Active flow control in an S-shaped duct at Mach 0.4 using sweeping jet actuators

Abstract

An experimental study was conducted on the flow control capability of sweeping jet actuators (SJAs) in an aggressive offset S-shaped duct with an inlet Mach number of 0.4. The SJAs were placed in two different spacing arrangements to suppress flow separation in the duct and flow distortion at the aerodynamic interface plane (AIP). Multiple measurements were taken, including surface oil flow visualization, steady pressure on the wall surface, five-hole probe pressure, and velocity at the AIP. For the baseline case without control, the surface oil flow visualization and pressure measurement results clearly reflected the three-dimensional flow separation characteristics in the duct. In the controlled cases, the streamwise surface pressure coefficient distribution showed that SJAs can effectively suppress the flow separation. At a spacing ratio of 8.13 and an excitation pressure of 250 kPa, the inflection point of the pressure coefficient Cp was completely eliminated. As a result, the absolute pressure recovery at the upper region of the AIP increased by nearly 5%, and the mean value and RMSE of the cross-flow velocity declined by 54.9% and 48.1%, respectively.