Apparent wind in knots and degrees. Note that a number of additional factors come into play when converting the measurements from the masthead anemometer into the true wind if a high degree of accuracy is required, including the following: In the presence of a current, the true wind is considered to be that measured on the craft drifting with the water over the bottom, and wind with respect to the sea bed as the "ground" or "geographical wind". The apparent wind on board (a boat) is often quoted as a speed measured by a masthead transducer containing an anemometer and wind vane
Variable speed wind turbine length of the blade, formula_4 is the velocity of the wind, and formula_5 is the power coefficient for the wind turbine. The power coefficient is a representation of how much of the available power in the wind is captured by the wind turbine. The torque, formula_15, on the blades is given by the ratio of the power extracted to the rotor speed, formula_2: formula_17 The rotor speed can be related to the wind speed, formula_4, through the tip-speed ratio, formula_6: formula_1 Thus we can get the following expressions for torque and power: formula_21 and formula_22 From the above equation, we