Active Control of Inlet Ducts

Active flow control, via steady control jets, was implemented to improve the performance of a very aggressive (length to exit diameter ratio, L/D, of 1.5) inlet duct. The experiments were performed for a range of inlet Mach number from 0.2 to 0.45. A brand new facility was designed and built to enable various actuation methodologies as well as multiple measurement techniques. In the present work, a pair of steady control jets was placed in streamwise locations where flow was expected to separate. Static pressure measurements, along the upper and lower walls of the duct, were performed for various combinations of actuation. The forcing level of the control jets as well as combinations of jets, were tested. In addition, total pressure measurements were conducted at the Aerodynamic Interface Plane (AIP) to obtain the distribution of the pressure recovery. Flow control was shown to have a substantial effect, mainly on the lower wall. It was found to be more effective at the lower Mach number where the blowing ratio was higher (for the same mass flux ratio). The data suggest that using 2-D flow control to affect a flow field that is highly three-dimensional is not optimal, and as such a spanwise varying actuation should be implemented.