## 5 Results
### Relation Reynolds Frequency for All Dimensional Modifications Performed  
After evaluating the fluidic oscillator output mass flow frequency and amplitude as a function of the different internal modifications and at several Reynolds numbers, one of the conclusions from the present paper is, that the conventional Reynolds-frequency linear behaviour for a given oscillator, can be expressed of a set of linear functions. Each line represents the operating conditions of the fluidic oscillator once a particular modification is undertaken, notice that in almost all cases, a linear relation is obtained, see Figure 16. For example, the increase of the inlet width, and regardless of the Reynolds number employed, generates output frequencies considerably higher than the baseline case. The (FO) outlet mass flow oscillating frequency, increases versus the baseline case one, by around 40% when the maximum inlet width is employed. The outlet frequency also increases when employing the lowest output angle or the lowest output width, although for these particular cases the increase is smaller than 7%. The rest of the internal modifications, generate frequencies slightly smaller than the baseline case ones, the trend is the same for all Reynolds numbers studied. It is also interesting to observe that, when the highest (MC) outlet angle is used, the expected Reynolds-frequency linearity disappears at high Reynolds numbers, the frequency for this case is smaller than what could be expected. The authors believe this particular reduction of frequency at Reynolds 32068, is due to the channel effect caused by the highest outlet angle, this particular angle directs the fluid from the (MC) to the oscillator outlets, minimizing the generation of a stagnation pressure point at the (MC) converging walls, in other words, just an small amount of the kinetic energy associated to the fluid is being transformed into stagnation  
Figure 15: Dynamic effects of the (MC) inlet angle modification on the main flow parameters, Reynolds number 16034. Each graph presents three non-dimensional curves characterizing results from the baseline, the medium and highest inlet angle cases, and as a function of the dimensional time. In figure (**a**) the mass flow across the upper oscillator outlet is presented. Figure (**b**) introduces the temporal variation of the (MC) inlet inclination angle. Figures (**c**) presents the pressure at the (MC) lower inclined wall. The net momentum acting on the lateral sides of the main jet is presented in figure (**d**). Figure (**e**) characterizes the mass flow at the lower feedback channel outlet. pressure. The result is, it requires a longer time to build the required momentum at the (FC) outlets for the jet to flip. Under these conditions, the fluid is directed to the lateral sides of the oscillator external chamber wedge and flows almost parallel to them, see Figure 11a. It is at this point interesting to remember that, according to [3], the (FO) angled configuration, which is the one used in this study, looses its linearity at Reynolds 30000, this helps to explain why the curves presented in Figure 16, are not fully linear. As Reynolds number increases, the flow inside the (FO) goes from quasi-periodic to chaotic, being this the reason why linearity disappears. It is also interesting to recall, that according to [11], the fluidic oscillator internal performance is essentially the same for different outlet configurations, whether one or two outlets are considered. Stagnation Pressure at the (MC) Converging Walls and Net Momentum Acting on the (MC) Incoming Jet as a Function of the Reynolds Number  
In the present section, the net momentum acting onto the jet entering the mixing chamber will be evaluated and compared with the stagnation pressure variations at the (MC) converging walls. The momentum of the fluid acting on a given surface was defined as Equation (1). As both feedback channels, add momentum to the lateral sides of the main jet entering the (MC), Equation (1) will need to be applied to each (FC) outlet.