# Influence of Incident Shock on Fuel Mixing in Scramjet
## 4 Results and Discussion
### JET Flow Structure
Additionally, the point at which the incident shock wave intersected with the bow shock was located near the upper wall surface, close to the terminal end of the bow shock. Consequently, this intersection had a negligible effect on both the strength and the inclination angle of the bow shock. Figure 20 illustrates that, in case 5, the bow shocks produced by the injection manifested an arcuate configuration. The position in which these shocks intersected differed across planes, with the intersection at the z = 0.042 plane notably situated further downstream than its counterpart at the z = 0 plane. Conversely, in case 4, the points of  
Figure 18: Streamlines distribution for different cases of z = 0 with point of separation. interaction between the incident shock wave and the bow shocks on both the z = 0 and z = 0.042 planes exhibited a near-complete congruence in the streamwise and vertical axes. This phenomenon could be ascribed to the more expansive separation region preceding the injection culminating in a comparatively diminished arc of the bow shock. The interaction between the bow shock and the boundary layer present on the upper wall surface has the potential to modify the characteristics of the boundary layer. Under the influence of a sufficiently strong shock, the boundary layer may exhibit thickening or experience separation from the wall [41]. As illustrated in Figure 19, at planes z = 0 m and z = 0.042 m, the interaction between the bow shock and the boundary layer on the upper wall results in a modification of the velocity distribution in the boundary layer. Figure 21 presents an iso-surface where the streamwise velocity is constant at 1000 m/s, colored by the distance from the upper wall surface. This coloration method aimed to reveal the magnitude of changes in the boundary layer due to its interaction with the bow shock wave, offering a clearer visualization of the shockwave's impact on the boundary layer at the upper wall. In Figure 21, two distinct black lines specifically identified the projected locations of the z = 0 and z = 0.042 planes onto the aforementioned upper wall surface, thereby delineating the precise spanwise positions of these respective planes. Within the context of case 5, a discernible interaction between the shock wave and the boundary layer was evident at point A. At this juncture, the spanwise expansion of the boundary layer's thickening manifested as a linear formation. Upon cross-reference with Figure 15, it became  
Figure 19: Shock wave with velocity isolines for different planes. Figure 20: D shock wave. unequivocally clear that the observed modification in the boundary layer's thickness at this specific juncture could be conclusively attributed to the reflection phenomenon of the incident shock wave. At point B, a noticeable change in boundary layer velocity re-emerged, marked by a substantial thickening and an arc-like pattern of thickness alteration. This characteristic highlighted the location as a zone of interaction between the bow shock wave, produced by the jet flow, and the boundary layer along the upper wall surface--an area analogous to point A in case 4. Due to the period of the incident shock wave, the upstream region of the interaction between the bow shock wave and the upper wall surface was not influenced by the incident shock wave, resulting in no significant change in boundary layer velocity. However, in case 5, the scenario differed: The incident shock wave engaged with the boundary layer prior to the bow shock wave's arrival at the upper wall. This early interaction prompted a thickening of the boundary layer ahead of the bow shock wave's contact point. Furthermore, the more compact separation region in case 5 lessened the separation shock's influence on the bow shock wave, enabling it to retain its intensity. As a result, an increased amount of energy was imparted to the boundary layer, significantly increasing the boundary layer's thickness.