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Old 03-11-2021, 09:09 PM   #2 (permalink)
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Join Date: Aug 2010


The core results are accurate enough for most people. There are problems with the kinetic energy calc just because of how you simplified mass distribution for example, but it is going to be within 20% or so for most configs, which is again, good enough for inquiring minds.

There seems to be some weirdness where if say you enter 16in for Rcg, and run the Compute F function, and then you change Rcg to something like 14”, it will just ignore that and revert to 16in. Probably better to throw an error for non-accepted units/notation.

Some units are incorrect. F is a force, so the resultant would be 100lbf, not 100lb.

Just a few suggestions if you want to extend the app without a bunch of effort. Several things are easy to calculate and are useful:
1. Ask for blade chord, and then output Reynolds Number for the blade perhaps over 5-10 stations along the radius.
2. For FF, allow input of airspeed, and then show local peak and min airspeed on the blade for advancing and retreating by station, with Reynolds number (extension of #1).
3. Include machine mass and blade count along with blade chord, to output disc and blade loading
4. Extending #3, output average flow velocity and mass flow at standard temp/pressure.
5. Extending #4, determine power required (a way to approximate rotor efficiency- not a great one since you are assuming all kinds of things in #4, but still- helps people to understand why rotor area has such a large impact on power absorbed.

It might also be fun to sort of put a simple reference chart for kinetic energy of a thrown blade at the hub, where for example you could post just say things people understand from the normal world- baseball at 90mph, AK47 round at the muzzle, etc just to let people better understand what sort of energy is in play with RPM and blade mass etc. Most people have no idea what 1000J means- even if they know the technical definition.
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