DAMBRK Steady State Model

Dear Mr Maeder,

Thank you for your Email dated 4th November. The comments you gave were helpful. In your Email you said it would be helpful for you to have a copy of the data I am trying to test. Please find attached the input data named PICHI02.DBK. I would be interested if you could look at this model and suggest where the errors maybe. The analysis runs but an error message appears stating a floating point error. Then the program prompts a question asking if I want to abort the computation. I continue and when I view the data a Non-Convergence message appears repeatly and states the cross section numbers in error. These cross sections are interpolated by the program so they can not be accessed and ammended. I have simplified the cross sections that I have input as much as possible.

There was another quire I have. On the output graph "Flood Crest Depth Plot" what does the Incremental Increase represent as the manual carries no information about it.

Many Thanks
JUSTIN ROOKARD
Consultores Pichi Picun Leufu

Dear Justin :

I have looked over your DAMBRK model and have the following observations:

1. You have set up this model as a steady state model, but in reality it is not. For example, you have a steady state inflow hydrograph to the upstream reservoir of 1,000 cms, but you have 2,000 turbine outflow from the reservoir. So, the WSEL in the reservoir is lowering from time 0.0.

2. You have set the time of failure at 1.00 hour, and the reservoir initial WSEL and the reservoir failure WSEL at the same value. However, as I pointed out in #1, above, the dam will not fail since the reservoir WSEL immediately drops due to more outflow from the reservoir than into it.

3. Note that your channel bottom top widths are very wide. This could cause modeling problems if you change the model to lower flow values.

4. Your model stops running after 18.150 hours because it has run out of time steps (1,200). You need to increase your time step size (make it larger) in order to get to the end of your inflow hydrograph (24 hours), or move to the Professional Version of BOSS DAMBRK which has 9,000 time steps.

5. The model is failing soon after running out of time steps since the model is really non- standard (i.e., not a flow situation that is typically run). However, BOSS DAMBRK can be forced beyond the problems it ran into, as you have successfully done.

6. Note that the incremental increase is the increase in depth from initial flow conditions by the flood hydrograph caused by the failing of the dam. In your situation, it is not really present since the dam never fails.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com