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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
Assessment of the Elliptic Blending RSM Turbulence Model on a Wind Turbine-Type Rotor Under Mildly Compressible Blade Tip Flow Regime
Submission Author:
Marco Leonardelli Lovatto , RS
Co-Authors:
Marco Leonardelli Lovatto, Adriane Prisco Petry
Presenter: Marco Leonardelli Lovatto
doi://10.26678/ABCM.ENCIT2020.CIT20-0640
Abstract
Large multi-megawatt horizontal axis wind turbines (HAWTs) may encounter mildly compressible flow regimes at the suction side of the blade tip, a phenomenon that should be assessed with caution by using CFD strategies capable of capturing it, especially if blade tip vortices, aeroelasticity and aeroacoustics are of interest. This work aims to stimulate the development of such strategies as high-fidelity references for the improvement of low-fidelity (engineering) models, such as Blade Element Momentum (BEM) and Vortex Wake Models (VWM). Differently from two-equation turbulence models, which generally rely on the assumption of isotropic turbulence, the anisotropic characteristics of Reynolds Stress Models (RSM) offer the potential of capturing more of the complex flow phenomena intrinsic of rotating systems. A literature research suggests that this is the first work to assess the EB-RSM (Elliptic Blending RSM), an RSM with low-Reynolds modeling capabilities, on a wind turbine-type rotor under a mildly compressible blade tip flow regime. The results for blade pressure profiles, sectional loads, axial force (thrust) and torque obtained from the steady-state EB-RSM are compared to the reference experimental measurements offered by the New MEXICO campaign, as well as to other CFD data from recent literature. This research includes a Grid Convergence Index (CGI) study and is performed using the commercial multiphysics software Simcenter STAR-CCM+. This work focuses on the unyawed 4.5 m diameter three-bladed MEXICO rotor with -2.3º blade pitch angle rotating at 425.1 rpm under the design free-stream velocity of 15.06 m/s, resulting on a tip speed ratio (TSR) of 6.65, where velocity magnitudes as high as 140 m/s (Mach 0.4) are attained on the suction side of the blade near the tip, with respect to the rotating reference frame, a condition expected to be found in large HAWTs. Grid-converged results obtained on a 6.5 million cell polyhedral mesh delivered pressure loads comparable to the values obtained by other researchers. As an additional output, the authors induce that the loads including skin friction, obtained from continuous integration using mesh resolution, may be considered as a possible reference for the calibration of low-fidelity wind turbine engineering models.
Keywords
Computational fluid dynamics (CFD), Aerodynamics, wind energy, Turbomachinery, all-Mach coupled flow
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