The Impossibility of Flying Heavy Aircraft Without Training

Most aerodynamic equations dealing with low subsonic speeds treat air as an
incompressible fluid because compressibility doesn't have a significant
effect until you approach sonic speeds.

Isn't compressiblity what causes pressure changes (absent temperature
changes)?

Jose
--
Money: what you need when you run out of brains.
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Jose wrote:
Most aerodynamic equations dealing with low subsonic speeds treat air as an
incompressible fluid because compressibility doesn't have a significant
effect until you approach sonic speeds.

Isn't compressiblity what causes pressure changes (absent temperature
changes)?


No.

Compressible fluids (commonly called liquids) also experience
pressure changes. THis is used advantageously for hydraulic
power.

The distinction is that a compressible fluid (commonly called gas)
undergoes a volume change proportionate to the pressure change,
while the volume of an incompressible fluid changes little with
pressure. Compressible fluids obey Charles' law,
(or is it Boyle's law?):

P1 * V2 = P2 * V1

--

FF

The distinction is that a compressible fluid (commonly called gas)
undergoes a volume change proportionate to the pressure change

Well, when an object passes through the air, does it not compress the
air in front of it (and rarefy the air behind it)? This is how speakers
work. Those are all pressure changes.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

"Jose" wrote

Well, when an object passes through the air, does it not compress the
air in front of it (and rarefy the air behind it)? This is how speakers
work. Those are all pressure changes.

Air is pressurized behind the speaker, just as well as the air in front of
it. That is how bass reflex speakers work.
--
Jim in NC

Air is pressurized behind the speaker, just as well as the air in front of
it. That is how bass reflex speakers work.

Yes, but out of phase. Air is pressurized in the direction the speaker
cone is moving. It goes back and forth.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.