×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Calculating Piped Spillway Capacity

Calculating Piped Spillway Capacity

Calculating Piped Spillway Capacity

(OP)
I am doing a spillway analysis for a small pond/dam.  The spillway is a 24-inch pipe.  I understand how I would calculate the rating curve if it was a short culvert with a known tailwater (or range of tailwater levels).  What if the spillway pipe extends thousands of feet before it gets to an open water body (ditch or something)?  What if the spillway is infinitely long (stays in a pipe forever)?  Can a program like HY-8 handle this kind of situation, or is it only for "short" culverts, and if so, how would you define "short"?  

RE: Calculating Piped Spillway Capacity

KatieTX,

I haven't used HY-8.

Theoretically,
an infinitely long 24 inch diameter pipe, if it is steep and the discharge is below the full flow capacity, will flow partially full. It will have supercritical flow. Any tailwater, in such a case, will have no effect on the flow.
 

RE: Calculating Piped Spillway Capacity

HY8 can't handle complex pipe drain configurations.  It is designed to handle highway culverts.  If your spillway is constructed like a typical culvert with inlet outlet and straight grade in between then HY8 can handle it.  Otherwise, you will need to do it another way.  For high headwater depths such as found in a dam or pond, flow through the spillway is generally under inlet control so that tailwater or pipe length, slope would have no effect on the capacity. For lower flow rates, tailwater may control your capacity.  Analyze your storm drain system separately from the outfall up to the dam (using stormcad or other method) to see if the predicted hydraulic grade line is higher than what HY8 predicts.  

In my opinion, connecting the spillway for a dam directly into  a long storm drain is not advisable.  I would discharge the spillway into a stilling basin and then let it flow into your storm drain system.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources