Momentum theory
by gowtham[ Edit ] 2010-02-16 19:00:40
In fluid dynamics, the momentum theory or Disk actuator theory is a theory describing a mathematical model of an ideal actuator disk, such as a propeller or helicopter rotor, by W.J.M. Rankine (1865), Alfred George Greenhill (188
and R.E. Froude (1889).
The rotor is modeled as an infinitely thin disc, inducing a constant velocity along the axis of rotation. The basic state of an helicopter is hovering. This disc creates a flow around the rotor. Under certain mathematical premises of the fluid, there can be extracted a mathematical connection between power, radius of the rotor, torque and induced velocity. Friction is not included.
The power required to produce a given thrust is:
P = \sqrt{\frac{T^3}{2 \rho A}}
Where:
* T is the thrust
* ρ is the density of air (or other medium)
* A is the area of the rotor disc
