air flow #s ?

Adger Smith · 07-14-2013, 02:46 PM

Wow! Someone finally brought it up.. Thanks Dwight.... Fall fronts are different from Spring fronts. You may have the same DA's, but you can get the same DA's with a totally different set of air/weather readings. If the program is not set up(written) to allow for this, you will see variations in the final #'s. That is just one of those things as well as the human element that keeps numbers from repeating exactly or being exactly the same. Then I might add the computer differences. Not all the same Algorithms are used to do the different programs used for correction. Small differences are there yet the Laws of Physics are not cheated and are still in place.

SSDiv6 · 07-14-2013, 04:08 PM

Quote:

Originally Posted by Adger Smith

Wow! Someone finally brought it up.. Thanks Dwight.... Fall fronts are different from Spring fronts. You may have the same DA's, but you can get the same DA's with a totally different set of air/weather readings. If the program is not set up(written) to allow for this, you will see variations in the final #'s. That is just one of those things as well as the human element that keeps numbers from repeating exactly or being exactly the same. Then I might add the computer differences. Not all the same Algorithms are used to do the different programs used for correction. Small differences are there yet the Laws of Physics are not cheated and are still in place.

Yep; there is a lot involved to get the right numbers and it can get a bit complex many times when you start to apply CFD concepts.

Just attended a class on Computational Fluid Dynamics (CFD) sponsored by NASA and it confirms the many things that can affect flow numbers.
Had an interesting discussion with the instructor on how temperatures can effect the final numbers and behavior. Also discussed the importance about velocity and its effects on obtaining real CFM numbers..

Adger Smith · 07-14-2013, 05:27 PM

spSS6 I was going to say that NASA was probably the only group that really get it and do it right. The real problem is we (the avg guy) can't afford to buy the resources they have. We have to use the systems/programs made available to us at the affordable price. (And some not so affordable)
In a perfect world what Kevin is saying could and should happen, but we don't live in that kind of world. I'm not saying everthing is wrong. I am saying there are those among us that try to make things (corrected numbers) closer to right or as close to right as they can be. Then there are others (salesmen that usually don't understand) that use the numbers just for a sales pitch. I'm sure it's tough to be a customer and wade through all of it.

BTY: There are two books I keep on my headboard for those non sleeping late night reads.
Books from my college Fluid Dynamics & Applied Physics

SSDiv6 · 07-14-2013, 06:39 PM

Quote:

Originally Posted by Adger Smith

spSS6 I was going to say that NASA was probably the only group that really get it and do it right. The real problem is we (the avg guy) can't afford to buy the resources they have. We have to use the systems/programs made available to us at the affordable price. (And some not so affordable)
In a perfect world what Kevin is saying could and should happen, but we don't live in that kind of world. I'm not saying everthing is wrong. I am saying there are those among us that try to make things (corrected numbers) closer to right or as close to right as they can be. Then there are others (salesmen that usually don't understand) that use the numbers just for a sales pitch. I'm sure it's tough to be a customer and wade through all of it.

BTY: There are two books I keep on my headboard for those non sleeping late night reads.
Books from my college Fluid Dynamics & Applied Physics

Adger,
NASA has these CFD seminars for free on the web several times a year.
They are called "Webinars" and they are taught by a company named COMSOL and sponsored by NASA.
Next time I get an invite to attend another CFD Webinar, I will post it here so anyone interested can sign up and attend...and it is free.

Adger Smith · 07-14-2013, 06:55 PM

Great! Thanks. Nice to know that . I'll never be too old to learn!

Adger Smith · 07-14-2013, 07:07 PM

Gosh, Those guys are really into the training, even worldwide..
Did a Google on them. Interesting!! I might have to dig back into my 40 year old College... LOL!

Kevin Panzino · 07-14-2013, 08:17 PM

Absolutely the weather correction is key. But correcting simply for density will get you 97% there. Yes, there are small differences. But there should not ever be large differences if both flowbenches are quality pieces, calibrated and properly operated. Of course you will see small variations... But a while ago, there was a dicussion that so and so's flowbench reads 275 CFM, while some other guy's reads 250 Cfm, both at 28"... THat is just plain garbage data there... One of them (or both, with one higg and one low) is clearly WAY off.......

And Yes, NASA, Boeing, Airbus, and any steam turbine/gas turbine manfuacturer gets it, and does it right, thats for sure.

And regardless of the density, the square law is... well a LAW

(sorry, had to get that in one last time

)

Good conversation, gents.

PS: Adger, I have the same sort of books on my nightsand too... My wife thinks Im nuts... She says "nothing like a little "light" reading before bed, huh hon ?? " ....

Kevin

07-14-2013, 02:46 PM	#1
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: air flow #s ? Wow! Someone finally brought it up.. Thanks Dwight.... Fall fronts are different from Spring fronts. You may have the same DA's, but you can get the same DA's with a totally different set of air/weather readings. If the program is not set up(written) to allow for this, you will see variations in the final #'s. That is just one of those things as well as the human element that keeps numbers from repeating exactly or being exactly the same. Then I might add the computer differences. Not all the same Algorithms are used to do the different programs used for correction. Small differences are there yet the Laws of Physics are not cheated and are still in place. __________________ Adger Smith (Former SS)

07-14-2013, 05:27 PM	#3
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: air flow #s ? spSS6 I was going to say that NASA was probably the only group that really get it and do it right. The real problem is we (the avg guy) can't afford to buy the resources they have. We have to use the systems/programs made available to us at the affordable price. (And some not so affordable) In a perfect world what Kevin is saying could and should happen, but we don't live in that kind of world. I'm not saying everthing is wrong. I am saying there are those among us that try to make things (corrected numbers) closer to right or as close to right as they can be. Then there are others (salesmen that usually don't understand) that use the numbers just for a sales pitch. I'm sure it's tough to be a customer and wade through all of it. BTY: There are two books I keep on my headboard for those non sleeping late night reads. Books from my college Fluid Dynamics & Applied Physics __________________ Adger Smith (Former SS) Last edited by Adger Smith; 07-14-2013 at 05:33 PM. Reason: sp

07-14-2013, 06:55 PM	#5
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: air flow #s ? Great! Thanks. Nice to know that . I'll never be too old to learn! __________________ Adger Smith (Former SS)

07-14-2013, 07:07 PM	#6
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: air flow #s ? Gosh, Those guys are really into the training, even worldwide.. Did a Google on them. Interesting!! I might have to dig back into my 40 year old College... LOL! __________________ Adger Smith (Former SS)

07-14-2013, 08:17 PM	#7
Kevin Panzino Senior Member Join Date: Oct 2002 Location: Pittsburgh Posts: 583 Likes: 304 Liked 778 Times in 142 Posts	Re: air flow #s ? Absolutely the weather correction is key. But correcting simply for density will get you 97% there. Yes, there are small differences. But there should not ever be large differences if both flowbenches are quality pieces, calibrated and properly operated. Of course you will see small variations... But a while ago, there was a dicussion that so and so's flowbench reads 275 CFM, while some other guy's reads 250 Cfm, both at 28"... THat is just plain garbage data there... One of them (or both, with one higg and one low) is clearly WAY off....... And Yes, NASA, Boeing, Airbus, and any steam turbine/gas turbine manfuacturer gets it, and does it right, thats for sure. And regardless of the density, the square law is... well a LAW (sorry, had to get that in one last time ) Good conversation, gents. PS: Adger, I have the same sort of books on my nightsand too... My wife thinks Im nuts... She says "nothing like a little "light" reading before bed, huh hon ?? " .... Kevin