Reverse Flow Dynamic Stall Modelling for HAWTs
B. Sanchez Diaz (TU Delft - Aerospace Engineering)
D. Ragni – Mentor (TU Delft - Aerospace Engineering)
M. Kotsonis – Graduation committee member (TU Delft - Aerospace Engineering)
D.A.M. De Tavernier – Graduation committee member (TU Delft - Aerospace Engineering)
Valentina Motta – Mentor (General Electric Renewables)
Marianne Hartung – Mentor (General Electric Renewables)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Forward flow dynamic stall is a heavily researched field with multiple well-established models that appropriately capture this type of flow at moderate angles of attack. However, horizontal axis wind turbines operate at a wide range of angles of attack and rapidly changing wind directions, conditions for which limited literature studying the performance of these models has been found. An especially under-researched field is reverse flow dynamic stall, both in terms of experimental investigation and modelling. Therefore, the purpose of this research is to identify the relevant flow phenomena occurring in reverse flow and to analyze which dynamic stall models can accurately represent these flow conditions.
The performance of established dynamic stall models such as the one developed by Pierce and the current General Electric dynamic stall model (GE2021) was assessed in reverse flow conditions. In addition, improvements to the GE2021 model were proposed to enhance its performance, including a delay in the effective angle of attack as a function of the reduced frequency and the addition of vortex effects in the load calculation. Three options for the inclusion of vortex effects were explored. The first used the formulation of vortex effects developed by Pierce, which, being very similar to those proposed in the original Beddoes-Leishman model, allows assessment of the performance of the latter for reverse flow dynamic stall. The second focused on the interpretation proposed by Sheng, Galbraith, and Coton of the vortex effects calculation formulated by Beddoes. The last consisted of a simplification of the sinusoidal vortex effects computation of the second approach. In addition, study and tuning of the variables and coefficients involved in this calculation were developed in order to provide a versatile model with the ability to provide reliable results in both forward and reverse flow conditions.
This project aims to be a first step in the study of reverse flow modelling and to improve our understanding of its modelling requirements.