Coefficient of drag (Cw) in German

Syiad T. Al-Duri

unread,

Feb 3, 2003, 1:18:04 PM2/3/03

to

From: Syiad T. Al-Duri <Syiad....@web.de>

> In some German documents, I'm getting the symbol Cw for the profile
> drag coefficient of an aircraft and I'm not sure about the value it
> gives.

Cw is the drag coefficient. The "W" stands for "Widerstand", which means
resistance in general and drag in this context.

> I often saw this form of the drag equation in German:
>
> Dp = Cw * A * q (A: frontal area)

Was this in the context of aircraft or cars? AFAIR, it is usual to use
the frontal area for cars and the wing area for aircraft.

HTH (at least a bit)
Syiad

--
Live every life as if it were your last!
PGP-key-ID: 78E3F621

Eric Voisard

unread,

Feb 3, 2003, 8:55:05 PM2/3/03

to

From: Eric Voisard <evoi...@ieee.org>

Hi Syiad,

Thanks for your reply.

> > I often saw this form of the drag equation in German:
> >
> > Dp = Cw * A * q (A: frontal area)
>
> Was this in the context of aircraft or cars? AFAIR, it is usual to use
> the frontal area for cars and the wing area for aircraft.

I saw it in the context of aircraft.
In fact, I was wondering if germans (in WW2 context) had the same convention
we are accustomed to: referencing the profile drag coefficient of an
aircraft to its wing area.

Some feedbacks I got seem to indicate it was the case.

(though, the equation above remains useful for specific topics in
aeronautics)

Yours, Eric

Daniel Hofer

unread,

Feb 4, 2003, 2:32:17 PM2/4/03

to

From: Daniel Hofer <joe...@gmx.ch>

> > I often saw this form of the drag equation in German:
> >
> > Dp = Cw * A * q (A: frontal area)
>
> Was this in the context of aircraft or cars? AFAIR, it is usual to
use
> the frontal area for cars and the wing area for aircraft.

I saw it in some books in this way:
Drag: calculated with frontal area
Lift: calculated with wing area

I thought aerodynamics are always the same since 1960 but...it seems
not to be;-)

Daniel

[Moderator: In the automotive world, frontal area is used for CD. In the
aircraft world, wing area (or wetted area) is used, except when talking
about individual components. Then, frontal area is used.]

Don Stauffer

unread,

Feb 5, 2003, 4:29:28 PM2/5/03

to

From: Don Stauffer <stau...@usfamily.net>

Indeed. If we are figuring drag of fuselage itself, frontal area would
be normally used, so figure an auto is same as aircraft fuselage.

Depends a lot on what type of drag. If we are talking parasitic drag,
frontal area is frequently used. Induced drag, say tail surface, then
projected area (as in wing area).

Problem comes in skin friction. As long as people using data know what
was used in reference (test) data, anything proportional to whatever
area used in tests is okay.

--
Don Stauffer in Minnesota
stau...@usfamily.net
webpage- http://www.usfamily.net/web/stauffer

Syiad T. Al-Duri

unread,

Feb 5, 2003, 4:30:33 PM2/5/03

to

From: Syiad T. Al-Duri <Syiad....@web.de>

> I saw it in some books in this way:

> Drag: calculated with frontal area
> Lift: calculated with wing area

Huh!? Then Cl/Cd would not equate L/D. I wouldn't do that; it only
invites confusion.

> I thought aerodynamics are always the same since 1960 but...it seems
> not to be;-)

Judging from my experience, the laws of physics appear to be pretty much
invariable throughout the aeons. ;-)
... but computers have evolved.

Cheers