# Novel Fluidic Oscillator Evaluation Considering Dimensional Modifications
## 6 Results
### Feedback Channel Dimensional Modifications (2D-CFD)  
As in the previous section, before analyzing the results obtained from the modification of the feedback channels' widths, it is relevant to evaluate the possible influence of other dimensional parameters affected by this primary modification. As observed in Figure 3b, decreasing the FC width significantly increases the FC length. For the minimum feedback channel width considered, FC1 (see Table 4), the FC width is 66.6% smaller than the baseline case, and the FC length increases by 44.4%. For the maximum FC width evaluated, FC4, the FC width increases by 33.3% and the FC length decreases by 21.8% compared to the baseline case dimensions. Therefore, the FC width variation certainly affects the FC length, but as the fluid is considered incompressible, the pressure waves travel instantaneously, and so, the effects of the FC length need to be seen as less relevant than the FC width effects, particularly when considering that the FC width drastically affects the forces acting onto the jet as it enters the mixing chamber. Note as well that no surface roughness is considered in the CFD simulations; therefore, the shear stresses appearing along the feedback channels (and so the pressure drop between the feedback channels' inlets and outlets) need to be regarded as negligible. In fact, in the numerical studies under incompressible flow conditions performed by [31; 32], the FC length effect was evaluated, but no noticeable FO dynamic effect was observed in either of these two investigations. The effect of FC length must be studied under compressible flow conditions, as in [24]. Pressure and velocity fields for the minimum, FC1, and maximum, FC4, feedback channel widths evaluated are presented in Figure 15 and Figure 16, respectively. In both figures, the respective oscillation cycle is divided into four equidistant time steps. The first thing that catches the eye is that for the smallest FC width there is no FC reverse flow, while a large reverse flow is observed in the FC4 case; in fact, for this case, large flow in both FC directions is clearly observed. The jet inside the MC in FC1 is more uniform, the fluid follows the long MC internal walls. On the other hand, a considerable random movement of the jet inside the MC is observed in FC4; the wide FC width favors such randomness. The pressure fields are very similar in both cases, but due to the greater stability of the jet in case FC1, the periodic vortical structures forming inside the MC are much smoothly defined in this particular case. Four videos presenting the velocity and pressure fields for the minimum and maximum FC widths evaluated are provided in the Supplementary Materials. The major flow stability observed in the FC1 velocity fields is further noted when evaluating the net pressure and mass flow forces acting on the jet as it enters the MC; Figure 17a and b, respectively. It is seen that the net pressure force curve for the FC1 case is much smoother than the rest of the curves; it is also seen that the peak-to-peak amplitude is the smallest from the four cases evaluated. This amplitude grows with the FC width, although for the largest FC width, FC4, it becomes much more random. Clearly, for the maximum FC width studied, the degree of freedom of the jet inside the MC is too large, generating a higher degree of oscillation randomness, observed in the scattered pressure curve. Similar conclusions are obtained when evaluating the net mass flow forces acting on the jet at the FC outlets: the peak-to-peak amplitude grows with the FC width and shows a considerable increase at FC4, with the associated randomness also increasing. Regardless of the FC width studied, the net mass flow forces are about a third of the corresponding pressure forces. The FO and FC outlet mass flows for the four FC widths studied are presented in Figure 18a and c, respectively.