Two forward-flow regimes in actuator nozzles with large-amplitude pulsation

Extensive systematic investigations were made of pulsatile flows in a wide range of frequencies (extending over more than a decimal order) in a small nozzle of simple shape and size representative of actuator nozzles generating hybrid-synthetic jets – i.e. with return flow into the nozzle during a part of the cycle. In a synergetic approach, data from hot-wire anemometer measurements are supported and explained by results of numerical flowfield computations. Several effects not previously mentioned in literature were discovered. Particularly interesting among them is the existence of two different characters of the flowfield inside the nozzle in the forward-flow part of the period. In the transition between them, the initial annular-flow dominated configuration changes at a later stage into central-dominated flow.