Ground Effect of a Rotor Hovering above a Confined Area

In this study, an experimental investigation into the effects of confined area geometry on the aerodynamic performance of a hovering rotor was performed from the standpoint of flight safety. The confined area was simulated by vertically placing a single plate or a pair of parallel plates on the ground effect plate. The aerodynamic performance of the rotor changes because part of the rotor wake flowing upward along the walls interferes with the flow field around the rotor. It is shown that the behavior of the steady torque and vibratory thrust coefficients of the rotor significantly depend on the combinations of the distance between the walls, the wall height, and the rotor height from the ground plate. The required torque coefficient at all in-ground-effect rotor heights in the presence of walls is higher than that without walls. For a rotor hovering above the ground with two walls placed asymmetrically, the steady torque and vibratory thrust coefficients are significantly influenced by the wall closer to the rotor. The vibratory thrust coefficient of a rotor above the ground with a wall is larger than that above the ground with asymmetrical walls.