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sam_p

Combined rainfall and hydrograph inflow

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Hi, 

 

I have run a 2D only model with combined rainfall and hydrograph inflow and I'm getting a higher peak outflow (1003 m3/s) than a peak inflow (851 m3/s). When looking at the Qo value at the stated time of peak outflow, it is only 753 m3/s. I was wondering if this may be because the rainfall loss is not included in the Qo column calculation but is reported in the peak outflow?

 

Additionally I can't find an explanation of the Mx column represents on the output file?

 

Any help would be much appreciated.

 

Cheers

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You will find the informations regarding Mx in the 2012-06-AE release notes, but the relevant section is here:

 

"At the end of each line three numbers are displayed after “Mx”. The first two
numbers are the percentage of 1D nodes and percentage of 2D cells that reached a new maximum in
the last computational timestep. The third number is the time in decimal hours since no new
maximum was recorded anywhere within the model. For example, “Mx 10 21 0.0” indicates that 10%
of 1D nodes and 21% of 2D cells recorded a new maximum last timestep, and the time since the last
recorded maximum is zero as would be expected. Once all 1D nodes and 2D cells have reached their
maximums the third (time) value will increase above zero."
 
As far as your Qo difference, I'd be interested to know where you are reading the two different figures from?  If it is in the summary section of the TLF then I would have expected them to include both rainfall and hydrograph outflows.

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Thanks cjh,

 

That's a great help! I did check the release notes and it seems I had an old copy of the 2012-05 notes that didn't include AE.

 

The two different figures come from the peak outflow at a given time step (1003 m3/s) reported in the tlf at the end of the run. And the reported outflow at the given peak time step (753 m3/s) also in the tlf, when scrolling up to look at each time step output.

 

Cheers

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Hi Sam,

 

The discrepancy between the peak inflow an peak outflow could be due to a number of reasons:

  • Tidal component in the Qo values, what type of outflow boundary to you have?
  • There could be an oscillation in the vicinity of the downstream boundary.  This can happen, if a water level boundary is not perpendicular to flow direction.  See here: http://www.tuflow.com/forum//index.php?showtopic=845&st=0&p=2197&#entry2197. Do the velocity directions look at the the downstream boundary?  This issue usually causes the Qo value to oscillate.

Phil

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