×
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

Drag Coefficient
2

Drag Coefficient

Drag Coefficient

(OP)
Does anyone know what the drag coefficient is for an aluminum flag pole?  I am trying to do an analysis with a 90 mph wind speed.

RE: Drag Coefficient

sfinlayson,

If you have access to "EIA/TIA-222-F or G" Standard, there are tables for drag coeff. for round  and octagonal monopoles.
In Canada, S37-01 is followed instead of EIA/TIA standard and also has the same tables.

In NBCC-95 Commentary Fig. B-18 can be used to get the wind pressure without going thru calculation of drag coeff.

Hope this helps.

Lokstr

RE: Drag Coefficient

(OP)
Thanks.  I don't have access to that standard.  I know it is located in AASHTO Standard Specifications of Highway Signs, Luminaires, and Traffic Signals, but I don't have access to that manual either.

RE: Drag Coefficient

If you have access to AASHTO for design of luminaires, I am pretty certain you will find it in there.  I don't think it is specific to aluminum, but you really just need it for a round pole, correct?  
It is in Section 3.8.6 in the 2001 AASHTO code for signs, luminaires, and something else.  They give equations for different shapes, but I didn't see anything about materials.  I don't think it will matter, though.

RE: Drag Coefficient

You can use a coeff. of 1.2 for drag for your pole. It doesn't matter what material it is made up of.

RE: Drag Coefficient

Don't forget the load induced by wind on the flag.  This is how the Australian standard for wind loads, AS 1170.2, calculates the aerodynamic shape factor for free flags, including dynamic effects from flutter:

Cfig = 0.05 + 0.7 * [mf / (ρair*c)] * (Aref / c2)-1.25

where
   Cfig = aerodynamic shape factor (dimensionless)
   mf = unit mass of flag (kilograms per square metre)
   ρair = density of air (1.2 kilograms per cubic metre)
   c = height of flag (metres)
   lf = length of flag (metres)
   Aref = area of flag (square metres)
      for a rectangular flag, Aref = c * lf
      for a pennant flag, Aref = 0.5 * c * lf

The design wind pressure is then:

p = 0.5 * ρair * Vdes2 * Cfig

where:
   p = design wind pressure (pascals, 1 Pa ≅ 0.02 psf)
   ρair = density of air (1.2 kilograms per cubic metre)
   Vdes = design wind speed (metres per second)
   Cfig = aerodynamic shape factor (dimensionless)

RE: Drag Coefficient

Further to my post yesterday, note that the aerodynamic shape factor, Cfig, has a maximum value of 0.76.

RE: Drag Coefficient

Buy the ANSI/NAAMM FP1001 "Guide Specifications for Design of Metal Flagpoles"  It has a sample calculation of an aluminum pole.

https://www.naamm.org/items.aspx

It's $25 and you also get another manual.  You will need to know the size of the flag and what's it is made of.

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