Downwash Wake Reduction Investigation for Application on the V-22 “Osprey” 2003-01-3020
The downwash of the prop-rotor blades of the Bell/Boeing V-22 “Osprey” in hover mode creates an undesirable negative lift on the wing of the aircraft. This downforce can be reduced through a number of methods. Neglecting all other effects, such as power requirements, this research investigated the feasibility of using circulation control, through blowing slots on the leading and trailing edge of the airfoil to reduce the wake profile under the wing.
A model was built at West Virginia University (WVU) and tested in a Closed Loop Wind Tunnel. The airfoil was placed normal to the airflow using the tunnel air to simulate the vertical component of the downwash experienced in hover mode. The standard hover mode flap angle of 67 degrees was used throughout the testing covered in this paper.
All of these tests were conducted at a free stream velocity of 59 fps, and the baseline downforce on the model was measured to be 5.45 lbs. The blowing slots were tested at blowing pressures of 5, 10, 15, 20, and 25 psig, and the slots were independently controlled. Testing was conducted with each slot individually and both slots together. At lower blowing pressures the down force was increased, but as the pressure was increased a reduction was observed. From these initial tests active circulation control can be used as a method to reduce the total downforce on the wings of a tilt-rotor aircraft.