- #1
anders
- 9
- 0
Hello!
We all know that helicopters can hover, stand still in the air. As they do this, a powerful downwash, down-directed wind, results. This is very obvious when the helicopter is near the ground, since the downwash often kicks up a dust cloud.
My question is this: How strong will this downwash be?
I'm looking for an approximate formula, a function of the following parameters:
* Lift (vertical force needed to keep helicopter hovering)
* Density and Viscosity of the air
* Rotor diameter (diameter of the helicopters 'propellor')
(Have I missed any important parameter?)
My guess is that the downwash will:
- Increase with higher lift
- Increase if viscosity decreases.
- Increase with smaller rotor-diameters
best regards,
/anders
We all know that helicopters can hover, stand still in the air. As they do this, a powerful downwash, down-directed wind, results. This is very obvious when the helicopter is near the ground, since the downwash often kicks up a dust cloud.
My question is this: How strong will this downwash be?
I'm looking for an approximate formula, a function of the following parameters:
* Lift (vertical force needed to keep helicopter hovering)
* Density and Viscosity of the air
* Rotor diameter (diameter of the helicopters 'propellor')
(Have I missed any important parameter?)
My guess is that the downwash will:
- Increase with higher lift
- Increase if viscosity decreases.
- Increase with smaller rotor-diameters
best regards,
/anders