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Bladeless wind turbine (BWT) is a flexible cylindrical structure that extracts energy from wind by utilising vortex-induced vibration (VIV) - aerodynamic forces and the resulting structural vibration. This work focuses on taking possible advantage of the increase in lift forces in the similar fashion to birds flying in a V-formation. The purposes of the present study are 1) to study the flow pattern and characteristic around two BWTs which are cylindrical structures in the same flow field and 2) to study the extra lift force generation of the system. 2–D CFD models are used to simulate flow of stationary cylinder of BWTs at Re = 105. The two different turbulent models, Reynolds Averaged Navier-Stokes shear-stress transport k(RANS–SST k) and Detached Eddy Simulation shear-stress transport k(DES–SST k) are investigated. The results show that only DES–SST kgives converged results, therefore, DES–SST kis selected for the additional studies of two cylindrical structures. From 2–D CFD simulation, the one BWT in flow field case produces lift coefficient 0.851. In the case of two BTWs in same flow field (BWT no.2 is located at x = 3D, y = 0D, directly downstream of two cylinders), BTW no.1 and BWT no.2 show greater lift coefficients of 0.893 and 1.841, respectively. This result indicates that the kinetic energy generation of the downstream BWT in the two BWTs system in this study is greater than the baseline BWT with an increase of 116% of lift. Further work is needed to determine the optimum location of the behind wind turbine for greater lift and result to increasing of energy produce of the system.

Figure 1. Static (dashed line) and dynamic (solid line) aerodynamic forces and moments of an aerofoil in pure pitching oscillation.The numbers refer to key dynamic stall events described in the text.