Page 289 - Handbook of Energy Engineering Calculations

There are two types of forces operating on the blades of a propeller-type wind
turbine. They are the circumferential forces in the direction of wheel rotation
that provide the torque and the axial forces in the direction of the wind

stream that provide an axial thrust that must be counteracted by proper
mechanical design.
The circumferential force, or torque, T is obtained from

where

T = torque, N or lb f
ω = angular velocity of turbine wheel, m/s or ft/s
D = diameter of turbine wheel = , m or ft

N = wheel revolutions per unit time, s −1
For a turbine operating at power P, the torque is given by

For a turbine operating at maximum efficiency η max = 16/27, the torque is

given by T max

The axial force, or axial thrust, is