Science > Physics > Coanda Effect vs. Bernoulli Principle wrt aerodynamic lift
| Topic: |
Science > Physics |
| User: |
"tadchem" |
| Date: |
18 Oct 2007 07:49:35 PM |
| Object: |
Coanda Effect vs. Bernoulli Principle wrt aerodynamic lift |
This YouTube video provides a brief but persuasive demonstration of
the generation of lift by the Coanda Effect rather than the
traditionally accepted explanation invoking Bernoulli:
http://www.youtube.com/watch?v=S-SAQtODAQw
One might expect from the Bernoulli explanation that the amount of
lift generated with the airfoil perpendicular to the airflow would be
negligible.
Not so in fact, as this video shows.
Nevertheless, I expect some will ignore the data and continue to
advocate for Bernoulli.
Tom Davidson
Richmond, VA
.
|
|
| User: "Androcles" |
|
| Title: Re: Coanda Effect vs. Bernoulli Principle wrt aerodynamic lift |
18 Oct 2007 09:42:06 PM |
|
|
"tadchem" <tadchem@comcast.net> wrote in message
news:1192754975.063079.187500@i13g2000prf.googlegroups.com...
: This YouTube video provides a brief but persuasive demonstration of
: the generation of lift by the Coanda Effect rather than the
: traditionally accepted explanation invoking Bernoulli:
: http://www.youtube.com/watch?v=S-SAQtODAQw
:
: One might expect from the Bernoulli explanation that the amount of
: lift generated with the airfoil perpendicular to the airflow would be
: negligible.
:
: Not so in fact, as this video shows.
:
: Nevertheless, I expect some will ignore the data and continue to
: advocate for Bernoulli.
I accept the data.
http://www.youtube.com/watch?v=KCcZyW-6-5o
What's the difference between the Bernoulli explanation and
the Coanda explanation?
Apart from the box-like structure of the wing, decreasing
any airflow beneath it and producing more drag than a
real wing would, what advantage does it have?
Coanda knows how to add drag? Big hairy deal, drag
is expensive.
You know what, Davidson? You are a fuckhead.
Nevertheless, I expect some will ignore the aerodynamics
and continue to advocate for Coanda.
.
|
|
|
|
| User: "Thomas" |
|
| Title: Re: Coanda Effect vs. Bernoulli Principle wrt aerodynamic lift |
19 Oct 2007 06:15:00 AM |
|
|
On 19 Oct, 01:49, tadchem <tadc...@comcast.net> wrote:
This YouTube video provides a brief but persuasive demonstration of
the generation of lift by the Coanda Effect rather than the
traditionally accepted explanation invoking Bernoulli:http://www.youtube.com/watch?v=S-SAQtODAQw
One might expect from the Bernoulli explanation that the amount of
lift generated with the airfoil perpendicular to the airflow would be
negligible.
Not so in fact, as this video shows.
The demonstration is misleading for a number of reasons:
First of all, since the airfoil is fixed at one end, it demonstrates
at best a torque but not an overall lift.
Secondly, the airfoil is not homogeneously exposed to the airstream
but only over a relatively small area. This leads to the viscosity of
the air becoming important here (the stationary air over other regions
of the airfoil is pulled away by the moving air due to friction). For
a spatially homogeneous airstream, the effect should thus not occur
(this is the same as with the well known example of two vertically
hanging sheets of paper being 'attracted' by blowing between them from
the top: if you make the airstream homogeneous for instance by using
just two narrow paper strips (lets say 1 cm wide and 10 cm long) and
blow between them in a controlled way, they do not 'attract' but stay
parallel.
Generally speaking, most effects associated with the Bernoulli
principle (like also the Venturi effect and the Magnus effect) have
nothing to do with the aerodynamic lift, as they appear only due to
the viscosity of the medium (i.e. due the collisions of molecules with
each other). The aerodynamic lift (and drag) on the other hand does in
principle also occur for an ideally inviscid medium.
See my pages http://www.physicsmyths.org.uk/bernoulli.htm and
http://www.physicsmyths.org.uk/drag.htm for more in this respect .
Thomas
.
|
|
|
|
| User: "RP" |
|
| Title: Re: Coanda Effect vs. Bernoulli Principle wrt aerodynamic lift |
19 Oct 2007 12:14:02 AM |
|
|
On Oct 18, 7:49 pm, tadchem <tadc...@comcast.net> wrote:
This YouTube video provides a brief but persuasive demonstration of
the generation of lift by the Coanda Effect rather than the
traditionally accepted explanation invoking Bernoulli:http://www.youtube.=
com/watch?v=3DS-SAQtODAQw
One might expect from the Bernoulli explanation that the amount of
lift generated with the airfoil perpendicular to the airflow would be
negligible.
Not so in fact, as this video shows.
Nevertheless, I expect some will ignore the data and continue to
advocate for Bernoulli.
Tom Davidson
Richmond, VA
I don't see any new effect going on there, and nothing contradictory
to Bernoulli. Look at the opposing torques generated by the two
regions of airflow across the wings surface. Where is the hinge
located wrt these?
The 90=BA air is pushing the wing down, the air moving parallel to it is
pulling it up. The larger surface area and distance from the hinge
allows the pull to overcome the push and the wing rotates up until the
forces balance.
.
|
|
|
|
| User: "Edward Green" |
|
| Title: Re: Coanda Effect vs. Bernoulli Principle wrt aerodynamic lift |
21 Oct 2007 12:12:06 PM |
|
|
On Oct 18, 8:49 pm, tadchem <tadc...@comcast.net> wrote:
This YouTube video provides a brief but persuasive demonstration of
the generation of lift by the Coanda Effect rather than the
traditionally accepted explanation invoking Bernoulli:http://www.youtube.com/watch?v=S-SAQtODAQw
One might expect from the Bernoulli explanation that the amount of
lift generated with the airfoil perpendicular to the airflow would be
negligible.
Not so in fact, as this video shows.
Nevertheless, I expect some will ignore the data and continue to
advocate for Bernoulli.
I can't see the video just now, but in terms of "Coanda vs.
Bernoulli", that seems likely to be something like "Recoil: momentum
conservation or Newton's laws?"
Neither Coanda nor Benoulli are fundamental laws, but consequences of
the fundamental laws applied to fluid flow in various regimes. "Lift"
is simply the Newtonian reaction to deflected airflow, which airflow
could simultaneously include features identified with both names.
.
|
|
|
|
|
Related Articles |
|
|
