Generation of fluid force oscillation due to wind direction in a longitudinal vortex driven horizontal axis circular cylinder blade wind turbine

Abstract

A prediction model of the fluid force on a cylindrical blade driven by the Necklace vortex is developed and verified by experiments when the yaw angle is given. Based on the measurement results of the velocity ratio of blade and wind velocity and the fluid force coefficient at zero yaw angle, a prediction model for the relationship between the rotation angle of the cylindrical blade and the fluid force coefficient considering the yaw angle was derived from the analysis of the two-dimensional velocity components acting on the cylindrical blade. The validity of the predictive model was demonstrated by experimental verification. From the comparison, it was found that there was a time delay in the formation and disappearance of the Necklace vortex. Based on the experimental results, the characteristics of the fluid force acting on the cylindrical blade were classified into five angular regions and based on the characteristics of the effective velocity ratio considering the yaw angle, the classification was made into 12 angular regions. Depending on the yaw angle, wind speed, and rotational speed of the blade, all of these regions may appear or only some of them may appear. Therefore, the yaw angle characteristics of the cylindrical blade wind turbine driven by the Necklace vortex are very complicated.