Effects of Wing Aspect Ratio on Mutational Ground Effect Aerodynamic Characteristics

The existing literature on mutational ground effect (MGE) shows that airfoils and small-aspect-ratio delta wings exhibit different lift variation patterns during landing on an aircraft carrier deck. To understand the flow physics behind the aforementioned differences, the effects of aspect ratio (AR) on the aerodynamic characteristics of a rectangular wing in MGE are investigated using unsteady RANS simulations. In the chord-dominated MGE, the aerodynamic forces of an airfoil exhibit violent oscillation phenomena, which are attributed to the appearance and disappearance of platform obstruction and upwash flow during the process of approaching and entering the platform. In the span-dominated MGE, as the AR decreases, the oscillation magnitude of the aerodynamic forces gradually decreases until it disappears. When the wing approaches the platform, a portion of the induced flow beneath the wing is diverted into spanwise flow, leading to a weakening of the platform obstruction effect and upwash flow. The wingtip vortex transitions from the unbounded flow regime to the static-ground-effect mode: the transition proceeds monotonically and smoothly in the spanwise direction, while it exhibits oscillatory characteristics in the vertical direction due to the oscillating upwash flow around the platform sidewall.