Analysis of Unsteady Flows Past Horizontal Axis Wind Turbine Airfoils Based on Harmonic Balance Compressible Navier-Stokes Equations With Low-Speed Preconditioning

M Sergio Campobasso,Mohammad H Baba-Ahmadi

doi:10.1115/1.4006293

M Sergio Campobasso, Mohammad H Baba-Ahmadi

Open Access

https://doi.org/10.1115/1.4006293

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Abstract

This paper presents the numerical models underlying the implementation of a novel harmonic balance compressible Navier-Stokes solver with low-speed preconditioning for wind turbine unsteady aerodynamics. The numerical integration of the harmonic balance equations is based on a multigrid iteration, and, for the first time, a numerical instability associated with the use of such an explicit approach in this context is discussed and resolved. The harmonic balance solver with low-speed preconditioning is well suited for the analyses of several unsteady periodic low-speed flows, such as those encountered in horizontal axis wind turbines. The computational performance and the accuracy of the technology being developed are assessed by computing the flow field past two sections of a wind turbine blade in yawed wind with both the time-and frequency-domain solvers. Results highlight that the harmonic balance solver can compute these periodic flows more than 10 times faster than its time-domain counterpart, and with an accuracy comparable to that of the time-domain solver.

Highlights

The aeromechanical design of horizontal axis wind turbines (HAWT’s) is a complex multidisciplinary task that requires consideration of a very large number of operating regimes due to the extreme variability of the environmental conditions on time scalesTURBO-10-1073, M.S
Modern industrial design still relies on low-fidelity and/or semi-empirical computational tools such as blade element momentum theory (BEMT), stall and dynamic inflow models [1]
Accurate time-dependent simulations of HAWT flows may still take several days, whereas the same engineering problem could be solved within a few hours using BEMT-based systems

Summary

Introduction

The aeromechanical design of horizontal axis wind turbines (HAWT’s) is a complex multidisciplinary task that requires consideration of a very large number of operating regimes due to the extreme variability of the environmental conditions on time scalesTURBO-10-1073, M.S. The wallclock time required by the TD NS prediction of unsteady periodic flows can be dramatically reduced by using a frequency-domain (FD) formulation and solution of the governing unsteady equations. The harmonic balance (HB) NS technology for the solution of unsteady periodic flows [6] is one of the most promising FD NS methods.

Results

Conclusion