Abstract
Accurate prediction of power generation capability needs proper assessment of blade loading and wake behavior. In this regard, the Sliding Mesh Interface (SMI) approach and the Actuator Line Model (ALM) are two diverse computational fluid dynamics (CFD) based approaches of simulating the turbine behavior, each having its own merits and demerits. The SMI technique simulates the unsteady flow by explicitly modeling the blades and their rotation using a dynamic mesh, while in Actuator Line Model, the blades are not modeled explicitly but each blade is resolved as a rotating line (made of N actuator segments), over which the forces are computed. The current work focuses on simulating an industrial scale reference turbine and in differentiating the near wake dynamics predicted by these two approaches using Large Eddy Simulation (LES) and Proper Orthogonal Decomposition (POD) technique (a data mining tool). Initially, the ALM is compared with FAST model for the prediction of variation of power coefficient with the Tip Speed Ratio (TSR). The ALM is able to capture the varying trend and it predicts a similar optimum tip speed ratio as the FAST model. At this optimum TSR condition, the ALM is compared with the SMI method for a study limited to the near wake region. Comparisons between SMI and ALM shows that : (a) The SMI is predicting more complex 3D nature of the flow, and (b) the POD shows that ALM captures the shear regions of wake but it does not capture the vast compendium of length and time scales of eddies as SMI does. However, despite these limitations, the ALM has been able to capture the qualitative trend in wake deficit and the power coefficient variation with tip speed.
Highlights
Introduction and objectiveWake dynamics have been shown to influence the power production capabilities of downstream turbines depending upon the inter-turbine distance in a wind farm layout [1,2,3,4,5]
The Actuator Line Model (ALM) is compared with FAST model for the prediction of variation of power coefficient with Tip Speed Ratio (TSR)
Conclusion and future work The paper aims to use Large Eddy Simulation (LES) and Proper Orthogonal Decomposition (POD) technique to differentiate wake dynamics captured by two diverse methods (ALM and Sliding Mesh Interface (SMI) techniques) for an industrial scale wind turbine
Summary
Introduction and objectiveWake dynamics have been shown to influence the power production capabilities of downstream turbines depending upon the inter-turbine distance in a wind farm layout [1,2,3,4,5]. Actuator Line Model (ALM) with Large Eddy Simulation (LES) turbulence model has been used popularly to understand the wake dynamics in wind farms as it is computationally tractable to do so for multi-turbine set-ups. It is well-known that ALM does not explicitly resolve turbine blades and might not be expected to be accurate enough. The Sliding Mesh Interface (SMI) approach resolves the blade and is expected to be more accurate but it is computationally intractable to perform for a set-up with multiple turbines
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