HYDRO EUROPE ISIS Report. Team

Transcription

1 HYDRO EUROPE 2011 ISIS Report Team Team members: Liza ASHTON, Thibault DESPLANQUES, Jens Harold DRASER, Manuel GOMEZ (supervisor), Kyung Tae LEE, Maxime NARDINI, Jieun PARK, Jiyoung PARK & Gabor SZABO

2 Table of Contents 1. Introduction Model Set Up River Network Weir Profile Boundary conditions Upstream boundary (Analytical / HEC-HMS) Downstream boundary Run the simulation Results & Validation Calibration Conclusion References

3 1. Introduction ISIS is the full hydrodynamic simulator for modeling flows and levels in open channels and estuaries. Although we have learnt this program in this semester, we tried to follow the tutorial in the website. Then we set up and run the simulations and compared them with the results of MIKE11 as well. Figure 1: Main work space in ISIS The tasks of this river modeling are to make a hydraulic model of the Var River and to run simulations for the flood of November For validating, we checked the results of observed hydrographs at Napoleon III bridge (weir at the last weir, Branch12), and then calibrated the model for the Var low valley in respect to observed water levels at all 9 weirs. 2. Model Set Up The VarCrossSections.dat file was loaded from HydroEurope web page and took a look at the data file. Before run the simulation, we found and tried to understand the given information. Apart from Mike 11, ISIS has the distance to next section instead of accumulative chainage. 2.1 River Network Var ISIS data consists of 10 branches with 9 weir and 99 cross sections. We can check the geography of Var River from long section profile. It has 112 interpolated sections as well. If the distance between sections is far from each other, we may need more interpolated sections. The reason of this part is that the inaccuracy in ISIS 1D model. There might be instability of existing two crosses sections. Thus solution for this problem is making interpolated cross sections. Interpolated section automatically calculates a weighted average of the river or cross section properties between 2 points. 2

4 Figure 2:Initial longitudinal section before simulation Figure 3: Var river network River Profile 10 Branches 99 River sections 112 Interpolated sections 9 Weirs River Length (m) Branch Branch Branch Branch Branch Branch Branch Branch Branch Branch TOTAL Table 1: Var River profile 3

5 2.2 Weir Profile We use RNWEIR (Round Nosed Broad Crested Weir) in this model. The table shown below is the profile of weir in ISIS. It already has the coefficient of velocity with the range from 1.1 to 1.7. The lower value of the coefficient is used for weirs with relatively rough weirs, and the higher value for the coefficient can be used for very smooth weirs. This coefficient essentially stands for the change of the velocity for the water going over the weir and is normally used for calibration of the model alongside with the Manning's coefficients later. Weir No. Crest Elevation (m) Width (m) Length (m) Table 2: Weir profile 2.3 Boundary conditions In ISIS, we have Flow-Time Hydrograph at upstream and Head-Time input of the VAR river is the sea level with the value of 0 at downstream Upstream boundary (Analytical / HEC-HMS) Figure 4: Analytical Hydrograph, Max Q = Nov.5 20:00 4

6 Figure 5: HEC-HMS Hydrograph, Max Q = Nov.5 20: Downstream boundary The downstream boundary condition is equal to sea level. The type of boundary used in this model is HTBDY (Head Time). 3. Run the simulation There are two hydrographs which are derived from the Analytical method and HEC-HMS. The results were compared using two different boundary conditions in the upstream reach. First, the model was run with steady flow and then unsteady flow with a time step of 10 seconds. It is better to first run the Steady (direct) run type to see if there is everything is correct with the cross sections and with the boundaries, and then the Unsteady run type can be done. Figure 6: Simulation with steady flow 5

7 Figure 7: Simulation run with unsteady flow (fixed time) 4. Results & Validation We can visualize the result of HEC-HMS hydrograph as an initial boundary condition (long sections and cross sections). We found that there are two areas of flooding at peak time 5th Nov 20:00 in Branch2S7 and Branch 12S5 are flooded, both right banks with the maximum elevation of 83.34m and 8.58 at each. Figure 8 to Figure 12 shown below are the results of the model. Figure 8: Complete long section after running the model 6

8 Figure 9: Long section at Branch 2S7 Figure 10: Cross section at Branch 2S7 Figure 11: Long section at Branch 12S5 (Napoleon 3 Bridge) 7

9 Discharge (cms) Figure 12: Cross section at Branch 12S5 (Napoleon 3 Bridge) To validate the model, we compared the 2 different initial boundary conditions with the hydrographs at the outlet (Napoleon III Bridge). From the HydroEurope web site, we could download Q-Bridge excel file which contains the time series of flow at Napoleon III Bridge. Figure 13 represents the comparison of discharges at the outlet. And finally we decided to choose HEC-HMS graph for calibrating as it had the best fit. Discharge at the Outlet (NapoleonⅢ bridge) Observed Analytical HEC-HMS : : : : : :00 Time (hr) Figure 13: Comparison of outlet discharges at Napoleon 3 Bridge From the graph above, apart from observed results, Analytical method and HEC-HMS have quite similar results. The peak time is different as well. HEC-HMS peak time is about 3~4 hours later than observed data. 8

10 Observed HEC-HMS Level 1994 (m) Simulated Level (m) Difference Branch1S Branch2S Branch5S Branch7S Branch8S Branch9S Branch10S Branch11S Branch12S Table 3: Comparison of weir levels We also compared the water level at each weir, which also have similar results. When water goes downstream the difference between the two values are getting bigger. A large difference was found in Branch8S5 and a small difference in Branch7S4. These data will be used for following calibration part. 5. Calibration We already have a good-shaped hydrograph result from HEC-HMS simulation. So we tried to change the Manning s coefficient with appropriate values from the surface material table below. Surface material Manning s Coefficient Floodplains - pasture, farmland Floodplains - light brush 0.05 Floodplains - heavy brush Floodplains - trees 0.15 Galvanized iron Glass 0.01 Gravel Lead Table 4: Manning's Coefficient 9

11 Maximum stage(m) Figure 14: Plan view of each weir in the order of upstream to downstream (1-9) Observed M=0.036 / M=0.036 / Chainage(m) Figure 15: Comparison of weir elevations It can be seen from Figure 14 the different properties on the river along the channel. There are much more vegetation from weir 4 until weir 8. Therefore we picked two different Manning s coefficient for this ISIS model. We used the coefficient value of until weir 4, and then we put the coefficient value of until weir 8. And then we put until the end of river. At first we put 10

12 0.075 instead of 0.055, so we got quite higher values in the middle of the river. Since in the middle of the river has quite vegetation, so finally we chose to put for better modelling. 6. Conclusion From this ISIS simulation, we could find the flooding area through the graph and animation. So, we need a structural analysis. Because this flooding event happened more than 15 years ago. Moreover a lot of parameters have been changed, such as weir coefficients and Manning s coefficients. And this model is quite matched with the observed data except the weir 2&3 which are destroyed before. From the modeling, both MIKE 11 and ISIS show the similar result, the max out flow is m 3 /s (MIKE 11) and m 3 /s (ISIS). ISIS is more easier than MIKE11. Because we don t need to make a network first in ISIS. So it might save time if there is a huge and long river network like Var river. 7. References _Hydraulics_Using_ISIS.htm Figures & Tables Fig.1 : Main work space in ISIS Fig.2 : Initial long section before run the simulation Fig.3 : Var river network Table.1 : Var river profile Table.2 : Weir ProfileFig.4 : Analytical Hydrograph, Max Q=3,671,78 Nov.5 20:00 Fig.5 : HEC-HMS Hydrograph, Max Q=3,436.3 Nov.5 20:00 Fig.6 : Run the simulation with steady Fig.7 : Run the simulation with unsteady(fixed tiem) Fig.8 : Long sections after run the model Fig.9 : Long section at Branch 2S7 Fig.10 : Cross section at Branch 2S7 Fig.11 : Cross section at Branch 12S5 (Napoleon III Bridge) 11

13 Fig.12 : Cross section at Branch 12S5 (Napoleon III Bridge) Fig.13 : Comparison of outlet discharge at Napoleon III Bridge Table.3 : Comparison of Weir levels Table.4 : Manning s Coefficient Fig.14 : plane view of each weir from upstream to downstream(1-9) Fig.15 : Comparison of Weir elevation 12