## 5 Results
### Relation Reynolds Frequency for All Dimensional Modifications Performed
\begin{table}
\begin{tabular}{l l l} \hline \hline
**Geometry Modification** & **Non-Dimensional Peak to Peak Net** & **Coefficient of Determination** \\  & **Momentum Amplitude at the (MC)** & \(\mathbf{(R)^{2}}\) \\  & **Incoming Jet** & \\ \hline Baseline & \(4.652E-9*Re^{1.983}\) & 0.999 \\ Highest inlet angle & \(2.706E-9*Re^{2.044}\) & 0.999 \\ Lowest outlet angle & \(5.633E-9*Re^{1.971}\) & 0.999 \\ Highest outlet angle & \(1E-9*Re^{1.929}\) & 0.989 \\ Lowest outlet width & \(4.298E-9*Re^{2.002}\) & 0.999 \\ Highest outlet width & \(2.908E-9*Re^{2.004}\) & 0.997 \\ Lowest inlet width & \(2E-9*Re^{2.006}\) & 0.997 \\ Highest inlet width & \(1.864E-9*Re^{2.038}\) & 0.998 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Equations characterizing the evolution of non-dimensional peak to peak net momentum amplitude at the (MC) incoming jet, and as a function of the Reynolds number. These equations are valid in the range \(8711<\text{Re}<32068\). \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Geometry Modification** & **Reynolds** & **Reynolds** & **Reynolds** \\  & **Number 8711** & **Number 16034** & **Number 32068** \\ \hline Baseline & 11.96 & 12.58 & 9.88 \\ Highest inlet angle & 8.72 & 9.38 & 8.1 \\ Lowest outlet angle & 9.73 & 10.71 & 9.25 \\ Highest outlet angle & 16.86 & 17.14 & 14.97 \\ Lowest outlet width & 10.63 & 10.77 & 9.32 \\ Highest outlet width & 12.93 & 13.29 & 10.88 \\ Lowest inlet width & 13.61 & 12.38 & 14.52 \\ Highest inlet width & 3.78 & 3.74 & 4.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Evaluation of the peak to peak net momentum amplitude at the (MC) incoming jet due to the pressure term, divided by the net momentum amplitude due to the (FC) mass flow term, and for the three Reynolds numbers studied. numbers. It is interesting to see that the peak to peak amplitude of the net momentum acting on the lateral sides of the jet entering the (MC), initially increases with the inlet angle increase, but as the inlet angle reaches its maximum value, the momentum amplitude slightly decreases. At the highest inlet angle, the stagnation pressure waves generated at the (MC) converging walls, are not efficiently being transferred to the (FC's) outlets. In fact, the pressure at both (FC's) outlets, is very much the same under these conditions. Regardless of the (FO) geometry modification performed, the same trend on peak to peak pressure and momentum, appeared at all Reynolds numbers evaluated, therefore, for a given (FO) modification, the same physical phenomenon is driving the oscillations at all Reynolds numbers. In order to properly understand the effect of the inlet width variation on the net momentum acting onto the (MC) incoming jet, Figure 17 is introduced. The first point to realize is that, for the lowest inlet width, the noise associated to the pressure wave generated at the stagnation points appearing alternatively at the (FC) outlets, see Figures 4 and 5, is much higher than in the rest of the cases studied. For this particular case, see Figure 5, there is a large amount of mass flow traveling backwards along the feedback channels. The authors believe, the weak pressure waves originated at the (MC) outlet converging walls, which travel along the (FC) and also inside the (MC), are being disrupted by the particularly high mass flow moving along the (FC) and in opposite direction to the pressure waves, the result is a highly noisy pressure fluctuation at the (FC) outlets. In reality, and for this particular case, pressure waves are being generated at the same time on the (MC) outlet converging walls and at the (FC's) outlet internal vertical walls, these pressure waves collide inside the (FC's) enhancing the noise spectrum. Notice as well from Figure 17 that, the noise generated reduces to a minimum whenever the maximum inlet width is being employed. For this case, the mass flow traveling along the (FC's), always goes from the (FC's) inlets to the outlets, see Figure 5, and pressure waves are not generated alternatively at the (FC's) outlet internal vertical walls.