Wind tunnel study on wind and turbulence intensity profiles in wind turbine wake

Abstract

In recent years, there has been a rapid development of the wind farms in Japan. It becomes very important to investigate the wind turbine arrangement in wind farm, in order that the wake of one wind turbine does not to interfere with the flow in other wind turbines. In such a case, in order to achieve the highest possible efficiency from the wind, and to install as many as possible wind turbines within a limited area, it becomes a necessity to study the mutual interference of the wake developed by wind turbines. However, there is no report related to the effect of the turbulence intensity of the external flow on the wake behind a wind turbine generated in the wind tunnel. In this paper, the measurement results of the averaged wind profile and turbulence intensity profile in the wake in the wind tunnel are shown when the turbulence intensity of the external wind was changed. The wind tunnel experiment is performed with 500mm-diameter two-bladed horizontal axis wind turbine and the wind velocity in wake is measured by an I-type hot wire probe. As a result, it is clarified that high turbulence intensities enable to the entrainment of the main flow and the wake and to recover quickly the velocity in the wake.

An investigation of in‐field blockage effects in closely spaced lateral wind farm configurations

“…The sensor that was available to meet this objective was a single‐normal hot‐wire probe connected to a constant temperature hot‐wire anemometer. Single‐normal hot‐wire probes have been used by several authors to characterize the flow downstream of scaled wind turbines . The hot‐wire probe was manufactured by Auspex Scientific (Lehigh Valley, Pennsylvania) and had a 5 μm tungsten welded sensor with a length of 1 mm.…”

Atmospheric Turbulence Effects on Wind-Turbine Wakes: An LES Study

“…Evidence also shows that the turbulence level in the incoming flow affects the rate at which this velocity deficit decreases with downwind distance from the turbine (i.e., the wake recovery rate). In particular, both simulations [9][10][11] and experimental studies [6,[12][13][14] have shown that stand-alone turbine wakes recover faster in conditions of higher turbulence intensity levels in the incoming flows. This effect is found to affect the performance (power output) of the downwind turbines in large wind farms.…”

Effect of turbulent inflows on airfoil performance for a Horizontal Axis Wind Turbine at low Reynolds numbers (part I: Static pressure measurement)

“…The turbulence intensity in the longitudinal direction TI and Reynolds numbers Re were defined as follows [13,14,16,23,31,35,41,42]:…”

“…Friction force acting on the blade surface was ignored. By using pressure measurement results, the lift and drag coefficients were computed according to the following equations [7,15,16,31,45]: …”

“…As a result, the simple design requirements and standards for wind turbines as defined by the IEC 61,400 [13e15] included specifications for extreme wind loading conditions. However, it was still very different to develop a HAWT with high efficiency in turbulence environment, especially at low Reynolds numbers [16].…”