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The use of wind energy, the area of wind farms, and the length of wind turbine blades continuously increase with the increase in energy demand. This study aims to simulate large wind farms in the atmospheric boundary layer with different double-rotor (DR) wind turbine arrangements using large eddy simulation. The effect of four DR wind turbine arrangements on the efficiency of a large wind farm was investigated in this study. All simulations were performed using the OpenFOAM solver. The performance of different turbine arrangements was investigated based on the mean velocity, the extent of the wake region, mean kinetic energy, and turbine power. Results showed that the arrangement of DR turbines with transverse spacing produces higher power than other layouts. Moreover, DR layouts produce the same power as single-rotor layouts with a short blade length. This scenario is important from an economic point of view. [ABSTRACT FROM AUTHOR]

The influence of the velocity ratio (VR) between the jet and main flow on the wake structure and aerodynamic loss of the trailing edge jet is studied using particle image velocimetry and numerical simulations. Three different velocity ratios, namely, VR = 0.5, 1.0, 1.5, are chosen for this comparative study. The Reynolds number (Reh) based on the slot height (h) and the mainstream velocity (U0) are 3380. Results show that the influence of jet on wake structure is significant such that the wake region shrinks and the turbulent kinetic energy is enhanced as the velocity ratio increases. The distribution area of strong vorticity is enlarged with increasing velocity ratio. By using proper orthogonal decomposition and fast Fourier transfer analysis, the variation of velocity ratio demonstrates significant impact on vortex shedding and turbulent kinetic energy. The aerodynamic loss coefficient is nearly constant between VR = 0.5 and 1.0, but increases by 3.25 % as the velocity ratio increases from 1.0 to 1.5. [ABSTRACT FROM AUTHOR]