Feasibility analysis of fixed plates in chord-dominated dynamic ground effect wind tunnel experiment

Abstract

The dynamic ground effect (DGE) refers to the take-off and landing process where the distance between airplane and ground constantly changes with time. In the wind tunnel experiment of DGE, fixed plates are often adopted to substitute the moving-belt ground, which will affect experimental reliability. In this paper, the landing process of an airfoil is simulated to study the feasibility of fixed plates in the chord-dominated DGE experiment. The height is divided into two regions based on the aerodynamics and flow patterns. In Region I (large height), DGE is dominated by the static ground effect (SGE), using a fixed plate can effectively balance the camber effect, blocking effect and boundary layer effect to reproduce result of the moving-ground condition. In Region II (small height), DGE is dominated by the compression work effect, where the downwash is highly compressed to diverge into a forward stream and a backward stream. When using fixed plates, the downwash exhibits two kinds of escaping behavior: the leading-edge-preferred escaping behavior for most fixed plates due to thick boundary layer and the trailing-edge-preferred escaping behavior for the very short plate due to the suddenly weakened camber effect. No plate can balance the two kinds of flow to accurately reproduce pressure distribution on airfoil lower surface and flow physics of moving-ground condition. Thus, the use of a fixed plate is infeasible.