标题：Effects of time-varying freestream velocity on energy harvesting using an oscillating foil
作者：Ma, Penglei; Wang, Yong; Xie, Yudong; Huo, Zhipu
作者机构：[Ma, Penglei; Wang, Yong; Xie, Yudong; Huo, Zhipu] Shandong Univ, Sch Mech Engn, Key Lab High Efficiency & Clean Mech Manufacture, Jinan 250061, Shand 更多
通讯作者地址：[Wang, Y; Xie, YD]Shandong Univ, Sch Mech Engn, Key Lab High Efficiency & Clean Mech Manufacture, Jinan 250061, Shandong, Peoples R China.
关键词：Tidal energy; Oscillating foil; Time-varying freestream; Energy; harvesting; Hydrodynamic
摘要：The hydrokinetic turbine, using an oscillating foil to extract tidal energy, offers an obvious advantage in shallow water. The software Fluent is used to solve the 2D unsteady incompressible Navier-Stokes equations around an oscillating foil with computations performed with using NACA0015 foil. The parameter mu(x) which indicates the oscillation frequency ratio between the freestream and foil motion, is introduced to identify the effects of time varying freestream velocity. The mean power coefficients are examined over one period and eight periods, the force evolution is reviewed, and the flow fields around foil are analyzed. The results indicate that time-varying freestream velocity leads to fluctuation of the cycle-averaged power coefficient (C-P) over bar, with the maximum fluctuation of (C-P) over bar exceeding 16%. A similar variation trend is observed for (C-P ) over bar versus mu(x) under different motion parameters. Furthermore, it is found that C-Pmean the mean power coefficient over eight periods, fluctuates slightly with mu(x), and the maximum fluctuation of C-Pmean is less than 4%. Therefore, the time-varying freestream velocity slightly affects the total energy harvesting efficiency for a lengthy period.