# Evaluation of Tip Loss Corrections to AD/NS Simulations of Wind Turbine Aerodynamic Performance
## 1 Introduction
The question is whether a tip loss correction has a good global performance when it is transplanted into AD/NS. Even for the BEMT itself, evaluations indicate that accurate tip loss correction is still not well achieved [27], and the development of new correction models is still going on [28; 29; 30; 31; 32; 33]. In contrast with the massive study in the BEMT, tip loss corrections applied to AD/NS lack a comprehensive evaluation. In the present work, the 2-Dimensional (2D) axisymmetric AD model is employed, and steady-state simulations are performed. The code solves the incompressible axisymmetric NS equations for the experimental _NREL Phase VI_ wind turbine [34] and the virtual _NREL 5 MW_[35] wind turbine under various axial inflow conditions. The main purpose of the numerical study is to evaluate the performance of the tip loss corrections applied to AD/NS. Three different implementations of the Glauert tip loss correction are discussed. In addition, a new tip loss correction recently proposed by [PERSON] et al. [33] is introduced and compared. The normal and tangential forces of blade cross-sections are chosen as the key parameters for the present evaluation. Because of the long arm of force, computational errors of the forces acted on the tip region are most likely to cause non-ignorable errors of the blade bending moment and the rotor torque (power generation). A BEMT study on the _NREL Phase VI_ wind turbine by [PERSON] [27] showed that the power generation would be overestimated by 15% if no tip loss correction was made and a deviation of about 5% exists when various existing tip loss corrections were applied. That highlights the significance of the present study on tip loss correction. The innovation of the present study lies in the following items. (a) Different implementations of the Glauert tip loss factor \(F\) are gathered, discussed and compared, and finally, one of them is recommendedaccording to its best performance. Such kind of work has never been reported in the existing literature. (b) The Glauert correction is found to have a similar performance when it is transplanted from BEMT to AD/NS. (c) The new tip loss correction of [PERSON] et al. [33] is for the first time employed in AD/NS simulations. It is found to be generally superior to the Glauert-type corrections. That provides an alternative choice for a more accurate prediction of the blade tip loads. (d) Tip loss correction is found to have a significant influence on the velocity field, which highlights the importance of an accurate tip loss correction for not only the blade loads, but also the wake development. The paper is organized as follows: In Section 2, the axisymmetric AD/NS method is introduced, including the governing equations of the NS approach and the formulae of the AD model; In Section 3, the Glauert and the new tip loss corrections are introduced; In Section 4, the implementations of the tip loss corrections used in AD/NS are described; In Section 5, the numerical setup, as well as the involved simulation cases, are introduced; In Section 6, all simulation results are presented and discussed; Final conclusions are made in the last section.