Head Water Over Depth Ratio
Head Water Over Depth Ratio
(OP)
I was wondering if anyone out there knows why we use a headwater over depth ratio of 1.5 as a check in the design of cross drains? Why 1.5? Is it a pressure thing?
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Head Water Over Depth Ratio
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RE: Head Water Over Depth Ratio
Inlet flow control in horizontally-aligned orifices changes from weir-type to orifice-type flow at around HW=0.4D. Since orifice flow is more restrictive, maybe it is an arbitrary height at which to rerun the numbers in case the analysis to this point has only considered weir flow.
This would be quite arbitrary indeed for verticle inlet alignments, which are usually considered to be limited to orifice flow at HW=D.
RE: Head Water Over Depth Ratio
RE: Head Water Over Depth Ratio
for HW/d ratios over 1.5. It would be great to get someone elses interpretation on this. You can download Hec 10 at the link below. The section I am referring to begins on page 87.
http://www.fhwa.dot.gov/bridge/hec10.pdf