×
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

colebrooks equation
8

colebrooks equation

colebrooks equation

(OP)
Guys,

This is peanuts for you folks here. Won't take much of your valuable time.

Calculating pressure drops in pipeline, as I understand, needs first, an estimation of friction factor. I have referred to some books, and almost all of them gave me the following.

                               
1/sqrt(f)   = -2 x log10 [(e/ 3.7D)+ (2.51/Re sqrt(f))]

I learned that this was formulated in 1945. My question is, Is there any other type of colebrook equation, which is more recent or more accurate. Is the above one the current one?

(Is this really a stupid question, like asking if there is a better versin of ohms law or newtons third law of motion?)

thanks in advance

dinesh

RE: colebrooks equation

2
There is:
1/sqrt(f)  = -2 log10 [(e/ 3.7D)+ (2.51/(Re sqrt(f)))]
(the one you quote)

1/sqrt(f)  = 1.74 -2 log10 [(2 e/D)+ (18.7/(Re sqrt(f)))]

1/sqrt(f)= 1.14+2log10(D/e)-2log10[1+(9.3/(Re e/D sqrt(f))]

www.cheresources.com give the three above and compares

RE: colebrooks equation



more accurate?

these are empirical equations based on specific piping and flow testing, usually in water.

RE: colebrooks equation

siretb /quark / Guidoo:

You guys should be recognized for the direct, succinct, and valuable contribution to FreeFall's request.  This series of articles goes to the grain of dealing with an out-dated, implicit equation and offers practical, up-dated explicit solutions that can be directly employed by engineers in their own programs or spreadsheets for quick and accurate fluid flow solutions.  You guys have not only helped FreeFall, but you've assisted countless others who will read this thread.  Kudos to you all.

Art Montemayor
Spring, TX

RE: colebrooks equation

I think the actual answer to the question is that the Colebrook equation is still the best equation and that nothing has come along to replace it yet.   There are explicit equations that are approximations (even to a high degree) of the Colebrook equation, but the Colebrook equation is still the "gold" standard.



RE: colebrooks equation

(OP)
Guys,

Thank you so much for ur clarifications. It really helped me.

Wishing you all a great 2005 ahead.

Dinesh

RE: colebrooks equation

There actually has been quite a bit of work going on in the pipeline industry regarding the transmission factor equations.  Most notable is the GERG equation, which improves the Colebrook-White combined law model by correctly incorporating an efficiency factor and by providing an “n” parameter which controls the rate of transition. The rate of transition was identified as early as 1956 by the natural gas industry as being the main problem with the Colebrook-White equation.

Dr. Zaragola’s experiments with the Princeton University super pipe have redefined Prandlt’s smooth pipe law.  The partially turbulent flow portion of the GERG equation conforms to the Zaragola equation.

For more info, see the papers below:

http://www.psig.org/Papers/archive.asp?year=2002&submit=Retrieve+Papers

Paper 0202 - Taking the Rough With The Smooth – A New Look At Transmission-Factor Formulae

http://www.psig.org/Papers/archive.asp?year=2001&submit=Retrieve+Papers

Paper 0112 - A Tutorial on Pipe Flow Equations


RE: colebrooks equation

Nice link.

Regards,

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