Active separation control applied to an axis-symmetric body

An active flow control (AFC) study using steady suction and pulsed blowing in close proximity was conducted on an axis-symmetric bluff body configuration at Reynolds numbers between 1x106 and 5x106 based on the model length. The study was performed in a coupled manner with flow computations being used intensively during the experiment design. Subsequently, experiments and computations were used to optimize steady suction flow control alone. Finally, actuation was provided by a synchronized array of Suction and Oscillatory Blowing (SaOB) actuators. The results show the suction effect alone has a very limited ability to delay separation and reduce drag on the current geometry. Some suction configurations are shown to actually increase drag significantly. The addition of pulsed blowing enables separation delay to the trailing edge of the body and drag to be nullified. A portion of this drag reduction can be attributed to thrust of the pulsed blowing, demonstrated by net thrust at certain conditions. However, increased overall system efficiency, considering also the total invested actuation power, was found only at low momentum input. This was partially attributed to the particular geometry used, as the AFC system shows a robust ability to delay separation from its baseline location to the trailing edge. A detailed parameter study and flow field analysis reveals frequency sensitivity that is in agreement with earlier studies of active separation control. The measured data is a good source for computation validation; towards a tool for design optimization. However, due to the demanding nature of this complex configuration, not all the measured trends were predicted or reproduced by the computational model. This step requires further investigation.