Characterization of periodic flow structure in a small-scale feedback fluidic oscillator under low-Reynolds-number water flow

• Presented numerical simulations and PIV measurements in a fluidics with feedback.
• Detected non-constant Strouhal number/non-linear frequency characteristics.
• Determined feedback flowrate fluctuations through feedback channels.
• Discussed mechanism of jet oscillation in oscillation chamber.

Numerical simulation and experimentation using high time-resolved particle imaging velocimetry were conducted in order to clarify the flow characteristics in a small-scale feedback fluidic oscillator operated under low-Reynolds-number water flow. Flow oscillations were triggered by the Coanda effect and a periodically oscillating jet. Based on spectral analysis of the velocity fluctuations inside the oscillator body, the Strouhal number was not constant and the frequency was not linear with respect to the flow rate for the Reynolds number range from 238 to 714. The flow rate fluctuations of the feedback flows through the two feedback channels were determined quantitatively. By comparing the simulation and experimental results, the mechanism of the small-scale feedback fluidic oscillator was clarified by considering the time for a jet to oscillate from the center of the control region to either of the attachment walls and the time for a jet to oscillate from either of the attachment walls to the center of the control region separately.