PIV measurements and CFD simulation of the performance and flow physics and of a small‐scale vertical axis wind turbine

Abstract

The aerodynamics generated by a small small-scale vertical axis wind turbine (VAWT) are illustrated in detail as a NACA0022 rotor blade carries out a complete rotation at three tip speed ratios. These aerodynamic details are then linked to the wind turbine performance. This is achieved by using detailed experimental measurements of performance and near blade PIV and also using a 2D RANS based CFD model. Uniquely therefore, the CFD model is validated against both PIV visualisations and performance measurements.At low tip speed ratios ( = 2), the flow field is dominated by large scale stalling behaviour as shown in both the experimental results and simulations. The onset of stall appears to be different between the experiment and simulation, with the simulation showing a gradual separation progressing forwards from the trailing edge, while the experiment shows a more sudden leading edge roll-up. Overall, similar scales of vortices are shed at a similar rate in both. The most significant CFD-PIV differences are observed in predicting flow reattachment. At a higher tip speed ratio ( = 3), the flow separates slightly later than in the previous condition and as occurs in the lower tip speed ratio, the main differences between the experiment and the simulation are in the flow reattachment process, specifically that the simulations predicts a delay in the process. At a tip speed ratio of 4, smaller predicted flow separation in the latter stages of the upwind part of the rotation is the main difference in comparison to the experiment.

A comprehensive review of the theoretical approaches for the airfoil design of lift-type vertical axis wind turbine

“…Many researchers have conducted the CFD simulation on the VAWTs recently [4,86]. Table 1 presents a brief review of CFD researches [26,54,76,87,88] which were compared with the experimental results.…”

“…Generally, research topics or established practice for a specific class of problem determine the requirements of computational time, accuracy and cost resources [90]. And the requirements of computational time and accuracy decide the adoption of CFD simulation strategies [86]. The research topics of the airfoil design can be airfoil aerodynamic research and the effect of airfoil geometry on the performance.…”

“…The performance of VWT was predicted accurately. The postprocedure is to analyze the output of the monitoring flow properties [95] or flow field [86]. The analyzed results offer guidance for the further optimization of the geometry.…”

“…Each step of this process is operated manually. Thus, this process, most of the time, is used for cases which have complicated geometry [96] or were not aimed at the parametrical study [86]. The greatest disadvantage of this common process is that users need to modify the geometry, generate the mesh, choose the simulation settings and analyze the results manually when design parameters are changed.…”

Vertical axis wind turbine in a falling soap film

“…A reasonable approach is to first decouple the problem and develop an understanding of the flow around an individual VAWT. Much of the recent experimental work related to VAWTs has focused on blade-level aerodynamics, such as dynamic stall and tip vortex shedding, [5][6][7] as well as near wake analysis of the mean flow and Reynolds stresses. 6,8 Motivated by a desire to develop intuition about the spatio-temporal evolution of the VAWT wake, we constructed a qualitative flow visualization experiment using a miniature, 3-bladed VAWT in a gravity-driven soap film tunnel (Fig.…”