**5. Dam break flooding flow modeling in real region**

To illustrate the techniques of the application of numerical modeling of large-scale hydrodynamic computations, we consider the problem of computing the flood process in the areas near the dams of the Andijan and the Papan reservoirs (see **Figure 12**).

It is to be emphasized here that the situation of a real breakthrough of the dam and the flood of the areas at the lower level is not modeled here but the fundamental possibility of using the above technology under the availability of necessary topography data is demonstrated. The topography data of Digital Terrain Elevation Data [8] were used in computations, which were converted subsequently into the STL format. The hexahedral background grid generated with the aid of the utilities blockMesh and snappyHexMesh of the OpenFOAM package was transformed into a three-dimensional surface, which is employed for modeling the flood process (**Figure 13**).

For the Andijan reservoir, the computational field had the sizes 6000 × 4000 × 1500 m, the physical modeling time amounted to about 9 h for the 120 × 120 × 80 grid. **Figures 14** and **15** show different stages of the flood in areas with real topology. The red corresponds to a pure

**Figure 12.** Maps of the Andijan (left) and Papan (right) reservoirs.

**Figure 10.** Water flow heights at points Н2 (left) and Н4 (right).

the water returns from the back wall after the moment of time *t* ≈ 1.8 s. After that, the numerical data (solid lines) prove to be somewhat higher than the experimental ones (markers). At the moment of time of *t* ≈ 5 s, the secondary wave reaches the neighborhood of the probe Н2. This time is, however, equal to about 5.3 s at the numerical modeling. The general character of

the variations of the numerical and experimental data nevertheless coincides.

68 Dam Engineering

**Figure 9.** Comparison of numerical (left) and experimental [7] (right) data at the moment of time *t* = 0.6 s.

**Figure 11.** Pressure at points Р2 (left) and Р7 (right).

water flow, and the blue corresponds to air flow (there is no water flow in blue regions). It is seen in **Figure 14** that the leading front of water flow reaches during 240 s the lower boundary of the computational region passing a distance of about 6000 m, covers the most part of the area located downstream.

The computational field for the Papan reservoir has the sizes 5000 × 5000 × 1300 m (see **Figure 15**).

The total computing time in the case of the 50 × 60 × 30 grid amounts to about 5 h. As is seen in **Figure 15**, after the moment of time *t* ≈ 200 s there forms a reverse flow (**Figure 15d**

and **c**) and after the moment of time *t* = 260 s; it separates into two parts—one part is in the zone of reverse flows and the other continues its flow in the lower part of the river bed. The computations show that about 60% of the entire initial water volume remains in the zone of

Large-Scale Modeling of Dam Break Induced Flows http://dx.doi.org/10.5772/intechopen.78648 71

The results of the mathematical modeling of complex hydrodynamic phenomena on the basis of unsteady three-dimensional Navier-Stokes equations describing the dynamics of a gas-liquid mixture with free boundary have been presented. The adequacy of the employed model has been verified by the example of the classical problems of computational fluid dynamics. Special attention has been paid to the accuracy of the computation of the water flow level and the gas-liquid flow pressure on the reservoir walls. The efficiency of the employed technology has been illustrated by the example of modeling the breaks of the dams of the Andijan (Uzbekistan) and Papan (near the Osh town, Kyrgyzstan) reservoirs. The developed technology is universal and can be used for the flood modeling for a real relief. It is shown that the

The Dam break flooding flow modeling in real region part of this chapter was done within the framework of the Fulbright exchange program of the US State Department. Authors gratefully thanks to of Prof. Greg Olyphant from the Indiana University, Bloomington, USA for his supervision and to Sally L. Letsinger, PhD, research Hydrogeologist of the Center

reverse flows.

**6. Conclusions**

relief features are a substantial factor.

**Figure 15.** Flow pattern for the Papan reservoir.

**Acknowledgements**

**Figure 13.** Three-dimensional surface of the Andijan (left) and Papan (right) reservoirs areas.

**Figure 14.** Flow pattern for the Andijan reservoir.

**Figure 15.** Flow pattern for the Papan reservoir.

and **c**) and after the moment of time *t* = 260 s; it separates into two parts—one part is in the zone of reverse flows and the other continues its flow in the lower part of the river bed. The computations show that about 60% of the entire initial water volume remains in the zone of reverse flows.
