Wind tunnel testing of a wind turbine in complex terrain

Abstract

The paper describes the development of a scaled model of complex terrain, suitable for terrain-wind turbine interaction wind tunnel studies, taking into account flow similarity criteria. The size and the geometry of the experimental model of the complex terrain were refined using results of CFD simulations in order to achieve the best possible flow similarity and avoid edge effects arising from the finite (relative to the rotor size) terrain geometry. Moreover, Particle Image Velocimetry was used to survey the flow field on a longitudinal plane along the terrain center line. Flow measurements with and without a wind turbine model enabled to quantitatively evaluate the speed up produced by the terrain in the region of the wind turbine and the effect of the terrain on the wake characteristics of the wind turbine model.

The Ability of Convergent–Divergent Diffusers for Wind Turbines to Exploit Yawed Flows on Moderate-to-High-Slope Hills

“…For instance, among the first, there are the experimental wind tunnel investigations [18][19][20]: study [18] is an analysis of the flow characteristics and speed-up on low and smoothed hills of different shapes and aspect ratios (i.e., half-length to the height of the relief); study [19] is focused on the flow separation behavior occurring in two-dimensional hills with trapezoidal profiles, characterized by different slopes; in [20], the flow acceleration characteristics and the turbulence generation over sharp-edged escarpments with different slopes are assessed. The investigations with turbines in the atmospheric boundary layer can be performed with a scaled model in a wind tunnel [21] or by means of full-scale CFD, of which the most accurate are based on the Large Eddy Simulation method [22][23][24] or on the Delayed Detached Eddy Simulation [25]; in some cases, a simplified two-dimensional shape of hills is assumed [22,23], and otherwise, the complex topography of a real terrain is reproduced [21,[24][25][26]. Considering the actual topography can be important because it influences wind intensity and direction and the intensity of turbulence, in [26], it is proved how even relatively very low reliefs, located upstream of the escarpment on which the turbines are positioned, can significantly influence the characteristics of the wind reaching the rotors.…”

Effect of Topography Truncation on Experimental Simulation of Flow over Complex Terrain

“…An in-depth understanding of complex turbulent flows is essential for greatly improving simulation accuracy, especially for numerical simulations including the large eddy simulation (LES) and the unsteady Reynolds-averaged Navier-Stokes (URANS). Significant effort has been devoted in recent years to gaining a better understanding of flow characteristics in complex terrains with wind tunnel testing [2][3][4][5][6]. Furthermore, numerical simulation can be compared to validate results [7].…”