DELAY OF AIRFOIL STALL BY PERIODIC EXCITATION

It was recently demonstrated that oscillatory blowing can delay separa tion from a symmetrical airfoil much more effectively than the steady blowing used traditionally for this purpose, Experiments carried out o n different airfoils revealed that this flow depends on many parameter s such as, the location of the blowing slot, the steady and oscillator y momentum coefficients of the jet, the frequency of imposed oscillati ons, and the shape and incidence of the particular airfoil, In airfoil s equipped with slotted flaps, the flow is also dependent on the geome try of the slot and on the Reynolds number In addition to the flap def lection that is considered as a part of the airfoil shape, The increme ntal improvements in single element airfoil characteristics are genera lly insensitive to a change in Reynolds number, provided the latter is sufficiently large, The imposed oscillations do not generate large os cillatory lift nor do they cause a periodic meander of the c.p.