Velocity measurements in the near wake of a ship superstructure

Velocity measurements in a ship airwake are obtained \textit{in situ} aboard a 108 ft naval training vessel. Three-component sonic anemometers are placed at the bow of the ship, for reference wind measurement, and at numerous locations above a flight deck at the stern of the ship. The mean flow structure resembles that of a 3D backward-facing step, with a recirculation region covering much of the forward flight deck, and significant downwash over the remainder of the surface. Reynolds stresses and two-point velocity correlations are presented, and placed in the context of shipborne helicopter operations. The influence of an atmospheric boundary layer, often unavailable in ship airwake measurements from a wind tunnel, is discussed.