# Impact of Mesh Resolution and Temperature Effects in Jet Ejector CFD Calculations
## 3 Results
### Analysis of Different Meshes--Courser and Refined Meshes  
This part of the study analyzes the considered constant boundary values (\(\rm p_{P}=35\) bars, \(\rm T_{P}=380\) K, \(\rm T_{s}=313\) K, and \(\rm\pi_{sp}=0.26\)) and the two meshes. The _refined_ mesh used in this study is the mesh version of case no. 8 from Table 3, which features a notably high resolution. It is compared with the results obtained with the _coarser_ mesh (case no. 3 from Table 3) to see the differences between the \"traditional meshing\" (with cell numbers similar to our _coarser_ mesh) with the high-resolution meshing proposed in this work (_refined_).  
As can be seen in the graph in Figure 7, the results obtained with the _coarser_ mesh and the adaptive _refined_ mesh differ. The distortions can be seen in the comparison of Mach number distributions of _coarser_ and _refined_ meshes, illustrated in Figure 8 below, which highlights the impact on the Mach number scene representation with the different mesh precisions, _coarser_ on the top and _refined_ on the bottom. These inaccuracies result from the inability of the _coarser_ mesh to resolve steep gradients in pressure, temperature, or velocity accurately, especially near shock regions and boundaries. Additionally, it can lead to unclear or inconsistent readings of flow behaviors, such as turbulence levels or boundary layer separation [32].  
Similarly, the larger inaccuracies while using the coarser mesh observed in Figure 8 produce differences in the mass flow results (affecting entrainment ratios). These differences in entrainment ratios translate into different representations of the working map line. Figure 7 shows the comparison between the \(\rm\pi_{sp}=0.26\) pressure ratio lines obtained using the coarser (stars) and the refined (circles) meshes. In the graph, we can see that the maximum entrainment ratio (critical conditions) in both cases is the same (at \(\omega=1.17\)). However, the subcritical zone for the _coarser_ mesh starts earlier, at \(\rm\pi_{op}=0.355\), while for the _refined_ mesh the transition occurs at \(\rm\pi_{op}=0.375\). The lines get closer to each other towards the negative entrainment ratio values as the negative slope in the _refined_ mesh is higher than in the _coarser_ case. Furthermore, this negative slope (subcritical zone) is more constant in the case of the _coarser_ mesh than in the case of the _refined_ mesh, where a certain wavy shape can be observed in this negative slope. As shown in the figure, a _refined_ mesh shows  
Figure 7: The lines of \(\rm\pi_{sp}=0.26\) for the comparison between the coarser and refined meshes.  
details of the ejector behavior that cannot be observed with _coarser_ meshes. It shows that the better-refined mesh is able to better catch the intricate shapes of the oblique shock waves and how they affect the entrainment ratios obtained.  
In order to observe, in more detail, the difference in the obtained results between the _coarser_ mesh and the _refined_ mesh, two cases have been selected and are represented in Figure 7 as cases A and B. These two cases are close cases with similar pressure ratios, and the comparison of the Mach number distribution in both cases can be seen in Figure 8.  
In the upper part of Figure 8, the Mach number distribution is shown for both cases, while the lower part presents the Mach number difference between scenes at points A and B (from Figure 7). In these scenes, the improvement in results when using the refined mesh can be observed, especially in the representations of the oblique shock waves. In the lower part of the figure, the differences in Mach number distributions and values between the scenes for cases A and B are represented. It can be observed that the most important differences in the results occur throughout the supersonic jet, especially in the area with higher Mach number values. These differences in the distribution of shock waves in the jet cause slight discrepancies in the results and produce the differences in the entrainment ratios observed in Figure 7.