Numerical Simulation of Triangular Dam Overflow

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Vol. 54, No. 3, September, 2020

NUMERICAL SIMULATION OF TRIANGULAR DAM OVERFLOW

T. A. Fedorova,1 E. S. Vasil’eva,2 and V. V. Belikov3

Translated from Gidrotekhnicheskoe Stroitel’svo, No. 4, April 2020, pp. 30 – 33.

The STREAM 2D CUDA model is validated against high-precision measurements on a Crump weir using meshes of different cell sizes. The simulations demonstrated realistic results for coarse meshes. This allows similar simulation for real objects. Keywords: numerical simulation; Crump weir; weir crest depth.

— distance from the weir crest to the beginning of the flume is 4.52 m; — roughness of the bottom and walls (glass, stainless steel, PVC) is 0.009 m1/3 · sec. A certain water flow was created in the flume, and, after overflow stabilization, no fewer than 100 measurements were made and the average value was calculated. High-precision level sensors (0.01 mm accuracy in the range from 0 to 455 mm) were used to measure the flow depth the following points: — at a distance of 0.44 m upstream from the weir crest-geometrical head T over the flume bottom; — at the weir crest hcr; — at a distance of 0.49 m downstream from the weir crest-flow depth in the contracted cross-section hc. The computations were performed using STREAM 2D CUDA software [2, 3] for the same flow rates as in the experiment. Three meshes with different cell sizes (1, 3, and 12 cm) were used (Fig. 1). The numerical simulation proceeded as follows. The water flow rate was specified on the upstream side, and the weir coefficient m = 0.3 was specified on the downstream side. The boundaries of the simulation domain were chosen rather far from the weir so that they did not affect the accuracy of calculation. The initial condition (level) was specified so that the computation did not start with dry bottom sections. The flow became steady quite rapidly: in 1 to 5 min. The output file contained flow depth values at the chosen characteristic points. Figure 2 shows the calculated results for three cycles of experiments with different water flow rates. Table 1 and Fig. 3 compare the calculated results for the fine small mesh (cell size 1 cm) and the experimental data.

Dam overflows are frequent causes of accidents at hydraulic structures. The current trends are toward the use of as fine as possible meshes to increase the accuracy of overflow analysis. This approach depends on computing power. Here we propose an alternative method for increasing the efficiency of numerical simulation based on a new algorithm. A dam is modeled by a Crump triangular weir. Zuikov [1] measured with high accuracy the flow characteristics for a weir with the following parameters: — crest height is 0.07 m; — crest width is 0.311 m; — ratio of crest height to upstream slope length is 1:2; — distance from the beginning of the slope to the crest is 0.120 m; — ratio of crest height to downstream slope length is 1:5; — distance from the end of the downstream slope to the crest is 0.3 m; — weir height from the flume bottom is 0.01 m; — distance from the beginning of the weir to th