enhancement effect of multi-stage inducing duct on the wind velocity profile

To extracting power from the wind, the high enough velocity of the wind is the key factor. but, winds with high enough velocities are not available in most areas, and therefore, finding a method to enhance the velocity potential of the low-speed winds has been a serious challenge in wind engineering. in this research study, a hollow duct with a specific configuration, we called multi-stage inducing duct, is presented which is capable to cause a great enhancement in the velocity profile of the low-speed winds, enough to start most of the small horizontal wind turbines. for example, a three-stage inducing duct can increase the wind velocity from 3 m/s to 9.3 m/s on average at the first stage throat of the duct, which equals an increase of 29-times in wind potential power! this configuration of the duct has been introduced, numerically simulated and the effect of its various geometrical parameters investigated. the effects of wind velocity and the number of the stages on the duct performance are investigated, and finally, a study on the relative effectiveness of adding each of the stages is carried out to help us decide where the upper limit for the number of the stages is.