unsteady Flow Analysis

[Daniel Mack]

I am working on a stream model for which I have the corridor modeled in Hec-Ras 3.0. It is my goal to show the degradation of stream flow along the corridor for an earth embankment dam catastrophic failure. I can execute the steady flow analysis for realistic stream flows, and the unrealistic peak flow from the catastrophic Dam Failure (as steady state). In the unsteady analysis I have entered the "Breach" generated FLOW hydrograph, and tried to execute the analysis for several "boundary marked critical fro time step interval" time intervals as recommended to prevent the program from going unstable while executing the analysis. I cannot even get the "post processor" to run. The message I get is, " three internal boundary curves have been generated, and will not be recalculated". Is there anyone who knows how i might proceed to get some kind of answer from the program?

Thanks to all who even take the time to read this!

Happy holidays to the Hard working engineers!

Daniel Mack

[Chris Maeder]

Note that UNET, the Unsteady NETwork model, really cannot correctly model a floodwave hydrograph that results from a dam failure. The wave front has to be tracked with a very small time step and computational distance, and UNET does not automatically resize these values during its analysis.

So, even if you get the HEC-RAS output post-processor to operate, I don't think that the computational results will be accurate enough to represent the floodwave.

Sincerely,

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