Application of synthetic jet arrays for flow separation control on a circular “hump” model

This research investigates the effectiveness of a spanwise array of synthetic jet actuator (SJA) for the control of boundary layer separation over a circular “hump” model. The influence of geometrical and operational parameters – including actuator position, velocity ratio (i.e., the ratio of the peak exit jet velocity of actuators to the freestream velocity of cross flow, VR) and the actuation waveform – on the flow separation control are investigated using hot-wire anemometry (HWA) and particle image velocimetry (PIV) techniques. The effect of the position of SJA array on flow separation control has been studied experimentally over a considerable length of the hump chord (from the “apex” of the model to near the “trailing edge”) for the first time. The investigation looks in more detail into the mechanisms behind the alleviation of adverse pressure gradient as a key factor controlling the flow separation. The investigation of the effect of VR on the performance of SJAs shows the importance of the momentum injection in the mitigation of the momentum deficiency as another important factor in turbulent boundary layer flow separation. A holistic overview of the control parameters allowed to reveal a considerable change in the separation flow patterns. The results show that the best performance of SJA array from the viewpoint of separation control occurs at the velocity ratio of 1.85 with a reduction of the length of recirculation region of around 42.6 and 44.2% by using sine and square waves excitation of SJAs, respectively.