Interesting. If I do build an helo with 2 Blades and an helo with 5 Blades of the same shape as the 2 bladed one, that changes nothing.
OK, my bad. I was fixated on the 2 bladed head. There is BTW, an interesting piece in the Prouty, how to design a helicopter and how to decide on the number of blades.
Not for a man that only refers to the environment 3 times during layout. And thought (honestly) first about an magneto-fluid like behaviour.
Would you care to explain? I don't get it. Both.
The problem occurs simply in scale....
Why? VRS occurs in every size of rotor. The drone web-community is full of tips and tricks for avoiding VRS and so are the RC sites.
The thing is only the point and time you are referring to. The downwash referred to the environment is higher on the heavier helo after an infinitessimal short time period after inducing the same controls on both helos.
Ok, real world behavior. In the infinitessimal short period of time after a control input absolutely nothing happens. Rotors suffer from a phase lag, because the blade is not stiff. OK, that was unfair. The point I want to make here is, that helicopter design involves to the day still trial and error. Why computed fluid dynamics get better and better, airplane aerodynamics are easy compared to a helicopter. Have you ever watched that
video of a rotor blade in flight? Worth a look. At every instant the blade flexes and therefore AoA and lift change at every point along the blade. And it's going round. And its going forward. And the fuselage does have some influence. And behind the rotorhead everything changes again. Everything you calculate will still be further from the real world than on an plane.
The VRS is, while quite good understood (but not completely), not a very important subject in helicopter aerodynamics. I believe there wasn't any fundamental research on this for decades. Despite some self-proclaimed pilot gods opinion, it does not kill that many people. CFIT is way more important, but that has nothing to with aerodynamics.
If you are interested:
Shawn Coyle: Little Book of Autorotations
Shawn Coyle: Cyclic & Collective
These are as close to the bible for pilots as it gets.