Steady and Unsteady Control of Nacelle Inlet Flow in Crosswind

The inlet flow of an engine nacelle model is investigated experimentally in the presence of cross flow that induces a complex, azimuthal separation pattern over the inner surface of the inlet’s windward side. The evolution of the separation topology and its receptivity to flow control strategies are investigated in a state-of-the-art crosswind wind tunnel. Three fluidic-based control approaches are considered using steady jets and fluidically-oscillating jet actuators with and without internal feedback. Each of these approaches is tested using the same flow control configuration over a range of flow control parameters, inlet mass flow rates and cross flow speeds. While each actuation approach effects significant improvements over the base flow, the unsteady actuation methods generally outperform the steady method for the same actuation flow rate. Furthermore, it is found that fluidic oscillators are more effective at low speeds in the presence of internal feedback and at high speeds in the absence of internal feedback. Fluidic actuation in the absence of internal feedback reduces the distortion measure IDCmax by 55 and 50% at cross flow speeds of 30 and 35 kts, respectively, utilizing actuation mass flow rates that are lower than 0.3% of the inlet mass flow rate.