Comparison between 1D and 2D models to analyze the dam break

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Ignacio Valcárcel LencinaTRITA LWR Masters ThesisFigure 35g. Water surface in the 2D approach at t = 5.4 sFigure 37. Flow plot of arrows at t = 5.4 s of the 2D model.The total computation time for this 2D model hasbeen 7m 30s with a processor Intel Pentium 4 CPU2.53 GHz and 1 GB RAM.A similar model with flat bottom bathymetry has beenimplemented as it was done for the 1D model todemonstrate the big influence of the bathymetry in theresults.Figure 35h. Water surface in the 2D approach at t = 5.4 sFigure 38a. Water surface at t = 0 sFigure 36. Contour plot of depths (t = 5.4 s) of the 2Dmodel.Figure 38b. Water surface at t = 2.7 s18
Comparison between 1D and 2D models to analyze the dam break wavem. The initial water level is 10 m at upstream and 5 mat downstream. The breach is 75 m wide.There is not analytical reference solution for this testcase, but in literature numerical solutions of variousauthors are available. The original example wasdescribed by Fennema and Chaudhry (1990) and thesame example has been reproduced here.Figure 38c. Water surface at t = 5.4 sFigure 38d. Water surface at t = 5.4 sFigure 40. The initial condition of the validation model solvedwith CM.ResultsThe validation model has been solved with a meshdefined by 4088 elements. An interesting view of theresults including this mesh is shown in figure 41.Figure 39. Contour plot of depths (t = 5.4 s) of the 2Dmodel with flat bathymetry.In this model with flat bottom bathymetry, the resultsare completely different. The water surface is uniformand flat. This is due to the bathymetry, it does notintroduce alterations, and thus the aspect is “smooth”.6. - VALIDATION OF TH E 2D MODELThe aim of this test case is the study of the capacity ofthe code to reproduce solutions, with particularattention to the 2D aspect of the flow motion. A200x200 m flat region represents the spatial domain.The bottom is friction less. The upstream flow is equalto 0 m 3 /s and the downstream level is set equal to 5Figure 41. Layout of the simulation at t = 6 s. Detail of themesh used in the model.Figure 42. Profile at t = 3 s.19
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Comparison between 1D and 2D models to analyze the dam break

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