Box Culvert under Outlet Control

I have a problem in a practice test that is asking for the outlet control HW depth at the inlet to a 7 x 5' box culvert.

Q=400 cfs

S= 1.5

TW = 3ft

n = 0.012

Is there an outlet control box nomograph?? I'm not seeing one in HDS 5, or any of my references. I'm stuck on solving this.

This isn't the complete problem, so just a little help getting started would be appreciated. Thanks.

John,

My SoPE notes has a couple nonographs for culverts, but they are both for inlet control.

Do have the CERM? Is it type 4 flow?

how about this from a google image search for "type 4 culvert nomograph":

Thanks, I have this nomograph. I don't think this is what you would use.

I tried, and my answers do not match any of the given.

Hmmm. I check a few of my sources and they didn't have anything different. Did you try to solve it with an equation. It's likely an error in the solution though. I've been finding lots of those.

OK, I think I have it.

I just submitted to the instructor, so I'll let you know how this worked out.

Anyway, Figure 41 in the Concrete Pipe Design Manual, I'm sure this is in HDS 5 as well, I don't have my copy with me.

"HEAD FOR CONCRETE BOX CULVERTS FLOWING FULL"

Solve for 'H' using the nomograph, and if you read the fine print under the diagram:

SUBMERGED OUTLET CULVERT FLOWING FULL:

HW = H + ho - LSo

I'll update the post if this was correct.

Mike

How's this?

If culvert length is not given, can't estimate head losses (assume short length)

V = Q/A = 400/35 = 11.43 fps

____ ________

V = v 2gH = v(2x32.2xH

Head difference H = 2.03 ft

If TW = 3 ft, HW = 3 + 2.03 = 5.03 ft

Thank you for the reply, Dr G.

I left out the Length, which was 200 feet. I was trying to get started on this problem, and not post the entire problem.

I will make a note of your example as well.

So, what's the actual answer? In my solution, I also ignored the discharge coefficient, but for a square edge entrance into a box culvert of significant width:height ratio, the Cd is fairly high (close to 1.0), as far as I know.