Study of Passive Flow Control for Ship Air Wakes

Abstract

Abstract : This Trident project expands ongoing ship air wake research being conducted at the United States Naval Academy (USNA). The objective of this project is to examine the effects of passive flow control techniques aimed at reducing the impact of ship air wakes on naval rotary wing aircraft flight operations. Helicopter flight operations on destroyers and cruisers are limited to specific flight envelopes to ensure the safety of the pilot and aircraft. These flight envelopes are developed based upon helicopter operating capabilities and the impact of air wakes on the aircraft. Modifying the size, shape, and turbulent flow structures of a ship air wake could allow for more expansive helicopter flight envelopes. For this Trident project, a solid, notched fence was placed along the top and sides of the YP hangar, angled aft by 30 degrees, and along the starboard flight deck, angled out board by 30 degrees. Air wake data for this configuration was measured with underway in situ testing, computational fluid dynamics (CFD) simulations, and wind tunnel scale model experiments to provide a complete analysis of the effects of the fences on the YP's air wake. This investigation showed that this particular passive flow control fence may produce a less favorable ship air wake for helicopter launch and recovery operations due to an increase in shear, turbulent kinetic energy density, and mixing within the helicopter landing region.