More
about the "silly question" that I asked few weeks ago:
I wanted to study by myself if suction alone could produce
lift.
I
have in my bathroom a fan [venta] mounted on the small
ventilation window, that has vertical hinges.
When
the fan is rotating, and the window isn't locked, the fan
pulls open the window.
I
took a piece of cardboard, and attached it 2 c.m behind the
fan's outlet, so the air flows out but it had to change its
flow direction for 90 degrees to radial directions around.
And
really- the window didn't move! My first reaction was- Okay-
here we see Newton's third law- because the air couldn't flow ,
there was no reaction!
But
then rose in me the idea that the force applied by the airflow
against the attached cardboard is playing here an important
role.
I
looked for a way to solve this question, and here it is:
To prove my
idea I tried to use a kitchen scale, I had to hold it
horizontally behind the fan. The airflow's force was about 80
grams.
After
I took the scale, and pushed the window with the scale to
open it.[ the fan wasn't rotating this time] Now showed the
scale 40 grams .Of course, this measure isn't precise, but... Here
I had a good evidence that the airflow's impact on the
attached cardboard is big enough to stop the window's motion.
And now I held the scale touching the window's frame- Close to
the air's inlet. As I operated the fan, the window opened
and pushed the scale with a force of 40 grams!
I
measured the time for the fan to open the window- free
suction and outlet. It took about 3.5 seconds.
Than
I attached the cardboard in front of the fan, so the air
entered from the perimeter, and now the third Newton's law had
a nice show. The window opened only through reaction, without
any suction. This time it took about 5 seconds. It seems that
suction alone can play an important role!
But
I wanted to be sure that the attached cardboard didn't
block the air entrance to the fan, and it proved to be far
enough to allow full air f low.
I
have to emphasize that I can't guaranty for the validity of
the data that I presented here- all what I have done was
with cardboard, adhesive tape, and a kitchen scale hold by
hand.
Maybe
that at higher airflow speed, the ratio suction/thrust will
be different, but since I do not have any variable speed fan,
I can't do more.
Now
the big question:Did I did discover America?
I
googled in order to find some data relating to my findings-
but nothing!
I
would like your comments.