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FES's Effiency

FES's Effiency

FES's Effiency

I have a  two part question concerning concrete flared end sections.
1)  Does a flared end section increase "inlet control" intake?
and if so,
2)  Does anyone know where I can find, either formula's for calculating a fes's inlet control capacity or a set of nomographs with which to accomplish the same goal.

RE: FES's Effiency

As far as I know, an outlet flared end section has no effect on inlet losses.  It can only have a small effect on outlet head loss.  If used at the inlet it may have a small effect.  You should be able to get data from the flared end section manufacturer or from your State DOT.

good luck

RE: FES's Effiency

According to the FHWA's HDS-5 (2001), Table 12 in Appendix A, β€œβ€˜End Sections conforming to fill slope,’ made of either metal or concrete, are the sections commonly available from manufacturers. From limited tests they are equivalent in operation to a headwall in both inlet and outlet control. Some end sections, incorporating a closed taper in their design have a superior hydraulic performance. These latter sections can be designed using the information given for the beveled inlet.”

Keep in mind that these empirical equations used to calculate headwater are only +/-10% accuracy.


RE: FES's Effiency

HECRAS Hydraulic Ref, Tables 6.3 and 6.4 give entrance loss coefficients, per the degree of taper and shape of opening.  I believe those are per HDS5, but maybe not.  In any case, they are typical and widely accepted in the USA.  These are factored into the headloss through the structure, and will give you sufficient answers to both your questions.  HECRAS software and manuals are free domain, from the USACOE here:

Engineering is the practice of the art of science - Steve

RE: FES's Effiency

Thanks for the direction.  The engineer who reviews plans for a city I work in has recently required that all culverts be able to accomodate the 100-year storm without overflowing into the street.  As a result I wanted to make sure that I was getting every bit of effiency out of the culvert as possible to avoid lowering the culvert too far beneath the roadway.  Thanks again.

RE: FES's Effiency

Just noticing cveg05's last statement about "...the engineer has recently required..." that raised my hackles a bit.  I am of the opinion that the engineer can only REQUIRE what the code / ordinance requires.  This may be a whole separate topic.  I have seen our state DEQ "require" items that they had no authority doing so.

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