Flow Performance Improvement of Fluidic Oscillator Through Variation in Number of Ribs on Coanda Surface

Abstract

Fluidic oscillators with Coanda surfaces experience several problems, including frequency instability, susceptibility to surface roughness, and complex flow separation, all of which have an effect on performance and need careful optimization for increased efficiency. This study numerically investigates the oscillatory jet flow behavior of a fluidic oscillator, a device that generates oscillating fluid jets through internal flow dynamics. An integral part, the Coanda surface in the mixing chamber, governs internal flow behavior by facilitating attachment and redirection. Key performance parameters, including pressure drop, jet oscillation frequency, and deflection angles, are significantly dependent on the Coanda surface geometry. The study investigates the effect of varying the number of ribs on the Coanda surface, ranging from 1 to 6. Results reveal that the highest oscillation frequency of 875 Hz was achieved with 4 ribs, compared to 355 Hz in the smooth configuration without ribs, whereas the addition of ribs reduces the deflection angle from 53.3 deg (smooth case), the angle increases with a higher rib count, and reaching 37.1 deg for 4 ribs. Moreover, the integration of ribs decreases the pressure drop across the oscillator, an effect linked to the ribs' influence on the formation of the separation bubble in the mixing chamber. Notably, the jet performance parameter, represented by the frequency deflection pressure ratio, exhibits an 87.7% improvement in the case 4 ribs oscillator compared to the smooth oscillator case.