Improvement of Helicopter Operations on Frigates Using the Coanda Effect

The flow surrounding a frigate is characterized by high-velocity gradients and flow detachment behind the superstructure of the ship. Therefore, the helicopter pilot’s workload during the recovery maneuvers above the flight deck can increase. Different techniques of flow control have been tested for reducing the flow detachment and pilot workload. In this paper, a combined numerical optimization and experimental tests in a wind tunnel are performed to analyze the implementation of the Coanda effect at the back part of the hangar as an active flow control technique to reduce the flow detachment above the flight deck. The numerical optimization is conducted by testing different velocities and geometries of the Coanda hangars tested. The best results show a complete elimination of the flow detachment above the flight deck and an up to 2.85 times reduction of the low-speed area with respect to the base case. The geometries selected from the numerical results were installed in a scaled simple frigate shape 2 (SFS2) and tested in a wind tunnel with particle image velocimetry (PIV). The experimental results also show a drastic reduction of the flow detachment above the flight deck combined with reduced levels of turbulence intensity at the height where the helicopter rotor must operate during the recovery maneuver.