2D Simulation - Error in Computation Log File

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2D Simulation - Error in Computation Log File

sprousegw
Hello everyone.

I have an unusual problem that I have never encountered before. When viewing my results in the computation log file, it reports that my 2D Inflow is Infinity and my error is -Infinity (see attached screenshot). I am running simulations for a certain area with different annual exceedance probabilities. I have already run two simulations with the same 2D flow area, same boundary conditions, same terrain and land cover, etc. The only thing that varies among the simulations are the inflow hydrograph and the precipitation hyetograph. For the first two simulations I ran, I received no runtime errors and my computation log files looked fine. However, for this last run I did, I am receiving this infinity reporting in my computation log file, but I don't know why? I received no runtime errors and have checked my results in HEC-DSS viewer and they look fine. It should also be noted that the magnitude of the precipitation event and the inflow hydrograph for this simulation is lower than both of the other simulations ran with no issues. Anyone know why this could be happening?

Thanks a ton!

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Re: 2D Simulation - Error in Computation Log File

cameron
Are you running it with the full momentum or diffusion wave solver?  Have you tried adjusting your time step?
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Re: 2D Simulation - Error in Computation Log File

sprousegw
Hi Cameron, thanks for the response. I'm running it with the diffusion wave solver. The time-step should be sufficiently low (30-seconds) as I have already run two other simulations without getting this error. It's very curious to me because the other two simulations I ran had much more water in them caused by inflowing hydrographs with more volume of water and excess precipitation hyetographs also with a larger volume of water. Everything between the simulations is the exact same expect for the hydrograph and hyetograph. Why would I encounter this issue for one of the simulations and not the others, and why would that happen for the lowest flow event?

My thought is that simply something went wrong during the calculations (maybe the computer got interrupted somehow) and thus spit out that infinity error, but I'm not sure. Any further thoughts would be greatly appreciated!
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Re: 2D Simulation - Error in Computation Log File

cameron
The diffusion wave solver does not give many warnings when running and almost never crashes even if the results are terrible.  I prefer to use the full momentum which does crash if the time step is to large.  I would switch to the full momentum to see what happens.  I would also look at the velocities generated from the diffusion wave run to see if there are any that are unrealistic.
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Re: 2D Simulation - Error in Computation Log File

sprousegw
Hi Cameron, thank you for the suggestions. Due to our project scope we have very specific guidelines to follow that help determine things such as time step, momentum equations, etc. We have been running models for 2 months now with all the same settings and have never had any problems. Good news though! I found the issue. I input an excess precipitation hyetograph into RAS using a 15-minute time step, encompassing a total of 293 data points. The issue arose because I accidentally had a single of the time slots empty (i.e. instead of a zero value there was no value at all). This caused the back-end equations in RAS to fail and cut out my inflow hydrograph for the same time period in which it then started up normal again for the next time step. Simple solution, however, very annoying that RAS didn't catch this and spit out some sort of runtime error.
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Re: 2D Simulation - Error in Computation Log File

Mohsin
I need some help regarding adding the precipitation in the HEC-RAS.

1- What does the actual mean of time series of precipitation? Is it mean the accumulated rainfall?
for example

Date                                 Simulation time                             Precipitation (mm)
11-01-2019 07:00                   00:00                                               30
11-01-2019 08:00                   01:00                                               30
11-01-2019 09:00                   02:00                                               30

Does it mean the total rainfall added on the 2D flow area during the whole simulation time is 90 mm? Please elaborate?

Thanks