# Analysis of Cavity Corner Geometry Effect on Recirculation Zone Structure
## 3 Results and Discussion
### Investigation of Flow Topology in the x-z Plane  
Flow streamlines and velocity \(u\) profiles measured in the x-y plane are given at \(y/h_{1}=0.5\) (in Figures 11 and 12). At Re = 100, lateral vortices are observed in all investigated cases. Note that longitudinal dimensions differ in every investigated channel due to geometry limitations. For example, the growth of lateral vortices in Ch3 is determined by increased velocity in the centre of the channel; therefore, more kinetic energy is transferred to lateral vortices, thus increasing their size. Further, since the recirculation zone in Ch3 is smaller than in other cases, the difference in reverse flow distribution between Ch3 and Ch1/Ch2 is evident, as can be observed from the x-z plane velocity \(u\) profiles (Figure 12). In Ch3, the separated shear layer reattaches to the cavity bottom (Figure 6), and the recirculation zone is smaller than in other cases. Therefore, the effective flow cross-section increases in the cavity. Due to more space for flow development above the recirculation zone, the velocity at \(y/h_{1}=0.5\) is more than three times greater than in other cases at the middle part of the cavity.  
When the flow approaches the trailing wall, the velocity differences between the investigated channels become lesser, yet are still notable. However, as the Re increases to Re = 1000, the impact of geometry on flow topology becomes less significant because recirculation zones become of comparable size. The lateral vortices formed near the leading wall are displaced towards sidewalls in Ch3 compared to Ch1/Ch2 because the trailing cavity wall is being bent inside the cavity, and from the resulting space restrictions the  
Figure 11: Velocity contours in the x–z axis.  
Figure 10: Pressure drop in Ch1, Ch2 and Ch3.  
vortex centre is stretched across the cavity. A lesser effect is observed in Ch1. The opposite is observed in Ch2, where lateral vortices are close to each other and in the vicinity of the cavity mid-plane when the trailing wall is bent outside, and the vortex core is less restricted.  
Turbulence intensity profiles at \(\mathrm{Re}=1000\) are given in Figure 13. \(\mathrm{Re}=1000\) is presented due to the flow structure being considered fully developed in the cavity. It is known that increased \(Tu\) values may cause flow instabilities and the presence of secondary flows [16]; therefore, the distribution of \(Tu\) is investigated to analyse flow stability.  
Out of all investigated channels, the highest increase of \(Tu\) is observed in Ch2. This implies that the fully curved cavity bottom corners cause the flow to become less stable, i.e., the flow tends to fluctuate. Gradually decreasing the cross-section (near FFS) strengthens interactions between the recirculation zone centre and the main flow. Thus, flow perturbations near the recirculation zone centre occur; therefore, peak \(Tu\) is observed at \(x/h_{1}=3.5\). This applies to \(\mathrm{Re}=500\) and \(\mathrm{Re}=1000\); therefore, its magnitude does not depend on \(\mathrm{Re}\). Additionally, increased \(Tu\) implies that the flow becomes less two-dimensional [17]. Conversely, the opposite situation is seen in Ch3, where \(Tu\) decreases in the recirculation zone, implying that the recirculation zone is more stable.