Abstract
Cross-flow hydrokinetic turbines have sparked interest among fluid dynamicists for their potential for power enhancement in paired configuration. Following the first part of a laboratory-scaled turbine wake measurement project, this second part presents a monoscopic particle image velocimetry measurement of the near-wake of two cross-flow hydrokinetic turbines in six different counter-rotating configurations. The turbines operated in a small water flume at an average diameter-based Reynolds number of 2×104 with the incoming streamwise velocity of 0.316 m/s. The six configurations included two turbine separation distances, two turbine phase angles differences, and two different relative incoming flow angles. Similar to the observation of the single turbine configurations in part I, a correlation between flow field structures and the corresponding power output was observed. Effects of each parameter of the counter-rotating configurations are further discussed, which suggest guidelines for setting up multiple devices in a power farm. This article is accompanied by all full numeric data sets and videos of the results.
Highlights
Counter-rotating configurations of vertical-axis turbines have been known to produced higher power per unit of land and water surface occupied
As early as 2011, John Dabiri performed a wind farm power measurement of vertical-axis wind turbines (VAWTs) in pairs and observed a potential order-of magnitude of power output enhancement compared to similar size horizontal-axis wind turbines [1]
Jiang et al later implemented a deflector between a pair of similar VAWTs and observed a 38.6% increase in the system power output [3]
Summary
Counter-rotating configurations of vertical-axis turbines have been known to produced higher power per unit of land and water surface occupied. In 2019, Dabiri group conducted experiments of a pair of vertical-axis turbines in a wind tunnel at the Reynolds number of 7.3 × 104 and recorded up to a 14% enhancement of array power performance [2]. Tow tank experiments were conducted by Wosnik group for a reference cross-flow hydrokinetic turbine [6,7]. Related to this reference model, Ross and Polagye performed various experimental measurements with other smaller scaled turbine models to assess analytically models of blockage effect on cross-flow turbines [8]. The near-wakes of six counter-rotating configurations were captured by the monoscopic particle image velocimetry (PIV) setup descried in Part I [11]
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