To zeeoo
I basically put al the equations into Matlab (a powerful math solving and simulation package, now common in R&D)
The model adresses
- full dynamics: I checked this with the books of Eric Dick, Gordon Leisman and Wayne Johnson. The equations are similar, but adapted to the specifics of the R44 rotor head. It is not just a linear or first harmonic kind of thing, but the full math.
- airfoils : I assumed a 63015 of which I recalibrated the lift and drag coefficients using XFoil from MIT (freeware). This allows to refine the simple C times v square kind of stuff. Especially in the 0,6 to 0,8 Mach range
- tip losses
- reverse flow
Simplifications
- uniform inflow (I just solve - be it the full- Glauert equation to determine the induced velocity). This is not OK for 0-20 knots transition and during flow reversals such as before entering autorot, but it can be compensated (tdb)
- stiff blades . This I will refine, both bending and twisting, but for that I need to measure the blades otherwise I get GIGO (garbage in and out). I am still puzzled with the famous german film of the rotating blades, so I want to model this and simulate it.
When validating the results I had several 'sleepness nigths' not believing what I saw. After some validation work I am now convinced and 'understand' it better, although some of the stuff is at first very weard (for me at least I am not a Helo-professional).
For those who care about this egg-head stuff an example : total lift per blade plotted as a function of rotation angle, in the following case : R44 level flight (100 knots), fuel fuel, 1 POB, required cyclic and heli pitching.
I show a 'camera type picture as viewed from the front to the rear'. Looking at this I first thought : this can not be It will tip the whole machine, but actually it doesn't....
Delta3