# Novel Fluidic Oscillator Evaluation Considering Dimensional Modifications
## 1 Introduction
In the research performed by [38], supersonic fluidic oscillators to be used in the generation of self-sustained oscillations inside gas-pressurized chambers were investigated. It was realized that 2D-CFD simulations were not able to reproduce the transients as accurately as in three-dimensional simulations. Therefore, and in order to predict the performance of the prototype, a low-order fluid circuit model was generated. In the experimental study performed by [26], six different FC lengths and three FC sections were analyzed; three power nozzles and exit throat sections were also considered. The Coanda effect on the FO's curved- or straight-exit geometries and their relation with the jet oscillation angle were discussed. The aspect ratio (AR) was defined as the relation between the exit throat width and its height, the ratio (MR) between the power nozzle area and the exit nozzle was found to be of particular relevance when evaluating the FO outlet frequency. They obtained an equation relating the outlet frequency with the Reynolds number, and the AR and MR ratios, and it was clarified that these two ratios are the most important when analyzing FOs. In the articles from [4; 5], the performance of FOs with different outlet bending angles was evaluated. It was observed that the outlet frequency increased with the bending angle as well as with the incoming mass flow. These particular FOs were inserted in an NACA 0015 profile and the effects of bending and pitch angles on the profile lift and drag coefficients were evaluated. The lift coefficient increased with the bending angle increase until reaching an optimum value of 35\({}^{\circ}\); the profile efficiency increased with increases in both angles. The effect of using curved FOs was revealed in [39; 40]. In fact, the need for evaluating these configurations arises when trying to implement FOs in turbine blades or airfoil profiles, among other applications. FOs bend with different radii across the cross-stream direction, and flat FOs with just the exit nozzle curved in the same direction were considered by [39]. It was realized that a good out-of-plane motion of the exiting jet and the largest sweeping angle increase was obtained when using the curved exit nozzle configuration. FOs curved along the flow direction were evaluated in [40]. The oscillating frequency increased with the curvature while sweeping decreased. At very high curvature, no sweeping angle was observed. As previously noted by [26], they realized the important effect of the FO's aspect ratio and generated an equation for the Strouhal number, which highlighted the importance of this ratio. A novel shape of FO at very low Reynolds numbers was numerically studied for the first time by [PERSON] et al. [41]. In this paper, it was noted that at a given Reynolds number, \(Re\mathcal{O}10^{2}\), the amplitude of the jet sweeping angle was more pronounced for the two-dimensional fluidic oscillator than for the corresponding three-dimensional one. In the present research, the new configuration formerly analyzed by [41], and lately studied at much larger Reynolds numbers by [42], is further evaluated. In fact, the present numerical study is a continuation of the work performed in [42], where several MC outlet widths and inlet angles were considered. In the present paper, the combination of changing the MC inlet width and its internal angle, as well as the effect of FC dimensional modifications, is presented. The origin of self-sustained oscillations is further clarified, concluding that the present FO configuration is pressure-driven, but the mass flow forces appear to be more relevant than in the former studied configurations [22; 23]. A completely novel equation relating the FO outlet mass flow frequency with the time-averaged FC reverse flow is also presented. Fluid is considered as incompressible and the Reynolds number is kept constant to \(Re=54\),595 across the entire study. The rest of the paper is designed as follows.