Steady Versus Unsteady Pneumatic Flow Control and Aspects of Practical Integration

A systematic study that compares the performance of flow control using steady and unsteady actuation is presented. A family of convergent–divergent nozzles is derived from the fluidic oscillator actuators developed at NASA to produce a set of constant-blowing actuators. The performance of the steady-blowing actuators is compared with that of the original fluidic oscillator using computational fluid dynamics. The flow control characteristics are first established for the actuators in a bench-test setting. Aerodynamic applications for a set of airplane configurations and flight objectives are then used to evaluate the relative flow control performance of the various actuators at realistic flight conditions using consistent actuator layouts. In some cases, where space availability is the prime determinant of system integration, the only viable flow control solution for achieving design targets is provided by constant-blowing actuators. Wind tunnel assessment is also performed for steady and unsteady actuators embedded in a high-lift wind-tunnel model. As the aviation industry seeks to develop the framework for optimal integration of flow control technology into flight vehicles, the study also addresses issues of practical airplane implementations in view of the underlying differences between the steady and unsteady modes of pneumatic actuation.