DEM computational modeling of flow over wind-turbine sections under varying wind speed and direction conditions

A summary of the core computational algorithm of the Discrete Element Model (DEM) FLOWER code, which was developed by implementing Newton's original "discrete" Moving-Material-Domain (MMD) concepts, as the EDAN (Euler Domain Assimilated Newtonian) formalism, was presented. New generation DEM code AERO-FLOWER was used for the simulation of fast-transient air-flow conditions over three selected blade-sections (NACA 4424, NACA 4421, DU 00-W2-401) of an AEOLUS II wind-turbine blade. For each blade-section, simulations were started from parked-blade (stationary) conditions, with the oncoming wind velocity considered as 10m/s or 20m/s, along the rotor-axis (zero yaw). The tangential-velocity conditions were started as 0m/s, and were increased, intermittently, as 10m/s, 20m/s, and 40m/s, until the Torque Termination Limit (TTL). The results for tangential-force and normal-force coefficients clearly indicated the continuous presence of gradually weakening, but persistent, fast-transient characteristics of the dynamic-stall regimes, which verified the critical need for Shedding-Eddies Simulation (SES) capabilities.