Current research shows that shock control bump (SCB) can decrease shock strength effectively at design conditions and improve buffet characteristics by eliminating shock-foot separation. However, SCB will enhance shock strength or produce a secondary shock at off-design conditions. This paper reveals that when the bump was mounted behind the shock position on the upper wing, it can delay the shock-foot separation merged with trailing edge separation in a wide range of free-stream Mach numbers and improve buffet characteristics. Based on the discovery, three-dimensional studies on Wing1, which was released during the Third Drag Prediction Workshop, were presented in this paper. A full-span bump was added on Wing1 at the rearward position behind the shock, and then buffet characteristics of the basic wing and the wing with bump were analyzed using Reynolds-averaged Navier–Stokes and unsteady Reynolds-averaged Navier–Stokes methods. The results show that the bump can improve the buffet performance of Wing1 over a wide range of free-stream conditions; however, it may deteriorate the aerodynamic performance at prebuffet conditions and improve the aerodynamic performance near the buffet-onset conditions.