Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Swamee & Jain Friction Factor Equation 3

Status
Not open for further replies.
Mech85

Mech85

Mechanical
Joined
Jun 11, 2003
Messages
52
Location
AU
Hello,

The original Swamee & Jain explicit equation for friction factor calculation for turbulent flow in pipes has f = 0.25/[(log.....)]^2.

I have also seen on the web f = 1.325/[(log.....)]^2. The difference is NOT the factor of four beween the Fanning friction factor and the Darcy friction factor. Can anyone explain the discrepancy?
Thanks
 
Sort by date Sort by votes
Hi Perth
never seen the 1.325, but the 0.25 is the one I memorised after checking it against Shacham and Colebrook White with good correlation.
I expect it may be a mistake.

If you are from Perth Australia, you probably got Swamee Jain 0.25 from the Hardie Iplex PE manual. Where did the 1.325 come from?
Cheers

Steve McKenzie
 
Upvote 0 Downvote
To Perth1, may be I'm wrong but it appears that

(ln x)2/(log x)2 = 1.325/0.25= 5.3​

Id est,

(0.25)(ln x)2= (1.325)(log x)2​

Thus, one formula is based on log x, and the other on ln x.

Would I be right ? [pipe]
 
Upvote 0 Downvote
25362,

Yes, you're correct - I have gone back and checked the two articles using 1.325 in the formula and they DO use ln rather than log. Thanks for spotting the difference.
 
Upvote 0 Downvote
That's a brilliant... (Ok, I resisted myself saying it a guess:-)). One star for you.

Regards,


Eng-Tips.com : Solving your problems before you get them.
 
Upvote 0 Downvote
Quark. Thanks for the undeserved star.
"Things should be made as simple as possible, but not any simpler." Albert Einstein
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

SPKR
  • Locked
  • Question Question
Friction loss for Flanged Concentric reducer
Replies
4
Views
3K
TenPenny
TenPenny
jcth
  • Locked
  • Question Question
Centrifugal Pump Suction-Inlet Design & Best Practices
Replies
6
Views
4K
pierreick
pierreick
gyee
  • Locked
  • Question Question
Pump spacing from wall & parallel pumps
Replies
0
Views
568
gyee
gyee
MechEng Dan
  • Locked
  • Question Question
Mech Seal Coolers - ASME B&PVC Sect VIII, Y or N
Replies
1
Views
295
Heaviside1925
Heaviside1925
nishanxavierchammany
  • Locked
  • Question Question
What is the reason for low lube oil pressure in Reciprocating air compressor , Belliss & Morcom
Replies
10
Views
2K
nishanxavierchammany
nishanxavierchammany

Part and Inventory Search

Sponsor

Back
Top