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!

*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.

Jobs

How to calculate Wind Loading on a Rectangular Antenna

How to calculate Wind Loading on a Rectangular Antenna

(OP)
I need to calculate the wind-loading force (lbf or N) that will be applied to my rectangular antenna enclosure (face area of 2.6 sq ft /0.24 sq m) in a wind speed of 60mph (97km/h). The estimated drag coefficient (based on a flat face with rounded edges) is 1.9.
Can someone provide me with the correct formula to use, or point me in a direction to solving this?
Thank you,
Solsurfer1
 

RE: How to calculate Wind Loading on a Rectangular Antenna

F = (Cd)(Area)(0.5)(rho)(V^2)

...oh, and don't double-post.   

RE: How to calculate Wind Loading on a Rectangular Antenna

(OP)
Thank you btrueblood for both the equation and the forum policy; I appreciate it.
 

RE: How to calculate Wind Loading on a Rectangular Antenna

that is the drag load ... you might consider the antenna as a lifting surface, Cl instead of Cd and acting in the normal direction ... assume a few degress of sideslip (creating AoA for the antenna).  

you might also want to consider a "ground handling" load, something like 200 lbs.

RE: How to calculate Wind Loading on a Rectangular Antenna

(OP)
rb1957,
Can you elaborate? My apologies, but I don't quite understand; too many years in another field has evaporated my aerodynamics studies.

RE: How to calculate Wind Loading on a Rectangular Antenna

drag load on an antenna tends to be very small.

you could imagine the antenna (i'm assuming a "large" VHF type of blade antenna) could work like a small lifting surface (generating lift) ... a bigger load, working the attachments and the supporting structure somewhat more, but still typically not very large.

in my experience, if you assume a ground handling load of 200 lbs acting normal to the blade (torquing the attachments) you exercise the attachments a reasonable amount and this causes you to add a reasonable amount of structure to support the antenna so it almost certainly (never in my experimence) never vibrates.  typically you'll need a U-channel to support the antenna, clips to attach to adjacent frames and a dblr to hide the rivet CSKs.  

and a damage tolerance analysis to define the new inspection program.

RE: How to calculate Wind Loading on a Rectangular Antenna

seeing your dbl post ... is the antenna on a plane or a building ?

RE: How to calculate Wind Loading on a Rectangular Antenna

(OP)
rb1957,
Sorry about the dbl post...wont happen again.
The antenna is mounted to a tower or pole. I'm trying to understand what the wind load on my antenna will have on its mounts and the tower/pole interface.

RE: How to calculate Wind Loading on a Rectangular Antenna

i think you'll get wind speeds from the building codes.  maybe they give you force as well ... i'd expect that they'd define so many psi rather than a wind speed of so many fps.  so then it'd be just p*A

RE: How to calculate Wind Loading on a Rectangular Antenna

Just use the drag tables from Hoerner's drag book titled "Fluid Dynamic Drag" from 1958, that will do.

Neglecting deflection (preventing that you have to calculate eventual "lift") will be conservative and realistic.

RE: How to calculate Wind Loading on a Rectangular Antenna

Draw a CAD model, then model it in a finite element software capable of solving the Navier Stokes equations.
This will then verify your empirical calcs.  

peace
Fe

RE: How to calculate Wind Loading on a Rectangular Antenna

@FeX32

No, this will verify your Navier-Stokes solver, not your empirical model. In stalled flow, it's more a coincidence than wisdom if your CFD coincides with measurements.

CFD is not able to predict this in general, the solution is strongly dependent on the turbulence model you use. Even though some companies tuned their solvers endlessly, and their results will be reasonable, you can never, and should never, use CFD in general for these purposes (unless you're doing DNS or so which is still unfeasible nowadays).

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


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