I have looked closely at the page detailing the Coanda effect and would
like to raise a few questions in this forum:
The effect you demonstrate is, as you point out, something that has been
known about since the 1930s`. Your page in fact makes several claims, some
of which seem to be supported by the diagrams etc, others of which seem to
have no supporting data.
1) At its simplest, this effect manifests itself when a fast moving air
stream is passed over an approximately umbrella shaped lightweight object.
The object lifts as there is a pressure differential between the top of the
object and the underside. This is fine and seems obvious.
Question: How is this significantly different from what happens with a
conventional aerofoil placed in a fast moving airstream? I can see that in
effect you demonstrate, the lift is in the direction from which the air
flow comes. In a conventional aerofoil the lift is deemed to be at
(typically) right angles to the air flow. But in what other ways is the
phenomenon sufficiently different to deserve its designation as a different
effect?
In fact, is it really the Coanda effect (where a vertical stream of fluid
will change its path to follow a curved object in its way) or isn`t it
simply the same as a conventional aerofoil - it is merely demonstrating
aerodynamic lift using a different shape of aerofoil......?
In any event, I would like to know how much energy is needed to produce a
given amount of lift.
I strongly suspect that the same degree of lift could be produced by a more
orthodox solution - viz: pointing the jet of air out of the bottom of the
object (i.e. use the airflow as good old fashioned thrust). Despite the
fact that lift is produced by this airstream hitting the object `head on`
it is nontheless to some extent fighting itself in a way that is clearly
not so with a simple thrust-from-the-bottom....
2) My difficulties really come in the paragraph which begins: "The Coanda
effect can also be used in an Electro-HydroDynamics (EHD) device" when you
apply the same principle to demonstrate the lifting of the object using a
high-voltage potential to generate a stream of charged particles which flow
over the object.
You say: "The differential pressure in the medium ( aether) between the
upper surface and the inner surface creates a mechanical force which
propels the device in one direction."
I fail to see how this is basically any different from a lot of traditional
electrostatic demonstrations which show that a stream of charged particles
has mass and, if moving, also momentum - period.
I don`t see how in any whatsoever it justifies the appeal to a pressure
difference in the `aether` or whatever. The only virtue in a stream of air
is that it has mass and moves. The only difference with a stream of
electrostatically charged particles is that it has `less mass` and
therefore you will need `more of it` to produce the same lift.
I notice for example that in the electrostatic version, you have to balence
out most of the weight of the object before you can see the lift whereas
the airstream one needs no counterbalence.
Again you say: "The most interesting thing to notice is that there is a
direct conversion of electrostatic energy into kinetic energy with no
moving parts"
I don`t see how this is any different from the electrostatic pinwheel
demonstrations that are used to show the action of points.
[For those unfamiliar with this aparatus, here is a picture of an
electrostatic pinwheel:
http://buphy.bu.edu/~duffy/elec/5B30_50.html]
In the pinwheel, it is the flow of charged particles away from the points
that creates a turning force. The only difference I can see is that in the
pinwheen the motion is rotary, in your demonstration the movement is vertical.
You then go on to say:
"The motion of the medium around the ship can be used for producing
electrical energy and
self-sustaining the primary effect."
Maybe I missed something here, but I didn`t see any experimental apparatus
to demonstrate:
A. That it is possible to convert the stream of charged particles back into
electricity
B. That this conversion is sufficiently efficient to allow the process to
be self-sustaining or
C. A calculation of how much energy is needed to produce a given degree of
lift.
In regard to the latter, I again strongly suspect that once you have
calculated how much energy is required to produce a given amount of lift
using a stream of charged particles, then you may well get much more lift
applying the same amount of energy to a more conventional lift-producing
apparatus......in other words this may turn out to be an interesting but
essentially miniscule effect with little practical usefulness in
propulsion....
I do genuinely ask these questions in a spirit of enquiry but also with a
mind to maintaining a degree of rigour - I look forward to the ensuing
discussion!
Many thanks and keep up the good work!
I particularly appreciate the way in which you take care to publish clear
working diagrams and experimental data.
Nick Hall
Manchester - UK
------------------------------------------------------
"That which a man cannot afford to lose owns him"
------------------------------------------------------
-------------------------------------------------------------
To leave this list, email <listserver@keelynet.com>
with the body text: leave Interact
list archives and on line subscription forms are at
http://keelynet.com/interact/
-------------------------------------------------------------