## 4 Conclusions  
In this study, we investigated the impact of geometric modifications to the bottom topology downstream of the wave on the outflow behavior and wave stability of the _Fuchslochtvelle_, an artificial standing wave used for river surfing. A computational fluid dynamics (CFD) simulation in STAR-CCM+ was set up to model various configurations of baffles and inlays to minimize recirculation zones and enhance surfer safety.  
* A realistic 3D-CAD model of the _Fuchslochreule_ was created. A total of 16 configurations were simulated, including both symmetrical and asymmetrical baffle and inlay configurations. The default configuration, intended to represent the current state of the _Fuchslochreule_, exhibited similar recirculation patterns to those reported by surfers.
* In the symmetrical group, the reduction in these recirculation zones was most effectively achieved by placing baffles on the inlay at 2 m. In contrast, in the \(ACB\) and \(SCBW\) groups, recirculation was best minimized by a combination of baffles at the wall and baffles on the inlay at 3 m.
* We simulated a baffle geometry that was subsequently constructed and installed in the _Fuchslochreule_. Although this baffle was installed at 3 m rather than the 2 m suggested by the simulations as the optimal placement, it still resulted in a significant reduction in the undesired recirculation zone. This reduction in recirculation was also reported by experienced surfers.
* The results of this study demonstrate that baffles placed on the inlay at 2 m and on the sidewalls can reduce recirculation zones by more than half in terms of vorticity. This approach can be adopted by other wave operators to improve flow conditions in their installations.
* For future work, priority should be given to validation through in situ measurements to further enhance confidence in the presented simulations. Additionally, the impact of geometric simplifications, such as the neglected inflow basin, should be investigated. Lastly, improvements to the numerical setup should be considered to enhance stability, realism, and accuracy.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15063127/s1](https://www.mdpi.com/article/10.3390/app15063127/s1)]([https://www.mdpi.com/article/10.3390/app15063127/s1](https://www.mdpi.com/article/10.3390/app15063127/s1)), Figure S1: Visualization of the \(y+\) values in one example for the canal (top) and real volume (bottom); Figure S2: Simulation volume for the grid independence study. Figure S3: Simulation volume for the grid independence study.  
Conceptualization, M.D., T.K., J.B., M.S. and N.N.; methodology, J.S., B.T., S.K. and M.D.; validation, M.D., T.K., J.B., S.K., B.T. and J.S.; formal analysis, B.T. and J.S.; resources, M.D., T.K. and J.B.; data curation, B.T. and J.S.; writing--original draft preparation, B.T. and J.S.; writing--review and editing, M.D., T.K., J.B., S.K., N.N. and M.S.; visualization, B.T. and J.S.; supervision, M.D.; project administration, M.D. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data available on request from the corresponding author.  
The authors declare no conflicts of interest.