## 5 Results
### Modifying (Mc) Outlet Width
Regardless of the outlet width, a vortex at the external chamber upper side, can be spotted, yet its intensity and turning speed associated are much smaller for the highest than for the lowest outlet widths studied. The turning speed of this particular vortex for the lowest and highest outlet widths studied, was respectively of 301 and 59 rad/s, which explains why the pressure at the (EC) is particularly low at small outlet widths. Figure 8: Fluidic oscillator internal velocity field (**a**,**b**) and pressure magnitude (**c**,**d**). Maximum outlet width (**a**,**c**), minimum outlet width (**b**,**d**). Reynolds number 16034. The same dynamic parameters evaluated in the previous section and introduced in Figure 5, are now being presented in Figure 9 for the maximum, minimum and baseline (MC) outlet widths studied. When the highest (MC) outlet width is employed, the (FO) outlet mass flow amplitude is minimum, there is no reverse flow at any time. As the (MC) outlet width decreases, the reverse flow at the (FO) outlets keeps increasing, consequently the (FO) mass flow amplitude increases, see Figure 9a. Another relevant effect associated to the decrease of the outlet width, is the progressive increase of the (MC) pressure, notice that the average value of the stagnation pressure fluctuations presented in Figure 9c, increases around 19 times when comparing the maximum and minimum outlet width values. For the lowest outlet width evaluated, the stagnation pressure fluctuations at the (MC) lower converging wall, show a quasi-chaotic behaviour, probably due to the stagnation pressure points appearing simultaneously on both (MC) converging walls, see Figures 8d and 9c, although clear oscillation signs are still to be seen. Under these conditions, the curve representing the net momentum is particularly scattered. This fact is clearly understood when considering that the main term of the net momentum is the pressure term, as observed in Figure 6 for the previous case. Regarding the net momentum responsible of the jet fluctuations inside the (MC), see Figure 9d, its amplitude is about 38% smaller for high outlet widths than for the smaller ones. Notice as well that for the highest outlet width, the stagnation pressure peak to peak amplitude is about 40% smaller than for the smallest outlet width evaluated. These values suggest a direct relation between the stagnation pressure peak to peak amplitude and the net momentum driving the jet oscillations. Another point to be discussed may be, why the net momentum shows rather a sinusoidal curve when the stagnation pressure oscillations, specially at the lowest outlet width, looks rather chaotic. The reason is the integration effect the (FC's) outlets are having on the pressure oscillations. The study of the (MC) incoming jet oscillation angle, see Figure 9b, shows that the smallest oscillation amplitude appears when the highest outlet width is employed. The maximum jet oscillation angle amplitude, obtained for the minimum outlet width, is about 3% higher than the one generated for the baseline case, and about 29% higher than the one obtained when using the maximum outlet width. From Figure 9, a direct correlation between the peak to peak stagnation pressure, the (MC) inlet angle amplitude, the (FO) output and (FC) mass flows amplitude, as well as the net momentum amplitude, appears to exist. Small stagnation pressure amplitudes generates small amplitudes in all these parameters. When evaluating the feedback channel mass flow, Figure 9e, regardless of the outlet width, it is observed there is an average mass flow flowing from both feedback channel inlets to the outlets. Its average value remains pretty much constant regardless of the outlet width chosen, although it was observed it increased with the Reynolds number increase. For the smallest (MC) outlet width evaluated, just a very small reverse mass flow exists on both feedback channel outlets, the reverse flow increases with the Reynolds number increase.