On the modelling of the switching mechanisms of a Coanda fluidic oscillator

International audienceA Coanda fluidic oscillator has been studied numerically and experimentally to understand the internal switching mechanism and to estimate the frequency of resulting pulsed jets. 2D numerical simulations were performed and the oscillator switching mechanism was unveiled. The results of the simulation confirmed that the pressure difference between the two control ports and the pressure difference between the two branches control the oscillation dynamics of the oscillator. A detailed function defining the pulsation frequency has been proposed, taking into account the forth and back velocities of the pressure wave in the feedback loops which are difficult to measure experimentally. A simplified form of the frequency function has thus been proposed. An experimental study was performed to validate the numerical results, using two oscillator prototypes having the same central part but different feedback loop configurations. The experimental results confirmed the frequency function proposed from the computational study. The effects of the inlet pressure and the length of feedback loops have been experimentally studied. It has been found that with a given feedback loop, the oscillation period initially decreases as the input pressure increases