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ESDU Challenge: Cabin Noise in a Gulfstream III

Posted July 18, 2014 12:00 AM by SavvyExacta
Pathfinder Tags: ESDU

In this series from IHS ESDU, challenge questions will be posted for the community. Some questions may require calculations and others are general knowledge questions.

Here's this week's question:

Sub-boundary-layer counter-rotating vortex generators were selected to reduce cabin noise in the Gulfstream III aircraft. The use of co-rotating generators of a similar size would probably:

a) increase the maximum effectiveness and improve downstream persistence

b) decrease the maximum effectiveness and improve downstream persistence

c) increase the maximum effectiveness and decrease downstream persistence

And the answer is:

b) Decrease the maximum effectiveness and improve downstream persistence.

ESDU 93026 gives examples of the practical application of vortex generators to aircraft. ESDU 93024 and ESDU 93025 give guidance on the aerodynamic principles and design of vortex generators for controlling shock-induced separation.

Visit the IHS ESDU website for more information about the validated design methods, or to request a trial subscription.

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Doorman
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#1

Re: ESDU Challenge: Cabin Noise in a Gulfstream III

07/18/2014 11:24 AM

Co-rotating VG should slightly improve the vortex persistence. Even though sub-boundary layer, even 25% of the BL in depth, these can disturb 75% of the BL.

Co-rotating VG should slightly decrease the desired effectiveness. This is a WAG, made because Gulfstream Aerospace selected counter-rotating VG's, and the purpose of the exercise was to decrease cabin noise. This is the trade-off.

So, I'll say the answer is 'B'.

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SolarEagle
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#2

Re: ESDU Challenge: Cabin Noise in a Gulfstream III

07/18/2014 11:25 AM

a....but I guess it depends on the design...

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SolarEagle
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#4
In reply to #2

Re: ESDU Challenge: Cabin Noise in a Gulfstream III

07/19/2014 12:23 AM

I change to c....

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#3

Re: ESDU Challenge: Cabin Noise in a Gulfstream III

07/18/2014 7:57 PM

'B' is the correct answer.

.

The 'reveal' of the correct answer to the other challenge question has been very consistent in avoiding elucidation of critical or even counter intuitive phenomena. The correct answer is clearly just an indication of which of the provided choices is the best fit without slipping up suggesting possession of understanding, reason in the correct direction, or any clues along those lines to others.It has taken me a while, but not only have I selected the correct answer, but I also got it right by not attempting discussions about the involved phenomena.

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lyn
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#5

Re: ESDU Challenge: Cabin Noise in a Gulfstream III

07/19/2014 9:56 PM

Just issue a Telex Airman 850 Lightweight ANR Headset for each seat.

If you want a real challenge, try to cancel the blade passage cabin noise in a Beech Starship.

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Doorman (1); lyn (1); SolarEagle (2); truth is not a compromise (1)

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