helppyFormex - Support: sr #109149, CFD defining the farfield/domain...


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

Submitted by:  Klaus Burkart <klausb>
Submitted on:  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
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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>
Project Administrator
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
X = read_naca('naca0015.dat')
C = PolyLine(X,closed=True)

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

# 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.))

Klaus Burkart <klausb>


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


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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2016-09-20 klausb Attached File- => Added o-mesh.png, #38568
        Attached File- => Added chord_farfield_domain_radius_2.png, #38569

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