"...3-blade rotor it might, but in a 'theoretical' 4-blade rotor..."
Dave, i think you need to find a good aerodynamic efficiency justification for 4 blades per rotor. Removing vortex wake interaction between both rotors will by itself greatly reduce vibration. [Slightly off topic]
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Nick,
"Most of the time, we try to tune the blade to be compliant (softer) in a given frequency where it can help relieve these vibrations or absorb them."
Has any work been done on blade material damping? I also imagine that the gearbox mounting is carefully designed to maximise lateral compliance (good isolation in X and Y), while minimising torsional compliance (good manouvreing). Are hydromounts the norm (hydraulically damped elastomers - usually Lord or Simrit), and have active mounts been considered?
"The response of the fuselage is important to vibration supression."
I've done a lot of work on modal response and input point force spectrum sensitivity. Powertrain mounting systems are normally the best means of isolation, although you can tune structures to some extent. Since i'm understanding that Np ties up with one of the main airframe bending modes, i imagine structural tuning to be limited.
Mart
[Edit: typing while watching Disco do it's dance with the ISS]
Last edited by Graviman; 28th Jul 2005 at 17:24.