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Post by Br. Marius on Mar 5, 2015 18:30:07 GMT
An articulated rotor with 6% flap hinge offset is rotated first in vacuum and then in air. Discuss the nature of eigenvalues in rotating as well as fixed coordinate systems for both conditions (Assume Nb = 4 and γ = 8). Identify progressive and regressive waves if any.
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Post by Deleted on Mar 9, 2015 13:00:23 GMT
Problem 3. No regressive mode in air and regressive in vacuum Attachments:ENAE633PR3.pdf (573.97 KB)
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Post by Br. Marius on Mar 10, 2015 17:09:45 GMT
So, I am using n = 1 because that's what Chopra said...but I can't find where he defined n in my notes. What is n in this context?
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Post by Br. Marius on Mar 10, 2015 17:33:21 GMT
Also, I think the answer is more nuanced, Mario. Looking at a rotor, I can remember seeing it spin in different directions depending on how fast it is rotating. This makes me think that different natural frequencies are being excited as the rotor spins up or down, so we could see either regressive or progressive waves depending on the excitation. Otherwise, I think that our solutions are the same. Attachments:HW6P3.pdf (189.72 KB)
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Post by Deleted on Mar 10, 2015 19:15:02 GMT
I just saw this and I am not sure if you found your answer for n but in his pdf emailed notes he defines it as a harmonic index dependent on the number of blades and if they are even or odd (page 120). Sorry I thought this was problem 2 not 3. Sorry for the confusion.
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Post by Br. Marius on Mar 11, 2015 19:19:03 GMT
Alright, I think I got it all straightened out...except that in the posted solutions only one set of waves (progressive or regressive) is mentioned. Why is it just one or the other based on a single set of frequencies out of the larger set obtained for the given rotor and condition?
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