|
|
| -------------------- |
From:
Kevin
Rodda
Date:
Thu,
Feb 9, 2012
Subject:
Is air a gas or a fluid? |
|
|
| During
my ab initio glider pilot training, I was often told that
"air acts like a fluid" and it was often
suggested to me that I "should imagine air to be an
invisible fluid". |
|
|
| I
found this very helpful at the time ... for example when
visualising speed across the ground (when flying downwind
versus flying upwind at the same indicated air speed) and
also in visualising the flight path across the ground
(when navigating a particular compass heading with
allowance for a cross wind). |
|
|
| In
the former I would imagine myself swimming downstream or
upstream in a rapidly flowing river. |
|
|
| In
the latter I would imagine myself swimming across that
same rapidly flowing river. |
|
|
| My
research today found FLUID defined as a
substance that flows ... but a little more precisely,
in Chemistry, air is classed as a FLUID because it can
take different shapes (if you put it into a jar, it
will fill the jar ... but it can also be compressed). |
|
|
| Air
is therefore probably best viewed (and described) as a
FLUID made up from many different gasses
including visible water vapour. |
|
|
| And
what got me thinking about this again and prompted me
to do some fairly basic cyberspace research
today? |
|
|
| It
was Lindsay Mitchell's reference to "pitot tube" in
relation to the Blanik. |
| |
|
I found that pito tubes are defined as "pressure
measurement instruments used to measure FLUID FLOW
VELOCITY" (for our purposes in gliding to
determine the airspeed of our aircraft). |
|
|
 |
 |
|
|
| Aha
I thought, more proof that air is a FLUID! |
|
|
| Makes
me wonder however why I don't remember even
contemplating that air behaved like a fluid (let alone
that it could actually be a fluid) until speed and/or
direction across the ground versus through the air
became an issue to me in learning to fly. |
|
|
