
#55
Jan2110, 09:24 PM

PF Gold
P: 3,021





#56
Jan2110, 09:36 PM

P: 4,780




#57
Jan2110, 09:44 PM

PF Gold
P: 3,021





#58
Jan2110, 09:45 PM

Sci Advisor
P: 5,095

You asked for it. I scanned this in from one of my references. The mB notation refers to the mth harmonic/mode and B is the number of blades. The rest should be somewhat decipherable.




#61
Jan2110, 09:48 PM

PF Gold
P: 3,021





#62
Jan2110, 09:51 PM

Sci Advisor
P: 5,095

BTW...This all stems from the basic wave equation. I sat through many a proofs showing this stuff and it is amazing to see just how much can be pulled from such a seemingly unimposing equation. You may want to look up Ffowcs Williams for a reference.




#63
Jan2110, 10:31 PM

P: 4,780

Bessel function, wave equations??? Eeeeuccccwkkkk!
Quick, something more pleasing to the ear: Laplace transforms, Bode Diagrams, Nyquist plots, PSD, Autocorrelations.......ahhhhhhhhhhh. I can breathe again, whew. 



#64
Jan2210, 12:09 AM

P: 4,780

I'll tell you what, if you guys want to formulate a list of questions, I can email them to Dr. Moore and report back his answer. I'd prefer to keep the list short, so think of good ones.




#66
Jan2210, 01:03 PM

PF Gold
P: 3,021





#67
Jan2210, 01:13 PM

Sci Advisor
P: 5,095

All of the ones I have used and seen have no external means for cooling other than some form of exposure to the outside air.




#68
Jan2210, 01:29 PM

PF Gold
P: 3,021





#69
Jan2210, 01:47 PM

PF Gold
P: 3,021





#70
Jan2210, 02:08 PM

Sci Advisor
P: 5,095

That is not a proper statement. It should read that the ENGINE noise is lower, not the overall aircraft noise. You can not change the acoustic performance of a prop by changing the thing that drives it. The prop noise will still be there.




#71
Jan2210, 02:24 PM

PF Gold
P: 3,021

Assumptions per prop: B (blades) = 4 y = sideline distance = 450 ft D = 6 ft T = thrust = 300 lbs takeoff W = shaft power = 30 HP c0 = 1000 ft/s zeff = 0.8 I want worse case, so I'm bypassing all the modal analysis and setting the sincx and Bessel functions to one. Edit:Still need help on defining theta? It can't be zero or the SPL is zero. 


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