Coefficient of drag for Rectangular Hollow Sections
Coefficient of drag for Rectangular Hollow Sections
(OP)
Does anyone know where I can find Coefficient of Drag for typical SHS and RHS sections. I have data for a square edge prism and a large rounded corner but not for corner radii typical of square and rectangular steel hollow sections.






RE: Coefficient of drag for Rectangular Hollow Sections
RE: Coefficient of drag for Rectangular Hollow Sections
RE: Coefficient of drag for Rectangular Hollow Sections
I wonder if that is close and what about an RHS.
RE: Coefficient of drag for Rectangular Hollow Sections
But surely the difference between 1.2 and 2.2 is not in the big scheme of things?
RE: Coefficient of drag for Rectangular Hollow Sections
For an aspect ratio of 2:1, I calculate a Cd of 2.78/1.6 depending on wind direction.
Regards Jake
RE: Coefficient of drag for Rectangular Hollow Sections
RE: Coefficient of drag for Rectangular Hollow Sections
An excerpt from same is shown here, and may answer your question:
http://www.boatdesign.net/forums/attachments/hydro...
Though the result is pretty dependent on Reynold's number based on this:
http://www.fgg.uni-lj.si/~/pmoze/ESDEP/master/wg13...
RE: Coefficient of drag for Rectangular Hollow Sections
btrueblood, useful information. From what I have seen a useable approximation is
r/b
This ignores reduction that can occur due to Reynold's number.
In my case for r/b=0.13 I get Cd=1.7 which is a useful saving over a sharp corner at Cd=2.2
RE: Coefficient of drag for Rectangular Hollow Sections
https://law.resource.org/pub/eur/ibr/en.1991.1.4.2...
RE: Coefficient of drag for Rectangular Hollow Sections
RE: Coefficient of drag for Rectangular Hollow Sections
If you really want to get technical, drag coefficients are basically characterized by:
1. Flow: Laminar or Turbulent
2. Form: Sharp edged or rounded
3. Longitudinal Length: Long or short
4. Shielding
The first two are intertwined. Sharp edged objects almost always have turbulent flow, rounded objects can be laminar at low fluid velocities (however for structual engineering ultimate wind will be turbulent). A circular (infinitely long) section will have Cd = 1.2 in laminar flow and Cd = 0.4 in turbulent flow when the boundary layer transitions. A long object will always have a high drag coefficient than a short one (out of plane to wind direction), as the fluid can't shed out of plane around the object. Then there's shielding; if the flow has become turbulent or somewhat disturbed before reaching the member in question, ascertaining a drag coefficient other than a conservative guess is futile. Basically it's too complex to waste your time with, and you should increase your beam size if you're concerned.
RE: Coefficient of drag for Rectangular Hollow Sections