# Novel Fluidic Oscillator Evaluation Considering Dimensional Modifications
## 6 Results
### Mixing Chamber Angular Modifications (2D-CFD)  
In the present subsection, the effects of modifying the mixing chamber angle are introduced. To properly understand the following observations, the reader should recall the information presented in Figure 3a and Table 3. Note that all information presented in this subsection was obtained through 2D-CFD simulations. Before presenting the results, it is important to note that the mixing chamber angular modifications in reality slightly modify the feedback channel length, they considerably modify the mixing chamber entrance width, and they also modify the feedback channel outlet width a bit. The largest modification is at the mixing chamber entrance width: for an angle of \(\delta_{1}=\delta_{STD}+15^{\circ}\), the entrance width decreases by 13.7% versus the baseline case; and when the angle is \(\delta_{4}=\delta_{STD}-15^{\circ}\), the  
Figure 8: Instantaneous velocity fields obtained at the respective time at which reverse FC mass flow was maximum. Baseline case. 3D simulations (**a**). 2D simulations (**b**). Figure 7: Comparison between 2D- and 3D-CFD simulations. Fluidic oscillator outlet mass flow (**a**). Stagnation pressure dynamics at the MC’s lower converging wall (**b**). Unsteady pressure at the lower feedback channel outlet (**c**). Lower feedback channel outlet mass flow (**d**). entrance width increase is about 56.8% versus the baseline case. For these two respective angles, the FC length increases and decreases, respectively, by 1.3% and 5.4%. The FC outlet width when \(\delta_{1}=\delta_{STD}+15^{\circ}\) suffers a small decrease of 0.65% versus the standard value, and for \(\delta_{4}=\delta_{STD}-15^{\circ}\) the MC entrance width increases by around 0.77% versus the baseline case. Therefore, what mostly affects the fluidic oscillator dynamic performance is the variation in the mixing chamber entrance width; the other two secondary modifications generate less relevant effects. Figures 9 and 10, respectively, introduce the velocity and pressure fields for the maximum (\(\delta_{1}=\delta_{STD}+15^{\circ}\); entrance 1) and minimum (\(\delta_{4}=\delta_{STD}-15^{\circ}\); entrance 4) studied. In both figures, the oscillation period is divided into four equidistant time steps. The initial time T = 0 is taken as the instant at which the stagnation pressure at the MC's upper converging wall is about its maximum; see Figures 9 and 10, where the jet inside the MC is moving downwards, then the upper FC is pressurized. At this particular instant, a large FC reverse flow is observed for the configuration \(\delta_{1}=\delta_{STD}+15^{\circ}\), Figure 9a, but a considerably smaller reverse flow is seen for the configuration \(\delta_{4}=\delta_{STD}-15^{\circ}\), Figure 10a. In the next time step, T = 1/4 (Figures 9 and 10c,d), the jet inside the MC has reached its lowest position and has started to move upwards, the lower FC is beginning to be pressurized, reaching its maximum pressure at T = 1/2 (Figures 9 and 10f). The maximum reverse flow is now observed at the upper FC, but just for the \(\delta_{1}=\delta_{STD}+15^{\circ}\) configuration, Figure 9e; then, just a minor reverse flow is observed for \(\delta_{4}=\delta_{STD}-15^{\circ}\) (Figure 10e). It is relevant to note the stagnation pressure points appearing alternately at the MC's upper- and lower-wedge left-hand-side vertices, Figure 9b,f, which are created by the jet entering the MC and partly impinging at these vertices. These stagnation pressure points are not observed in Figure 10. Finally, at T = 3/4 the jet inside the MC is already moving downwards due to the upper FC pressure increase generated by the MC jet impinging at the MC's upper converging wall; see the red area in this particular location. A comparison of the vortical structures forming inside the MC and in the FCs of Figures 9 and 10 serves to further understand the differences between these two FO configurations.