Characterization of SaOB actuators interacting with flat plate boundary layers

This paper presents results from experiments and simulations of suction and oscillatory blowing (SaOB) actuators in flat plate boundary layers. Experiments use single and multiple component hot-wires and 3D particle imaging velocimetry to study the complex unsteady flow interactions of a single actuator and actuator arrays with cross-flow. Key SaOB variables such as suction geometry, suction flow rate, jet momentum, characteristic jet wave length, array synchronization, and actuator spacing are varied and changes in the external boundary layers are measured. System effectiveness is quantified using boundary layer integral parameters; primarily shape factor as an indicator of resistance to separation. Steady suction is shown to increase near wall velocity by bringing the oscillatory blowing jet closer to the surface as well as providing its own flow control effect. The oscillatory jets generate alternating spanwise vorticity patterns while providing streamwise momentum to the boundary layer. Synchronization and characteristic jet length are shown to alter array effectiveness by changing adjacent jet interactions. Large eddy simulation is used to simulate experiments of both actuator internal and external flows. Simulations of an actuator array show good agreement with experiment in some regions, however, jet interactions and the highly 3D flows require a more thorough validation.