# sr #109149: CFD defining the farfield/domain radius?

 Submitter: Klaus Burkart Submitted: Tue 20 Sep 2016 04:43:34 PM UTC Category: Open discussion Priority: 5 - Normal Severity: 3 - Normal Privacy: Public Assigned to: None Open/Closed: Open Operating System: GNU/Linux
* Mandatory Fields

Comment Type & Canned Response:

## Discussion

Tue 20 Sep 2016 07:01:58 PM UTC, comment #1:

The dsize() of an object is the length of the diagonal of the bounding box (bbox()) of the object.

For a profile as naca0015, the chord would be the x-distance between the extreme points. This is given by C.sizes()[0].

If the profile is not symmetric about the x-axis, it could probably be computed as the distance between the points with the extreme x values?

Benedict Verhegghe <bverheg>
Tue 20 Sep 2016 04:43:34 PM UTC, original submission:

Let's assume, the flow domain is circular, then the domain radius should be 100x the chord of the airfoil.

The chord is the "length" of the airfoil cross section or in other words the distance from the leading edge to the trailing edge (see attached picture).

Looking at the code below, I am not sure whether C.dsize() gives me the chord or the contour length of the PolyLine?

# Object boundary
C = PolyLine(X,closed=True)
draw(C,color=red)

# Outer boundary
sc = 100 # scaling factor / domain radius?
O = circle().scale(sc*C.dsize()).trl(C.center())
draw(O,color=blue)

# Mesh
# n = points along airfoil surface
n = 300
# m = jmax, points from airfoil surface to farfield patch
m = 137
Ca = C.approx(n).toFormex()
Oa = O.approx(n).toFormex()
M = simple.connectCurves(Ca,Oa,mesh.seed(m,2.,0.))
draw(M,color=green)

Klaus Burkart <klausb>

## Attached Files

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:

Comment:

Attached Files
file #38568:  o-mesh.png added by klausb (188KiB - image/png)

## Dependencies

Depends on the following items: None found

Items that depend on this one: None found

Carbon-Copy List
• -email is unavailable- added by bverheg (Posted a comment)
• -email is unavailable- added by klausb (Submitted the item)
•

There are 0 votes so far. Votes easily highlight which items people would like to see resolved in priority, independently of the priority of the item set by tracker managers.

Only logged-in users can vote.