Contribution to improved eddy-viscosity modeling of the wind turbine - to - wake interactions

In the present study, we focus on testing, validation and comparative assessment of different modeling strategies for numerical simulations of the wind turbine wake interactions under neutrally stratified atmospheric conditions. The final goal of our investigation is to propose a numerically robust and a relatively simple, but sufficiently accurate turbulence model, which will be able to predict the correct behavior of wind turbine wake interactions in complex terrains or within urban areas. In this work, we adopted the actuator disk model (ADM) to represent wind turbine blades effects. The non-rotational and rotational actuator disk models are implemented in our in-house code, which was previously extensively tested and validated against a series of environmental studies in both laboratory and full-scale applications (including effects of complex orography/terrain, thermal stratification, vegetation, arrays of urban buildings). We reviewed sets of existing RANS two-equation based models with specific extensions for the wind turbine wake regions and selected two of the currently most-used models for simulations of wind turbines. To strengthen the physics of the flow foundation of modified RANS-type k−ɛ models for wind turbine effects, we propose an improved model based on Durbin's time-limiter concept. A comparative assessment of turbulence models is performed on a series of test cases that include the real- and laboratory-scale single and multiple horizontal axis wind turbines for which detailed experimental measurements are available. The proposed variant of the model provided results in good agreement with measurements, without any additional adjustments of the empirical input, and outperformed the currently mostly used models in wind engineering. The proposed model is recommended for future use in optimization studies of the wind-turbine placement in the complex urban areas, and eventually, for improving layouts of wind farms.