The Influence of Location of Coanda Surface Ribs on Fluidic Oscillator Performance

Double feedback fluidic oscillators, which create oscillating fluid jets, are commonly used in flow control and thermal applications.The geometry of the Coanda surface affects the oscillation frequency, jet deflection angle, and pressure drop in the mixing chamber.This study numerically investigates the impact of rib locations on the Coanda surface on jet characteristics.Air, with an inlet velocity of 55.8 m/s, is used as the working fluid.Three cases-full ribs, upper ribs, and lower ribs-are compared to a smooth Coanda surface.The full ribs case achieves an increased oscillation frequency of 820 Hz, compared to 355 Hz for the smooth case.However, the jet deflection angles decrease when ribs are present.The upper ribs case achieves a larger 41.5 deflection angle, while the full ribs case achieves a relatively lower 33.8 angle.Interestingly, adding ribs to the Coanda surface reduces the pressure drop in the oscillator.Oscillators with upper ribs achieve a 76.1% increase in FDPR compared to smooth cases, making them the best solution for enhancing the combined effect of jet oscillation frequency and deflection angle.