Contact US

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!

*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

Hydraulic grade line

Hydraulic grade line

Hydraulic grade line

If you have the Req'd flow Q, diam. D, Length L, manning's "n", and entrance loss Ke, for each pipe length, than you can calc. the head losses thru the pipe.  he=Ke*V^2/2g; hf=29*n^2*L/[(D/4)^1.333]; hv=V^2/2g where he, hf, hv are the entrance, friction, and veloc. heads.  The req'd head to push the flow thru the pipe = the head losses.  Any hv gained thru the pipe sys. is lost at the end of the pipe system.  By starting at the downstream water elevations and by adding the losses as we go upsteam we can plot the hydraulic grade line(HGL).  This can all be done on a spreadsheet.  My question is:  Do we need to include entrance losses at each Catch basin.  The flow appears to be passing thru the CB with very little loss of speed.  It's unlike the entrance to a culvert where the flow goes from zero velocity to pipe flow velocity.

RE: Hydraulic grade line

FHWA has put out a document "Hydraulic Engineering Circular 22" that has a methodology to calculate the head loss through access holes, ie CBs.  I would recommend obtaining that document from their website, http://www.fhwa.dot.gov/engineering/hydraulics/library_listing.cfm.  This approach uses a series of coefficients to obtain the single coefficient for the structure.  It is a bear to go through by hand but one can code a spreadsheet to ease the calculations.  Storm Cad and other computer programs have this methodology built into them as well.


RE: Hydraulic grade line

yes, you should add a loss to account for flow contraction,  suggest K = .05.  Actually, under higher flows it is very similar to a culvert as you probably will have ponded water in your catch basin with velocity = zero.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close