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Tham khảo tài liệu 'a finite element scheme for shock capturing part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Table 3 Test Conditions For The Dam Break Case Condition Value t 1.0 1.5 a as 0.25 0.50 n 0.009 v vs 0.001 0.01 m2 sec g 9.802 m sec2 Át 0.05 sec The numerical grid is shown in Figure 23 and contains 698 elements and 811 nodes. This grid was reached by increasing the resolution until the results no longer changed. The most critical reach is in the region of the contraction near the dam breach. The basic element length in the channel is 0.1 m and there are five elements across the channel width. For the smooth channel case Bell Elliot and Chaudhry 1992 used a 1-D calculation to estimate the Manning s n to be 0.016 but experience at the Waterways Experiment Station suggests that this value should actually be 0.009 which seems more reasonable. The test results for stations 4 6 and 8 are shown in Figures 24-26. Here the time-history of the water elevation is shown for the inside and outside of the channel for both the numerical model at t of 1.0 and 1.5 and the flume. The inside wall is designated by squares and the outside by diamonds. Of particular importance is the arrival time of the shock front. At station 4 the numerical prediction of arrival time using cq of 1.0 is about 3.4 sec which appears to be about 0.05 sec sooner than for the flume. This is roughly 1-2 percent fast. For Oị of 1.5 the time of arrival is 3.55 sec which is about 0.1 sec late 3 percent . At station 6 both flume and numerical model arrival times for at of 1.0 were about 4.3 sec and for station 8 the numerical model is 5.6 sec and the flume is 5.65 to 5.8 sec. With otj. set at 1.5 the time of arrival is late by about 0.2 and 0.15 sec at stations 6 and 8 respectively. The flume at stations 6 and 8 has a earlier arrival time for the outer wave compared to the inner wave. The numerical model does not show this. In comparing the water elevations between the flume and the numerical model it is apparent that the flume results show a more rapid rise. The numerical model is smeared somewhat in time .
