## 3 Results
### Validation
Hence, the model is valid for studying effects that would take place on the experimental rig when tested. Figure 6: Mach number distribution at stator midspan. ST and RT; VGT30; 0.5 mm tip height. The VGT30 case was also analyzed for vanes which are both affected and not by elements on the volute. Figure 8 shows how **V8** had a \(C_{p}\) near 0 for most of the PS after the initial distortion due to the stagnation point previously observed in Figure 6. In the ST model, this is underestimated, and the value is slightly lower, hence having a compression on that side which can be attributed to the acceleration of the flow. On the SS, the blockage effect at half chord is represented with exactitude. **V5** shows a \(C_{p}\) distribution that behaved similar to **V8**, but PS shows a more accentuated deceleration for the first 20% of the chord because of the presence of the screw. The vane affected by the screw on its SS, **V6**, shows such a good agreement between models, especially on SS all along the chord. Meanwhile, on PS near LE, the effect of the screw creates a brief area of detachment, reattached after the 10% of the chord and colliding results between models. In addition, it is noticeable how \(C_{p}\) profiles from different VGT openings are different. Still, the variation of flow conditions did not affect these pressure coefficients much for a single position. The study that deals with Reynolds through the clearance is remarkable from the perspective of obtaining information on how flow behaves over the tip of the vane. Different methodologies were performed to check how flow behaves between ST and RT to validate if there exists a resemblance to that behavior. Firstly, a macroscopic behavior of the flow is depicted in Figure 9 for VGT60 and in Figure 10 for VGT30. Uniform-sized vectors are drawn at a plane that crosses the tip gap at its mid-height. RT can be noticed by the presence of the screw in the form of a blank circle in which the flow stagnates. For VGT60, there is a resemblance between how the flow crosses the vane over the gap from the pressure to suction side from mid-chord to TE. However, in the RT, the tendency of the flow to cross over the gap is higher because of the influence of the rotor. For its part, VGT30 has similar behavior, but as the trend of this whole study indicates, the resemblance between RT and ST is higher, and the impeller is less affected than for wider openings, where the stator vanes TE are closer to the rotor wheel. Figure 7: \(C_{p}\) for each studied vane. ST and RT; VGT60; 0.5 mm tip height. In the figure, legend colors stand for each case, while shapes in gray determine each of the vane faces. The distortion in the flow direction on the clearance between ST and RT can be quantified by defining a flow angle direction, \(\phi\). This angle is measured at the mean chord line of the vane, as shown in Figure 10(a). It was measured as the direction of a particle placed in the mean chord line for every 5% of chord distance for both ST and RT. As depicted from the scheme of the vane, \(\phi\) is non-dependent on the vane position. It is defined within its chord line, no matter which \(\alpha\) has the referred vane. With this definition, the outlet flow angle with which the flow leaves the vane can be better understood, and the influence of not having a rotor in ST is quantified. Figure 8: \(C_{p}\) for each studied vane. ST and RT, VGT30; 0.5 mm tip height. In the figure, legend colors stand for each case, while shapes in gray determine each of the vane faces. Figure 10: Flow direction over the tip. ST and RT; VGT30; 0.5 mm tip height. Figure 9: Flow direction over the tip. ST and RT; VGT60; 0.5 mm tip height. In Figure 11b, the flow direction angle, \(\phi\) for **V7** at two different vane positions, VGT30 and VGT60, can be seen. For the VGT30 case, a variation from the chord beginning exists that causes the flow in ST to be underestimated in its turning direction.