NUMERICAL ANALYSES OF A STRAIGHT BLADED VERTICAL AXIS DARRIEUS WIND TURBINE: VERIFICATION OF DMS ALGORITHM AND QBLADE CODE

Abstract

Wind energy is among the most cost-effective renewable energies. Till date,turbines with different configurations had been designed to harness windpower, each having unique superiorities. Darrieus turbines are one of themostly investigated vertical axis wind turbines using either experimental ornumerical methods. Experimental analyses are time consuming works whichrequires high amount of effort and expenses. Thus, computational fluiddynamics (CFD) methods have been commonly used by scientists andengineers in order of obtaining detailed performance and illustration of thefluid flow. Contrary to the horizontal axis machines, Darrieus turbines aredifficult to be analyzed by CFD algorithms due to high pressure and velocityvariations which arise from extreme changes in the angle of attack beyondthe stall condition at different azimuthal position of the blades. Therefore,more simplified numerical models are generated employing double multiplestreamtube (DMS) theory together with additional improvements. QBlade isone of the mostly used numerical methods based on the lifting line freevortex wake method developed for calculating rotor aerodynamics. The mainscope of this study is to design a straight bladed Darrieus turbine (D=1028mm, H=1460 mm, N=3) and to verify the double multiple streamtube theoryand QBlade algorithm with the experimental and computational works.Analysis results represented good agreement with the previous studiesespecially at lower TSR ranges. Compare to the experimental results, anoverestimation in the power coefficient is obtained at low free stream speedand high TSR ranges after exceeding the peak point. Sensitivity of the modelto the Re number variations have also been outlined.