2D model, Flow time series extract method

[Anonymous]

I just wondering which is the method do you use for flow time serie extraction, in a pure 2D model. Do you simply use a profile line, and extract a line over it? In this case Hec-Ras intersect the profile line with the 2D area to find the collection of 2D faces that most closely matches the profile line.
Or, do you use a break line in the exact position of the profile line, in order to get a flow measure over a straight line?

In my opinion the second method is better, but you have to know where to draw the profile line before the simulation running.

I did some attempts, and in my opinion the difference between the two methods is not huge. What do you think about it?

[Anonymous]

I do both. But areas of importance i use a breakline and put a dummy weir on it with a low weir coefficient to evaluate the circumstances at that portion of the 2D model. That coefficient is very important, especially if its going to be fully submerged.

[Anonymous]

Thanks Luis. In your experience, the error – or the difference – between the two methods is huge or negligible?

[Anonymous]

I have not compared. As long as you understand one is utilizing the weir equation or each face of each cell it crosses and the other is method is extracting data directly from the cross sectional face from the output at the time step specified. I have no testing on differences but i do understand the way it is calculated is different and with that understanding i proceed with approaching my model accordingly

[Anonymous]

Thank you for sharing your experience.

[Kazi]

Hi,

Can you please elaborate on how to extract time series data on a pure Hec-RAS 2D model? Please consider that I’m fairly new to Hec-RAS That’d be a great help.

[Anonymous]

Regarding the earlier comment, if you create a dummy structure using the terrain for the weir elevation, it would be better to use the 2D equation domain instead of 1D weir flow.

As far as just getting flow, I would think drawing a profile flow line would be enough.

[Author]

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