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The present work is devoted to search for the optimum wind farm layout using binary real coded genetic algorithm (BRCGA) based local search (LS); gathering robust single wake model with suitable wake interaction modeling. The binary part of genetic algorithm (GA) is used to represent the location of turbines; while the real part is used to give the power generated by each turbine at its location. In addition, the solution quality is improved by implementing LS technique; where it intends to find the optimal solution near the approximated solution obtained by BRCGA. The Jensen wake model along with the sum of squares model are used to obtain the available power for each turbine; where it is considered one of the most common analytical models used for wind farm optimization. Siting improvement is achieved, as compared with earlier studies. [ABSTRACT FROM AUTHOR]

Simulations of wind turbine wakes are presented in this paper using the three-dimensional Reynolds- Averaged Navier-Stokes (RANS) equations employing the k-ε turbulence model appropriately modified for the atmospheric flows. The actuator disk approach is used to model the action of the turbine rotor. Modified formulations of the inlet conditions and the wall functions are used to allow consistency between the fully developed atmospheric boundary layer (ABL) inlet profiles and the wall function formulation. Results are presented and compared with three wind turbines running under neutral atmospheric conditions. The results demonstrate that the accurate simulation of the atmospheric boundary layer applying enhanced inlet conditions and wall function formulation consistent with the k-ε model can give very useful information about the wakes, directly contributing to the accurate estimation of the power of the downstream turbines. [ABSTRACT FROM AUTHOR]

• Numerical investigation on a hybrid vertical axis wind rotor performance. • The proposed hybrid rotor has twisted modified Savonius blades. • The effects of attachment angle, radius ratio, and number of blades are explored. • The variation of radius ratio has more effect than attachment angle. • The proposed rotor shows high starting ability along with high performance. The present paper introduces a numerical investigation of a proposed hybrid vertical axis wind rotor performance. This proposed hybrid wind rotor has twisted Savonius blades with a modified blade profile combined with 2/3 Darrieus blades. The numerical simulations are aimed to explore the effects of the blade's attachment angle, radius ratio, and number of blades. The utilized Darrieus blades are straight, with an NACA0021 airfoil profile. It is clear from the hybrid rotors results obtained at a low radius ratio of β = 0.27 that, the optimum attachment angle is ϕ = 30°. Furthermore, there is a noticeable enhancement in the starting ability, especially through orientations where the standalone Darrieus rotor has degraded static torque. Different radius ratios, 0.25 to 0.5, are trained at the optimum attachment angle of 30°, for both 2 and 3 bladed hybrid rotors. It is found that the influence of the radius ratio variation on the performance of the tested hybrid rotors is more significant than that of the attachment angle and the optimum radius ratio is found to be β = 0.43. Adjusting both the radius ratio and attachment angle shows the best performance of the proposed hybrid rotor at β = 0.43 and ϕ = 30°, with a peak performance of Cp max = 0.49. [ABSTRACT FROM AUTHOR]

In the present work, the wake behavior of wind turbines, operating under thermally-stratified atmospheric boundary layer (ABL), is numerically investigated. The steady state three dimensional Reynolds-Averaged Navier–Stokes (RANS) equations, combined with the actuator disk approach, are used in the simulation. The standard k-ε turbulence model as well as a modified one namely El Kasmi model are adopted. Two different methods are used and compared, for representing the atmospheric stratification flow conditions: In the first one (direct method), the energy equation is considered along with mass, momentum, and turbulence model equations. In the second one (indirect method), stratification is modeled by means of additional buoyancy production and dissipation terms. Such terms are added to the turbulent kinetic energy and dissipation rate equations, instead of solving the energy equation. The results obtained from both methods show a reasonable agreement with the experimental data available from the literature. Moreover, it is concluded that, there is no significant difference between the predicted results from both methods. Further, the effect of the atmospheric stability class on the wake deficit and the available wind power in the wake region has been also investigated using the indirect method. It has been found that, there is a significant influence of the different atmospheric conditions on the wake behavior. In particular, the wake region becomes smaller with the decreasing of atmospheric stability, and hence a higher wind power in the wake region is observed for unstable conditions. [ABSTRACT FROM AUTHOR]