## 5 Results
### Modifying the (Mc) Outlet Angle
On the other hand, whenever the output angle increases, Figure 11a, the jet leaving the (MC), tends to run tangential to the (MC) converging walls, therefore directing a smaller amount of fluid through the feedback channels, and even more important, the formation of a high pressure stagnation point is reduced to a very small converging walls section, its peak to peak amplitude and maximum value are also minimized, see Figures 11c and 12c. As a result the time needed for the main jet to flip over increases, and accordingly the oscillation frequency decreases. It is also interesting to realize that at the external chamber (EC), a large vortex is generated at the opposite exit from the one the flow is leaving the amplifier. In fact the vortex covers the entire opposite exit, preventing flow from outside the (FO) to enter into the (EC). This vortex intensity was observed to be slightly higher as the angle decreased. For the smallest (MC) outlet angle, the turning speed associated to this particular vortex was of 117 rad/s, while when highest outlet angle is used, the turning speed was of 67 rad/s. Figure 11: Fluidic oscillator internal velocity field (**a,b**) and pressure magnitude (**c,d**). Maximum outlet angle (**a,c**), minimum outlet angle (**b,d**). Reynolds number 16034. The effects on the (FO) outlet mass flow, the (FC) mass flow, the net momentum acting on the (FC) outlets, the stagnation pressure on the (MC) converging walls, and the (MC) jet oscillation angle, for the baseline case, the lowest and highest mixing chamber outlet angles evaluated, at Reynolds number 16034, are presented in Figure 12. The first thing to observe is that the (MC) outlet angle modification, generates a clear effect on the (FO) main parameters. As the outlet angle increases, a clear peak to peak amplitude reduction of all measured parameters was observed. For the (MC) smallest outlet angle studied, the mass flow frequency and amplitude at the (FO) outlet are maximum, the reverse flow is also the largest. The peak to peak mass flow amplitude at the (FC's), is about 53% smaller when using the highest (MC) outlet angle than when using the smallest one. Under all (MC) outlet angles studied, the (FC) mass flow always goes from the (FC) inlets to outlets, for the lowest outlet angle, the minimum (FC) mass flow is about zero, see Figure 12e. The average pressure at the (MC) lower converging wall, is around 22% lower for the highest (MC) outlet angle than for the lowest one. When the lowest (MC) outlet angle was employed, a clear difference between the static pressure at the (FC) outlets was observed, a maximum pressure difference between both outlets of over 3000 Pa was measured. For the lowest (MC) outlet angle, the net momentum acting onto the lateral sides of the main jet entering the (MC), is about 38% higher than when the highest angle is used, Figure 12d. This effect helps in generating a much larger jet oscillation amplitude in the (MC) and at the (FO) outlet mass flow, see Figure 12a,b. The conclusion is that high oscillation amplitudes are linked with high pressure variations on the (MC) converging walls and therefore on the (FC) outlets.