Culverts - Open Channel

[renee04]

I'm designing a culvert for the first time. All the material I've read on culverts says that I have to decide whether it has inlet or outlet control. Neither the inlet or outlet are submerged. Won't I just consider this an open channel design instead of a culvert?

Thanks for any advice.

 

[gbam]

Well, it depends, Typically there is a constriction at a culvert that will induce a higher headwater than that of the channel. If the culvert is under outlet control that means that the losses of the culvert added to the tailwater give a higher energy elevation at the upstream end than that of the inlet control. I would suggest that you look at FHWA's HDS-5 for insight into culvet analysis. Also if you are in a channel both up & down stream you may want to analyzed the system with HEC-2/RAS.

Good Luck & have fun

 

[semo]

Here is a good place to start. It is the "Hydraulic Design of Highway Culverts", FHWA Hydraulic Design Series No. 5 as GBAM recommended. It outlines the calculations for culvert design and includes charts needed for most all culverts.

http://www.polytechnic.edu.na/Schools/civil/Libraries/Hydraulics/hds5SI.pdf

 

[Maury]

Start by determing the flow depth at the downstream end of the culvert, then calculate for both cases, inlet and outlet control. The FHWA publication suggested by Semo will show you how to do this and how to determine which control applies. (It's a free download so just print it out). The inlet and outlet head losses ar to great to ignore, so don't try to treat the culvert as a simple open channel.