## 5 Results
### Modifying the (Mc) Inlet Width
The origin of the pressure waves, responsible of the (FC's) periodic pressurization, are the stagnation pressure points appearing alternatively at the (MC) outlet converging walls, see the red spots observed in Figure 4c,d. At small inlet widths, Figure 4b,d, the (MC) incoming jet impinges alternatively at the (FC's) outlet internal vertical walls, generating an stagnation pressure point from which pressure waves are being sent alternatively from both (FC) outlets to the inlets, see the small red spot observed at the upper feedback channel outlet, Figure 4d. Reverse flow, from (FC) outlets to inlets is therefore generated, although for this particular case, the oscillation still exists. This is because the stagnation pressure at the (MC) converging walls, is acting over a surface about 20 times bigger than the one affected by the pressure at the (FC's) outlet internal vertical walls, and despite the fact the maximum pressure at the (MC) outlet converging walls, is for the present case, about 22% smaller than the maximum pressure existing at the (FC's) outlet internal walls, the time the stagnation pressure is acting on the (MC) converging walls, is 6.4 times longer than the time the stagnation pressure point appears at the (FC) outlet internal vertical walls, being this time difference along with the area the stagnation pressure acts, what maintains the oscillation. Although no figure related is presented in the present manuscript, if the inlet width would be further reduced, the stagnation pressure points at the (FC's) outlet vertical walls, would be appearing simultaneously on both vertical walls, generating reverse flow on both sides of the external chamber and the pressure distribution. Figure 4: Fluidic oscillator internal velocity field (**a,b**), and pressure magnitude (**c,d**). Maximum inlet width (**a,c**), minimum inlet width (**b,d**). Reynolds number 16034.  
feedback channels at the same time. Pressure waves would also be continuously transfered from the (FC's) upstream to downstream. Under these particular conditions oscillation would stop. The evaluation of the dynamic values of the, net-momentum acting onto the jet entering the mixing chamber, the pressure at the (MC) outlet converging walls, the (MC) inlet inclination angle, the (FC's) mass flow and the (FO) output flow, greatly helps in understanding the (FO) dynamic performance. Figure 5 introduces the non-dimensional dynamic values of the mass flow through one of the (FO) outlets, the lower (FC) mass flow, the stagnation pressure at the (MC) outlet lower convergent wall, the net-momentum acting on the (MC) incoming jet and the (MC) inlet jet inclination angle. The Reynolds number was kept constant at 16,034. In each graph it is presented the non-dimensional dynamic value obtained for the baseline case, original actuator, and the corresponding ones characterizing the maximum and minimum inlet widths evaluated at which pulsating flow was observed. The first thing to notice is, that the dynamic stagnation pressure appearing alternatively at the (MC) converging walls, Figure 5c, is driving the oscillation, the rest of the graphs presented simply follow these pressure pulsations. From the oscillator upper outlet mass flow graph, Figure 5a, it is observed that the mass flow amplitude is directly linked with the reverse flow appearing at the (FO) outlets, the higher the reverse flow the higher the mass flow outlet amplitude, large reverse flows are associated to small inlet widths. This direct relationship is obvious when considering that the incoming (FO) mass flow is constant and given by the inlet boundary conditions, and at each instant, the mass flow through the two (FO) outlets must be the same as the inlet mass flow, the fluid is considered as incompressible. Therefore, if at some particular time, reverse flow appears at one of the (FO) outlets, the (FO) mass flow amplitude must increase to fulfill the continuity equation at each time instant.