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Tuesday, December 8, 2015

Pressure and Weir Flow

Here’s a video of pressure and weir flow yesterday at a bridge near my house.  This was brought on by some very intense rainfall over a short period of time.  What do you think the weir coefficient would be?



‘Tis the season in many parts of the world for heavy rains and high water.  This is a good reminder to always try to get out and view your rivers and streams when they are flooding.  There is nothing like a first-hand view of a flood to understand how water interacts around our infrastructure.  This is invaluable information for setting up and calibrating your HEC-RAS models. 
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6 comments:

  1. WBWLRDecember 8, 2015 at 4:57 PM

    3.0?? Is there a hydraulic jump at the downstream side of the bridge?

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  2. UnknownDecember 10, 2015 at 9:29 AM

    did you happen to measure the velocity or depth? when the water goes down, a crude survey of the elevation drop between the upstream and downstream sides would also be a great value.

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  3. RuminatorDecember 10, 2015 at 12:05 PM

    I'd say between 2.5 and 3.0 for the weir coefficient. The flow looks pretty smooth and I didn't see a lot of impediment to flow over the weir. I'd be hesitant to use anything over 3.0 as well. I know the theoretical value, but that is realized only in the lab, in general. ;)

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