Abstract
Abstract. We introduce an improved formulation of the double-multiple streamtube (DMST) model for the prediction of the flow quantities of vertical axis wind turbines (VAWT). The improvement of the new formulation lies in that it renders the DMST valid for any induction factor, i.e., for any combination of rotor solidity and tip speed ratio. This is done by replacing the Rankine–Froude momentum theory of the DMST, which is invalid for moderate and high induction factors, with a new momentum theory recently proposed, which provides sensible results for any induction factor. The predictions of the two DMST formulations are compared with VAWT power measurements obtained at Princeton's High Reynolds number Test Facility, over a range of tip speed ratios, rotor solidities, and Reynolds numbers, including those experienced by full-scale turbines. The results show that the new DMST formulation demonstrates a better overall performance, compared to the conventional one, when the rotor loading is moderate or high.
Highlights
The study of vertical axis wind turbines (VAWTs) has received renewed attention in the last decade
double-multiple streamtube (DMST) algorithms are known to fail to accurately capture the local aerodynamic loads on the rotor (Wilson and McKie, 1980; Ferreira et al, 2014); still, their “global” or mean predictions are of significant accuracy, and as a result DMST remains a popular tool in VAWT design protocols
The above facility permitted the attainment of dynamic similarity in the current experiment, by simultaneously matching the Reynolds number, tip speed ratio, and Mach number of the VAWT lab-scale models with those encountered in full-scale VAWTs
Summary
The study of vertical axis wind turbines (VAWTs) has received renewed attention in the last decade. Such treatment of the rotor fails to model other important aspects of the flow physics: DMST assumes zero expansion of the streamtubes, and it neglects the wake– blade interaction and the effect of the downstream half of the rotor on the upstream half For these reasons, DMST algorithms are known to fail to accurately capture the local aerodynamic loads on the rotor (Wilson and McKie, 1980; Ferreira et al, 2014); still, their “global” or mean predictions are of significant accuracy, and as a result DMST remains a popular tool in VAWT design protocols.
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