A coupled numerical/experimental study of flow separation suppression over a curved surface using fluidic oscillators

Abstract

Fluidic oscillators, devices that generate sweeping jets when supplied with a pressurized fluid, have been used in a variety of flow control applications. The present investigations focus on understanding the physics and numerical prediction of these devices to control separation over a curved surface appropriate for rotorcraft applications. High-fidelity simulations and experimental data are employed to identify the mechanisms responsible for the control of separation. The model design includes an overhang at the interface between the actuators and the outer flow. At this interface, small scale spanwise vortices are shed in the streamwise direction, thereby enhancing wall-normal mixing. The spatial evolution of the sweeping jets give rise to large-scale structures between them causing spanwise mixing. In the mean sense, the jets lead to the formation of recirculation regions near the actuator exits inducing a deflection of the outer flow towards the wall. The simulations also examine the effects of fully resolving the interior of the oscillators, or using a boundary condition model, including turbulence. This boundary condition was found to be able to reproduce the correct physics of the flow control application, including mixing of the sweeping jets with the outer flow.