Download Alleviation on a V-22 Model Having a Simple Flap Used in Conjunction With Periodic Excitation, Suction and Blowing

Download measurements were carried out on a V-22 airfoil whose Fowler flap and the associated flap follower were replaced by a simple flap. Steady and periodic suction and blowing as well as purely periodic excitation were applied to the flap in order to alleviate the download. The dependence of the download alleviation on flap's slot location, the method of actuation, the level of momentum input and the frequency of the periodic actuation were investigated. Steady blowing at low momentum coefficients proved to be ineffective. The possible ramifications of adding a flat Kruger flap were also considered. Based on this data the download alleviation was measured on a three-dimensional, 1/10^th scale model of the airplane whereupon the parametric studies carried out in two dimensions were confirmed. The use of suction in conjunction with a Kruger flap reduced the download on the model by 38% while weak periodic excitation in the absence of a Kruger flap reduced it by 16%.