Once in operation, a wind turbine experiences a wide range of conditions. Wind turbines come in a variety of sizes.

( September 2011) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed. Please help improve this section by adding citations to reliable sources. Thus, the maximum power limits of these machines are much higher than those of drag-based machines. Here, the relative wind does not decrease rather, it increases with rotor speed. Lift-based wind turbines typically have lifting surfaces moving perpendicular to the flow. The relative wind aspect dramatically limits the maximum power that can be extracted by a drag-based wind turbine. In the drag force case, the relative wind speed decreases subsequently, and so does the drag force. To extract power, the turbine part must move in the direction of the net force. An example of relative wind is the wind one would feel cycling on a calm day. Typically, the wind turbine parts are moving, altering the flow around the part. The direction of the drag force is parallel to the relative wind. The most familiar type of aerodynamic force is drag. The magnitude and distribution of this force is the primary focus of wind-turbine aerodynamics. The force F is generated by the wind's interaction with the blade. Where P is the power, F is the force vector, and v is the velocity of the moving wind turbine part. Despite its low efficiency, it remains in use because of its robustness and simplicity to build and maintain. The Savonius wind turbine is the most common drag type turbine. Despite being a popular lift-based alternative in the latter part of the 20th century, the Darrieus wind turbine is rarely used today. Accordingly, it is a popular choice for commercial applications and much research has been applied to this turbine. It is a lift-based wind turbine with very good performance. The most common topology is the horizontal-axis wind turbine. The difference between these groups is the aerodynamic force that is used to extract the energy. In general, all turbines may be classified as either lift-based or drag-based, the former being more efficient. The method used to extract power has a strong influence on this. Every topology has a maximum power for a given flow, and some topologies are better than others. Though the details of the aerodynamics depend very much on the topology, some fundamental concepts apply to all turbines. Like most machines, wind turbines come in many different types, all of them based on different energy extraction concepts. Hence, the aerodynamics is a very important aspect of wind turbines. The primary application of wind turbines is to generate energy using the wind. Wind-turbine blades awaiting installation in laydown yard.

Aerodynamic aspect ratio calculator