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Bernoilli, His Equation, Air Moving in Pipes and Flight

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ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Thu Sep 20, 2007 4:34 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

This web page gives a nice animated view of Bernoulli's Principle in action.  Also, click on the link at the bottom for a discussion of "How Do Airplane Wings Really Work."

  

 This should settle the debate on if Bernoulli's Principle applies to air moving from a supply tank to an actuator on a wing through a pipe with or without a constriction in the pipe..

  

 I also think a number of folks stated that the pressure rises in the constriction, it does not....the pressure falls and the velocity of air increases.  From my engineering days, we always said, "big pipe, big pressure." 

  

 As for how a wing works, I never got into all the boundary layer stuff, but it is a complicated thing that hangs on our planes and gives us the gift of flight.  Bernoulli only plays a small part (if at all).  However, it is the easiest way to explain it with out a bunch of mumbo jumbo so the FAA and everybody else continues to promote Bernoulli as the reason our planes fly. 

  

 http://home.earthlink.net/~mmc1919/venturi.html

  

 ENJOY!!!!!!

  

 Craig Winkelmann, CFI

-- 

"The fruit of love is service.  The fruit of services is peace, and peace begins with a smile."  

- Mother Theresa 

  [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Thu Sep 20, 2007 7:46 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

Hi Craig!  



Thanks for the link.  I read it.  Really nice graphics!  Let's skip to

the chase.   



As far as Bernoulli applying to the problem at hand when viewing it as

an expression of the conservation of energy, I agree completely.  



However, the problem being discussed deals with the movement of a piston

that is driven by a compressed gas and therefore I feel is better

described as "System Work".  Work equaling Pressure Delta Volume   The

definition of work becomes W=Fd for a constant force F along a distance

d. Using the definition of pressure: W= F/A (Ad)= P Delta V  The above

assumes a constant pressure source, which obviously we really do not

have, but close enough.  



So what I have been trying to say is that while Bernoulli will indeed

completely describe the varying pressure, flow rates and velocities

through pipes of varying sizes, (I.E. from the tank TO the actuator) it

is not really meant to describe the process of using a compressed gas to

accomplish the job of lifting the landing gear on a YAK-50, which was

what I assumed was being discussed in the original article. Possibly I

assumed incorrectly.  I also earlier was trying to describe how one

determines how much energy is CONTAINED in a compressed gas and once

again said that Bernoulli's laws do not apply. So before anyone differs

with what I said (as in right, wrong, indifferent   make sure we are

all clear on what I was trying to say to begin with.  The fault again

possibly being my own for not being clear enough. I make that mistake

ALL the time by the way.     



I guess in the end it is a matter of semantics as in order to use the

System Work law you still have to compute end state P and V after all

the line size changes, and what should have been obvious to begin with

is the size of the flow restrictor that is inserted right at the

actuator..... It really being one of the the main determinants anyway

since it is smaller than any line in the system to begin with, probably

including the new line that Tim installed.  It also lends a

visualization of how small the constriction would have to be to cause

Tim's problem assuming no leaks.  



One thing though... For Bernoulli's Principle to apply, the fluid is

assumed to have the same density everywhere (it is "incompressible" like

water.  



Does the compressed air in our systems meet this definition?  Yes, no?

Just curious how you would view the answer to that question Craig.  



Thanks for pointing out an excellent web site.  



Mark Bitterlich 

N50YK

--

brian-1927(at)lloyd.com
Guest

Posted: Fri Sep 21, 2007 9:04 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

On Sep 20, 2007, at 8:45 PM, Bitterlich, Mark G CIV Det Cherry Point,  

MALS-14 64E wrote:



 	  Quote: 	
		   One thing though... For Bernoulli's Principle to apply, the fluid is

 assumed to have the same density everywhere (it is "incompressible"  

 like

 water.



 Does the compressed air in our systems meet this definition?  Yes, no?


	


No. We are clearly dealing with a compressible fluid as the pressure  

on either side of the restriction is different.



We *were* talking about a pipe with an unintended restriction that  

causes a large pressure drop between the storage tank and the rest of  

the system.



--

Brian Lloyd                         3191 Western Drive

brian HYPHEN 1927 AT lloyd DOT com    Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

Ernie

Joined: 11 Jan 2006
Posts: 513

Posted: Sat Sep 22, 2007 5:55 am Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

Magnus has no effect on the burrple destrofunkenspicthen, when bernouli tickles his testicular nipplefricker. Now on the other hand, if you diassemble the pooter evector during a combined molecular fusion butterjamtoastgotshitonmyshirt event, then you may ripp the goddam wings off of the plane.



Ernie

HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sat Sep 22, 2007 10:37 am Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

 	  Ernie wrote: 	
		  Magnus has no effect on the burrple destrofunkenspicthen, when bernouli tickles his testicular nipplefricker. Now on the other hand, if you diassemble the pooter evector during a combined molecular fusion butterjamtoastgotshitonmyshirt event, then you may ripp the goddam wings off of the plane.



Ernie 	




Exactly.....



(The new spell checker went nuts on this)

HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sat Sep 22, 2007 10:38 am Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

 	  Ernie wrote: 	
		  Magnus has no effect on the burrple destrofunkenspicthen, when bernouli tickles his testicular nipplefricker. Now on the other hand, if you diassemble the pooter evector during a combined molecular fusion butterjamtoastgotshitonmyshirt event, then you may ripp the goddam wings off of the plane.



Ernie 	




Exactly.....



(The new spell checker went nuts on this)

HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sat Sep 22, 2007 10:53 am Post subject: More observations.....from the MF'ing air system.

I spoke to the mechanic who did the work on my airplane. Before anyone jumps on him for "shoulda known better", the guy does amazing work and the use of the a smaller diameter line was talked about. His lack of experience with Yaks and my...hmmm...lack of thorough knowledge lead us towards using the fill line from the fill port instead of running a new line from the new bottle (behind my seat). So, we will replace the line with one of original diameter. We will also check for leaks....



Sooo......a few observations from todays flight and something that may add a wrench to the works...OR....turn a light bulb on for someone. 



Go to the airplane to fly this morning. Gauge reads about 40. Turn on the main valve, pressure drops to about 20. Hmmmm...small leak somewhere downstream of the bottle? (The airplane has been sitting for about a week or so)  She starts perfectly after a few blades, I let her warm up to 120c+ and when I push the lever forward, I have about 40 ATM. This is after about 6 or 7 minutes from start to throttle up for take off. Making good pressure. Lift off, gear handle up, that big pressure drop (20+ atm) but gears comes home nicely with a reassuring thump. Pressure rebuilds to >55 ATM after somewhere between 5-10 minutes of flying.  Go flip around a bit, come back into the pattern, gear down off the perch, big pressure drop (same pressure drop) and gear thumps nicely. Land with about 25 atm in the airplane. Run up, pressure builds back up to 40 or so, but did something new this time....hopefully not unsafe.



Brakes on, run up to 70% for about a minute, pressure builds to about 40, then I SHUT OFF (engine still running) the main valve and the pressure builds to about 55 ATM and I shut her down. 



I have some thoughts but want to verify mine with yours....you guys are way smarter than I am. 



I am glad this thread has generated some healthy, yet calm, discussion. I have learned much...

One more question. What are you guys normal oil temps in cruise at a crusie power setting.

yakplt(at)yahoo.com
Guest

Posted: Sat Sep 22, 2007 11:15 am Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

I am starting to wonder whether you might just have a bad gage.  Checked for that yet? 

   

  Mark

  

Tim Gagnon <NiftyYak50(at)fuse.net> wrote:

  [quote]--> Yak-List message posted by: "Tim Gagnon" 



I spoke to the mechanic who did the work on my airplane. Before anyone jumps on him for "shoulda known better", the guy does amazing work and the use of the a smaller diameter line was talked about. His lack of experience with Yaks and my...hmmm...lack of thorough knowledge lead us towards using the fill line from the fill port instead of running a new line from the new bottle (behind my seat). So, we will replace the line with one of original diameter. We will also check for leaks....



Sooo......a few observations from todays flight and something that may add a wrench to the  works...OR....turn a light bulb on for someone. 



Go to the airplane to fly this morning. Gauge reads about 40. Turn on the main valve, pressure drops to about 20. Hmmmm...small leak somewhere downstream of the bottle? (The airplane has been sitting for about a week or so) She starts perfectly after a few blades, I let her warm up to 120c+ and when I push the lever forward, I have about 40 ATM. This is after about 6 or 7 minutes from start to throttle up for take off. Making good pressure. Lift off, gear handle up, that big pressure drop (20+ atm) but gears comes home nicely with a reassuring thump. Pressure rebuilds to >55 ATM after somewhere between 5-10 minutes of flying. Go flip around a bit, come back into the pattern, gear down off the perch, big pressure drop (same pressure drop) and gear thumps nicely. Land with about 25 atm in the airplane. Run up, pressure builds back up to 40 or so, but did something new this time....hopefully not unsafe.



Brakes [quote][b]

HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sat Sep 22, 2007 11:39 am Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

Nope...but I will add that to the list of things to check!

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Sun Sep 23, 2007 6:03 pm Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

Tim:



Is there any possible way for there to be a leak from the main system to the backup/emergency system??  Why would your pressure go UP when you shut off the main system?  What is your emergency air pressure when you start, fly, move gear, etc?



Craig

HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sun Sep 23, 2007 6:30 pm Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

 	  Craig Winkelmann, CFI wrote: 	
		  Tim:



Is there any possible way for there to be a leak from the main system to the backup/emergency system??  Why would your pressure go UP when you shut off the main system?  What is your emergency air pressure when you start, fly, move gear, etc?



Craig 	




Steady at 60. The needle does not move at any time....

jan.mevis(at)informavia.b
Guest

Posted: Sun Sep 23, 2007 11:39 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

Anyway, aerodynamics is a very complex science, and what pilots usually

(have to) know about it, is quite limited. To calculate aerodynamic forces,

you also need the theorem of Blasius and its modern variants for subsonic

speeds. Lots of complex analysis and contour integrals ...



Jan

YK50 RA2005K



--

mark.bitterlich(at)navy.m
Guest

Posted: Mon Sep 24, 2007 10:53 am Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

The pressure goes UP in the main system because when you shut the valve

to the tank on a 50, the compressor is still creating more air pressure,

and will continue to build pressure until the pop-off valve is released.

Thus if you shut off the tank at 40, the gage will continue to show the

pressure increase until the valve pops and releases as per normal

operation.  



The 50 DOES also charge the emergency bottle as well as the main bottle,

unlike the 52.   



--

Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Mon Sep 24, 2007 3:18 pm Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

But is the system only going from 40 to 55atm after the main valve is shut off (and not before)?  If so then it seems there must be a leak somewhere downstream of the main valve.

 	  mark.bitterlich(at)navy.m wrote: 	
		  The pressure goes UP in the main system because when you shut the valve

to the tank on a 50, the compressor is still creating more air pressure,

and will continue to build pressure until the pop-off valve is released.

Thus if you shut off the tank at 40, the gage will continue to show the

pressure increase until the valve pops and releases as per normal

operation.  



The 50 DOES also charge the emergency bottle as well as the main bottle,

unlike the 52.   



--

mark.bitterlich(at)navy.m
Guest

Posted: Mon Sep 24, 2007 4:34 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

Good question//point.  



Yes, if the bottle only fills to 40 and will not fill further, and then

when you close it, the gage goes rather quickly to 50 then your

hypothesis must be correct.   



Mark

--

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Mon Sep 24, 2007 5:35 pm Post subject: Re: Bernoilli, His Equation, Air Moving in Pipes and Flight

My vote is for a downstream leak.  With main off, tank fills to 55 easily.  With main open, in flight, etc, can only get to 40 so compressor is working but can't keep up with the leaking air to get tank to 55.  40 is enough to move gear but excessive loss of pressure is from a leak when you are moving more air through the system by activating the gear (leak plus air needed to move gear).



BTW, Tim says emergency air pressure is rock solid at 60.



Does this make sense to Mark and others?



Craig

viperdoc(at)mindspring.co
Guest

Posted: Mon Sep 24, 2007 6:43 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

Guys,

What makes sense is a set of jacks and a gear retraction test done on those

jacks. Otherwise this is all mental masturbation.

Doc



--

mark.bitterlich(at)navy.m
Guest

Posted: Tue Sep 25, 2007 12:50 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

Tim take note:  Downstream leaks that are not apparent on the deck means

that they are happening only when putting the gear handle up right?

Keep in mind that you can take the landing gear handle on the 50 and

after raising the gear, move it back down to the MIDDLE POSITION.  This

will totally isolate the landing gear from the air system.  After doing

that, take a look at how fast your air gage gains pressure and holds it.

If there is a difference, then there is probably a up side only leak.

This is a much different test than just shutting off your air tank

itself.  EVERY Yak-50 will see a rapid increase in pressure once you

shut off the air tank simply because you are just filling the lines

themselves and not a tank any longer.  I ferried a YAK-50 to California

using this method, so it works... Perfectly. 



ONE WARNING.  You MUST move the handle back to the UP POSITION before

then putting it back to the DOWN position to lower the gear.  If you

fail to do this, the landing gear is going to come down a lot faster

than you've ever seen, and with possible damage.  



Another factor here... In flight once stabilized, if you put the landing

gear handle in the middle and then come back to the UP position and you

lose a bunch of air immediately, this is again an indication of an UP

side leak.  



It is entirely possible to have a one way leak on a YAK-50 actuator.  



Of course, if it were me, that aircraft would have been jacked and

cycled 5 times by now.  What's the hold up?  



Mark

--

jonboede(at)hotmail.com
Guest

Posted: Tue Sep 25, 2007 7:50 pm Post subject: Bernoilli, His Equation, Air Moving in Pipes and Flight

Be it known, Ernie... that your gift for summing things up does not go 

unnoticed or unappreciated.

 	  Quote: 	
		  From: "Ernie" <erniel29(at)gmail.com>

Reply-To: yak-list(at)matronics.com

To: yak-list(at)matronics.com

Subject: Re: Bernoilli, His Equation, Air Moving in Pipes and 

Flight

Date: Sat, 22 Sep 2007 06:55:46 -0700






Magnus has no effect on the burrple destrofunkenspicthen, when bernouli 

tickles his testicular nipplefricker. Now on the other hand, if you 

diassemble the pooter evector during a combined molecular fusion 

butterjamtoastgotshitonmyshirt event, then you may ripp the goddam wings 

off of the plane.



Ernie





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=135747#135747

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