## 5 Conclusions  
This paper presents a 3D experimental and numerical investigation of the dam-break wave propagation during its initial stages in an enclosed domain over dry and wet beds with two different tailwater levels. Image processing for flow measurements yields 3D unsteady flow behavior economically and straightforwardly during the laboratory tests.  
The findings show a significant difference in the propagation of wavefronts between the dry and wet domains. The velocity of the wavefront was faster for dry-bed conditions than the wet-bed cases. In addition, as the tailwater depth increased, the wavefront velocity decreased. This is due to the higher resistance of the higher water depth to the propagating waves. However, after reflection from the downstream wall, the wavefront velocity of the negative wave increased as the depth ratio increased. During the early dam-break stages, intense turbulence was observed for the dry-bed case. This turbulence, generated from the bottom friction, caused a significant energy dissipation on the channel end wall. Also, in the wet-bed cases, early wave breaking caused turbulence and energy dissipation in the domain. Therefore, as the depth ratio decreases, wave breaking occurred earlier.  
The measured results were then compared with those of numerical simulations, and reasonable agreements were achieved. Herein, the CFD package, FLOW-3D, produced good results in predicting the 3D dam-break flow propagation in an enclosed domain over dry and wet beds, both with the RANS and the SWEs. However, as expected, although the SWEs present the advantage of requiring less time and computational resources, their assumptions are not applicable at the initial stages of the dam-break and at the front of the dam-breaking wave and near structures (due to the highly transient nature of dam-break flows, the 3D effects, and the involved turbulence). The modeling of such complex flows should be based on 2D or 3D models that use the Navier-Stokes equations. SWEs are sufficient tools for predicting the water arrival at large time or far from the dam, but not to simulate high free-surface gradient flows or to calculate the pressure-load on structures. Fortunately, the increasing computational power provided by the recent multiprocessor computers and the access to modern massively parallel supercomputers allow for the resort to more complex 3D numerical models, which can more accurately reproduce the physical processes, when needed, and in real-scale cases.  
In addition, despite the potential power of numerical simulations, physical models always constitute a useful tool to investigate different features under controlled conditions and to better understand several features of the physical processes, especially when complex real problems have to be simulated. The laboratory results presented here can be valuable to validate 3D numerical models or assist the design, due to difficulties in getting field data on dam-break flows.  
Conceptualization, S.K., S.E., H.G., K.D., A.Y. and G.V.; methodology, S.K., H.G., K.D. and A.Y.; software, S.K., S.E. and G.V.; validation, S.K., S.E. and G.V.; formal analysis, S.K., S.E. and G.V.; investigation, S.K., S.E., H.G., K.D., A.Y. and G.V.; resources, S.K., S.E. and G.V.; data curation, S.K.; writing--original draft preparation, S.K., H.G., K.D. and A.Y.; writing--review and editing, S.K., S.E. and G.V.; visualization, S.K., S.E. and G.V.; supervision, S.K.; project administration, S.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available upon reasonable request.  
The authors declare no conflict of interest.