The fast and accurate simulation of aircraft wake vortices evolution and safety assessment of wake encounters are important in identifying the hazard zone of wake vortices, reducing wake separation, and increasing the capacity of airports. However, numerical simulation of wake vortices often takes a lot of time due to a large number of grids. In order to reduce the computation time, Solution-Based Dynamic adaptive mesh method is applied to compute the wake vortex evolution using FLUENT. Three cases with different ambient turbulence intensities are carried out with the large eddy simulation (LES) based on adaptive mesh. The numerical result shows that refiner meshes in the region of the vortex core generated by adaptive mesh method can more effectively capture the dynamics of vortices, identify more secondary vortices and reduce the numerical dissipation due to more compact vortex core resolution. Then, the rolling moment of the following aircraft is calculated and the hazard zone is identified for the aircraft pairing of A340 and A320. The results show that the safety of wake encounters has a close relationship with ambient turbulent intensity and development of vortex instability.

A multi-point aerodynamic design method using a conditional diffusion model addresses aerodynamic challenges across speed regimes for flying wing configurations. The model is based on classifier-free guidance and adopts a three-dimensional (3D) airfoil profile design method for a flying wing layout to perform fast design for five wing profiles of a flying wing layout. The differences between the predicted profiles and aerodynamic performance of the method in the high and low speed integrated design states and the intended target are analyzed, and the aerodynamic performance of the flying wing layout before and after the prediction is compared. The results show that the errors of each of the profile parameters predicted by the method and the real profile parameters are within 3%. Furthermore, the aerodynamic performance of the airfoils derived from the inverse design closely matches the real aerodynamic data at each profile station, meeting the requirements of the inverse design methodology. In addition, the lift coefficient of each profile predicted by the given better aerodynamic performance is improved by about 7.78% on average at high speed, and the drag coefficient is reduced by about 9.23% on average at low speed, which is in line with the predetermined performance enhancement target. Replacing original airfoils with optimized designs improves the flying wing's lift-to-drag ratios in both flight conditions, confirming the method's potential for inverse aerodynamic design in multi-operational flying wing configurations.

Dynamic stall, which has a significant effect on the aerodynamic performances of dynamic airfoils, is closely related to the physics of the dynamic stall vortex (DSV). The physics of the DSV on the NACA 0012 airfoil was experimentally studied using unsteady pressure measurements with high time accuracy. The experimental Reynolds number was Re = 1.5 × 10⁶, and the reduced frequency was k = 0.069. The propagation of the unsteady pressure field during the dynamic stall process was analyzed in detail. The motion characteristics of the DSV were examined, including its near-wall development characteristics and near-wall evolution velocity. Moreover, the frequency characteristics of the near-wall DSV were studied using wavelet analysis combined with proper orthogonal decomposition (POD) technology. In addition, the effects of the mean angle of attack (AoA) and the amplitude on the DSV motion and frequency characteristics were examined in detail. The effects of the mean AoA on the near-wall DSV strength and the propagation velocity were linear, while the effects of amplitude were nonlinear. The mean AoA and amplitude had a significant influence on the frequency of the leading-edge vortex (LEV) at the initial stage of the DSV development (x/c = 0.10–0.20). This work allows the DSV physics to be understood more deeply. Graphic abstract

The aerodynamic performances of aircraft change due to the ground effect for flights near the ground. The air cushion generated near the ground will change the development of the aircraft wake vortex. Researchers have compared several different ground boundary conditions with two-dimensional airfoils, while three-dimensional cases have not been studied specifically. In this study, the effects of stationary and moving wall boundary conditions on the aircraft aerodynamic characteristics and wake development were numerically investigated in three dimensions. The results showed that the stationary wall overestimated the viscous effect of the ground, resulting in a reduction of the wingtip vortex (WTV) vorticity magnitude. The difference appeared at $x=7b$ (wingspan of the aircraft) where the secondary vortex was induced by the wingtip and horizontal tail vortex (HTV).

The difference of the aerodynamic influence of two engine models – the Flow Through Nacelle (FTN) and With Powered Nacelle (WPN) – on BWB300 airframe is analyzed by using the 3-D unsteady compressible Reynolds-Averaged Navier-Stokes (RANS) computation. The results indicate that at cruise condition, the engine shape is a primary factor affecting the BWB airframe upper fuselage surface flow, the two engine models exhibit a similar aerodynamic influence on the BWB airframe. However, at takeoff condition, the two engine models’ aerodynamic influence on the airframe is different, because of the air suction caused by the WPN engine model affecting the airframe upper fuselage surface flow obviously. Moreover, at both cruise and takeoff conditions, the tube formed by the engine and airframe shape changes the surface flow under the engine and the air suction caused by the engine power accelerates the surface flow near the engine.