Experimental and numerical study of the novel diffuser with a passive adaptive flexible flange for improving the shroud augmented wind turbine

This study proposed a new type of diffuser which can not only accelerate the wind approaching the turbine before wind velocity reaches the rated velocity, but also reduces the wind drag on the diffuser when wind velocity is overrated one. A passive adaptive flexible flange constructed of two flexible cantilevered plates is developed for the diffuser. The flow distribution around the diffuser equipped with a flexible flange, as well as the wind drag on the diffuser, varies with the deformation of the flexible flange under the wind drag. Wind tunnel experiments and numerical analysis are conducted to study the flow distribution around the diffuser and the corresponding wind drag on it at different wind velocities. Experimental results reveal that the drag reduction rate of the diffuser with the passive adaptive flexible flange is 17.9% at the velocity of 20 m/s. Numerical results overall match well with the experimental measurement, such as velocity and pressure distributions, although the simulated values are slightly lower than the experimental ones.