Enhancing fluidic oscillator performance using multiple backward-facing steps in the mixing chamber

Abstract The increase in FO frequency due to the use of BFS is accompanied by an increase in pressure losses. The study was conducted using the URANS governing equation and the SST k-ω turbulence model. Double BFS exhibited the highest frequency, with an average increase of 25.78% over the prototype. In contrast, the average frequency increases of single and triple BFS were 20.29% and 19.6%, respectively. The frequency increase is influenced by the momentum of the backflow in the feedback channel. Double BFS had a lower pressure loss than the prototype model, with 4.54% reduction. The average pressure loss of the single BFS model was 24.9% higher than that of the prototype model, whereas the triple BFS model showed a 0.039% increase. The pressure loss is influenced by the recirculation bubble in the FO chamber. Nondimensional analysis using Strouhal and Euler numbers also showed that double BFS exhibited the best performance. The prototype model and single BFS had a velocity profile shape that is closer to a homogeneous shape. The double and triple BFS exhibited a velocity profile shape that is closer to the bifurcated jet shape. Bifurcated jets, which exhibit a wider spread, are characteristic of oscillatory flows. Thus, it can be concluded that the double BFS FO is more recommended.