An Experimental Investigation on the Wake Characteristics and Aeromechanics of Dual-Rotor Wind Turbines

Abstract

An experimental study was carried out to investigate the aeromechanics and wake characteristics of dual-rotor wind turbines (DRWTs ) in either co-rotating or counter-rotating configuration, in comparison to those of a conventional single-rotor wind turbine (SRWT). The experiments were performed in a large-scale Aerodynamic/Atmospheric Boundary Layer (AABL) wind tunnel available at Iowa State University with the oncoming Atmospheric Boundary Layer (ABL) airflows under neutral stability conditions. In addition to measuring the power output performance of DRWT and SRWT models, static and dynamic wind loads acting on those turbine models were also investigated. Furthermore, a high resolution digital particle image velocimetry (PIV) system was used to quantify the flow characteristics in the near wakes of the DRWT and SRWT models. The detailed wake flow measurements were correlated with the power outputs and wind load measurement results of the wind turbine models to elucidate the underlying physics to explore/optimize design of wind turbines for higher power yield and better durability.

Numerical analysis on the performance of Dual Rotor wind turbine

“…Moreover, it compares these performances with the SRWT revealing certain conclusions to be taken into consideration. At low TSR, the front and rear performance are nearly equal and that agrees with previous study (Ozbay, Tian, & Hu, 2015). At high TSR, the effect of the front rotor become dominant and the rear rotor effect is minimized until a TSR of 8 where the Cp of rear rotor is nearly ineffective.…”

An experimental investigation on the wake interferences among wind turbines sited in aligned and staggered wind farms

“…The diameter of the turbine rotors is 280 mm, and the hub height to the wind turbines is 225 mm. Further information about the scaled turbine models is available in Tian et al and Ozbay et al Because the ratio of the swept area of the turbine rotor to the cross‐sectional area of the ABL tunnel is 1:110, the blockage effects of the turbine models on the wind tunnel experimental results can be neglected.…”

A Numerical Investigation of Dual-Rotor Horizontal Axis Wind Turbines Using an In-House Vortex Filament Code (DR_HAWT)

“…The first set of computations was performed at a constant CTSR of 7.5 to avoid simulating the downwind rotor outside its design operating range. loss from the downwind rotor) found in the literature [5,6,16]. It is believed that this lower deficit is due to the lack of tower effect in this study.…”

“…In more recent years, a growing interest in dual-rotor systems which have been extensively employed in the 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 aerospace (e.g., the Soviet Ka-32 helicopter) and marine (e.g., the Mark 46 torpedo with contra rotating propellers) applications-to increase the aerodynamic efficiency of the systems while eliminating the asymmetrical torque experienced by conventional single-rotors-have resurfaced. Although the idea of increasing the amount of rotors per tower is not well accepted within the wind industry, university researchers from the University of Ottawa [5] and the Iowa State University (ISU) [6], to name a few, are investigating the potential of Dual-Rotor Wind Turbine (DRWT) systems due to its ability to extract more energy per tower. In addition, dual-rotor systems have the potential to lower the overall cost by reducing the number of towers which accounts for around 14%-17% of the total cost of the turbine including operation and management, grid connection, and foundation costs [7][8][9], albeit the need for stronger tower and more complex gearbox.…”

“…The RANS results showed a net increase of 7% in power coefficient can be obtained when the swept area of the secondary rotor is 25% that of the main rotor with a distance separating the rotors of 20% of the main rotor radius. Furthermore, Ozbay et al [6] conducted a wind tunnel investigation of DRWTs in either co-rotating or counter-rotating configuration using a model DRWT equipped with two 24 cm diameter rotors. It was found that the counter-rotating model which harvested approximately 7.8% more energy than the co-rotating model, and produced up to 60% more wind energy as compared with the SRWT model.…”