The Yawing Behavior of Horizontal-Axis Wind Turbines: A Numerical and Experimental Analysis

Abstract

The yawing of horizontal-axis wind turbines (HAWT) is a major topic in the comprehension of the dynamical behavior of these kinds of devices. It is important for the study of mechanical loads to which wind turbines are subjected and it is important for the optimization of wind farms because the yaw active control can steer the wakes between nearby wind turbines. On these grounds, this work is devoted to the numerical and experimental analysis of the yawing behavior of a HAWT. The experimental tests have been performed at the wind tunnel of the University of Perugia on a three-bladed small HAWT prototype, having two meters of rotor diameter. Two numerical set ups have been selected: a proprietary code based on the Blade Element Momentum theory (BEM) and the aeroelastic simulation software FAST, developed at the National Renewable Energy Laboratory (NREL) in Golden, CO, USA. The behavior of the test wind turbine up to ±45 • of yaw offset is studied. The performances (power coefficient C P ) and the mechanical behavior (thrust coefficient C T ) are studied and the predictions of the numerical models are compared against the wind tunnel measurements. The results for C T inspire a subsequent study: its behavior as a function of the azimuth angle is studied and the periodic component equal to the blade passing frequency 3P is observed. The fluctuation intensity decreases with the yaw angle because the distance between tower and blade increases. Consequently, the tower interference is studied through the comparison of measurements and simulations as regards the fore-aft vibration spectrum and the force on top of the tower.

Investigations on the Unsteady Aerodynamic Characteristics of a Horizontal-Axis Wind Turbine during Dynamic Yaw Processes

“…The blade passing frequency of the NREL 5-MW turbine is about 0.2017 Hz (1P fluctuation), and is clearly the main frequency of the two yawing processes. Both are 0.6 Hz (which is approximately a 3P rotor fluctuation), which is similar to results presented by Castellani [20]. Figure 16a shows a secondary frequency of 0.2 Hz (1P fluctuation).…”

“…The AOA distribution presented in Figure 9 takes into account the advancing and retreating effects, as previously shown by Castellani [20] in the yawed simulation of a HAWT using the BEM model. Comparing the simulation results for CFD and FAST, the same trends can be observed along the blade span, whereas the AOA value is much larger than the FAST result.…”

“…For the axial flow, some large abnormal fluctuations in the AOA and aerodynamic loads can be observe d. Differences in the results of the CFD and FAST methods mainly occur along the inner board, owing to flow separation, which lead to smaller aerodynamic loads compared to those computed by the BEM model that does not consider flow separation. The AOA distribution presented in Figure 9 takes into account the advancing and retreating effects, as previously shown by Castellani [20] in the yawed simulation of a HAWT using the BEM model. Comparing the simulation results for CFD and FAST, the same trends can be observed along the blade span, whereas the AOA value is much larger than the FAST result.…”

Perancangan Sistem Kontrol Otomatis Turbin Angin Yaw Direction

“…Blyth membangun turbin angin setinggi 10 meter untuk menjadi sumber listrik penerangan pada pondok miliknya [8]. Penemuan signifikan selanjutnya adalah ditemukannya kedua jenis turbin angin yang digunakan hingga saat ini yaitu vertical axis wind turbine (VAWT), dan horizontal axis wind turbine (HAWT) [9]. VAWT Pada artikel ini tipe turbin angin yang di analisa adalah turbin angin HAWT.…”

Experimental Vibration Analysis of a Small Scale Vertical Wind Energy System for Residential Use

“…The absence of yaw controls [11] is advantageous for small size applications, because diminshing the use of actuators and controllers also means reducing the initial required investment.…”