Delayed Detached Eddy Simulation of Flow Separation Control Using Fluidic Oscillator

Abstract

The investigation of flow separation control over a NACA 0015 airfoil model using a fluidic oscillator (FO) is conducted through delayed detached eddy simulation. First, the flowfield within and outside an FO operating in quiescent air is resolved simultaneously. The oscillation of the jet flow induced by the FO is attributed to the cyclic expansion and contraction of the recirculation bubbles located near the two Coanda surfaces in the mixing chamber. Significantly, the predicted jet oscillation frequency closely matches the experimental data, validating the accuracy of our findings. Next, the FO is integrated into an airfoil model to suppress the flow separation. The airfoil is under deep stall conditions, with angles of attack of 20 and 17° and a Reynolds number of Re=4.8×105. The key driving force for flow reattachment is the spanwise vortices induced by the oscillating jet, which substantially enhance the mixing between the separated flow and the external high-momentum flow. Consequently, the aerodynamic performance of the airfoil is notably improved. Additionally, both spectral and dynamic mode decomposition analyses indicate that the flow, under the influence of the FO forcing, becomes more orderly and well-organized and is effectively locked into the forcing frequency.