A fluidic oscillator capable of switching between steady and unsteady jet modes

Conventional fixed-geometry fluidic oscillators exhibit limited effectiveness under diverse flow separation conditions. To address this limitation, we propose a fluidic oscillator capable of transitioning between steady and unsteady jet modes. This design enhances adaptability, improving flow control across varying external flow fields. Specifically, the oscillator features a flexible membrane adhered to the inner wall of its mixing chamber, creating a static pressure chamber. By active or passive deformation, the flexible membrane can switch between different modes, generating either sweeping or steady jets. Numerical simulations are conducted to evaluate the performance of the oscillator, with a focus on its flow loss characteristics, jet frequency, and sweeping angle amplitude. In this study, a nondimensional index Rm was defined to quantify the distance between the flexible membranes, and simulations of the models with typical deformed mixing chamber walls are conducted. It is revealed that for the prototype oscillator (i.e., Rm=1), the primary flow characteristics exhibit low-frequency, high-amplitude oscillations, accompanied by substantial pressure losses. However, as Rm decreases, the total pressure loss in the oscillator diminishes, the jet frequency increases, and the jet sweeping angle amplitude gradually decreases. Notably, when Rm is reduced to 0.23, the total pressure loss coefficient of the fluidic oscillator decreases by 45.2% compared with that of the prototype, and the flow at the oscillator outlet approximates a steady jet. Therefore, by enabling jet mode switching, this novel fluidic oscillator expands the range of applications for fluidic oscillators in flow control and significantly improves their performance under diverse operational conditions.