Flow physics of drag reduction mechanism using suction and pulsed blowing

An active flow control (AFC) study using steady suction and oscillatory blowing (SaOB) actuators was conducted on an axisymmetric bluff body model for a range of Reynolds numbers between 2 × 10⁶ and 5 × 10⁶. This paper is a continuation of a previous paper which demonstrated the experimental implementation and efficient drag reduction of the SaOB actuator system on the axisymmetric model, including comparisons to CFD results. The objective of the current paper is continued analysis of the experimental data coupled with further refined computational model toward a flow physics understanding of the drag reduction mechanism of the SaOB flow control system. The boundary layer response was examined using time-averaged and phase-averaged hot-wire measurements conducted on the aft portion of the model. The drag reduction behavior was scaled using multiple AFC parameters associated with the unique features of the SaOB actuators. Results show that the drag reduction mechanisms associated with the SaOB actuation system include boundary layer suction, wall-jet momentum addition, unsteady shear layer excitation, thrust, and streamwise vortices.