Comparison Between Fluidic Oscillators and Steady Jets for Separation Control

An experimental study was conducted to compare performance and efficiency between fluidic oscillators and steady jets with respect to commonly used flow control coefficients for momentum, mass flow, and energy in support of the development of active flow control technology. Different actuation modules were tested on a model of the NASA hump geometry. Time-averaged pressure measurements were conducted with high spatial resolution, and stereoscopic particle image velocimetry was performed downstream of the actuation location to investigate the performance differences in detail. Surface flow visualization in a quiescent environment was employed to assess the spreading angle of the various actuators. Results show that fluidic oscillators are almost always superior to steady jets with respect to any flow control coefficient at a given spacing. The lone outlier occurs for tightly spaced actuators in which both perform similarly with respect to the energy coefficient. This general superiority is in part due to a larger jet spreading angle, the associated spanwise coverage, and the existence of stronger coherent streamwise vortices in comparison to steady jets.