Hybrid vortex simulations of wind turbines using a three‐dimensional viscous–inviscid panel method

Ramos‐García, Néstor; Hejlesen, Mads Mølholm; Sørensen, Jens Nørkær; Walther, Jens Honoré

doi:10.1002/we.2126

Cited by 29 publications

(54 citation statements)

References 28 publications

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“…Time ratios can vary from one computer system to another, and they depend on the number of blade elements/stations, enabled DOFs and other inputs that affect the number of calculations per time step, see, e.g., Section 4.1. In particular, MIRAS contains several parameters to control the computational speed and accuracy of the wake, which has not been investigated in the current study. Figure depicts the percent difference in torque and thrust relative to one‐to‐one coupling (left) and time ratios (right) versus the time step.…”

Section: Resultsmentioning

confidence: 99%

“…The accuracy of the loads computed on the rotor is dependent on the wake resolution, see Ramos‐García et al . and Ramos‐García et al . for details.…”

Section: Resultsmentioning

confidence: 99%

“…The MIRAS free‐wake model under varying conditions is depicted in Figures , and of this paper. A particle mesh implementation as described in is used in the current paper for improved computational efficiency. The MIRAS code is parallelized using message passing interface (MPI) software from Oracle Solaris Studio version 12.3.…”

Section: Description Of Miras and Flex5mentioning

confidence: 99%

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Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations

et al. 2017

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Aerodynamic and structural dynamic performance analysis of modern wind turbines are routinely estimated in the wind energy field using computational tools known as aeroelastic codes. Most aeroelastic codes use the blade element momentum (BEM) technique to model the rotor aerodynamics and a modal, multi‐body or the finite‐element approach to model the turbine structural dynamics. The present work describes the development of a novel aeroelastic code that combines a three‐dimensional viscous–inviscid interactive method, method for interactive rotor aerodynamic simulations (MIRAS), with the structural dynamics model used in the aeroelastic code FLEX5. The new code, called MIRAS‐FLEX, is an improvement on standard aeroelastic codes because it uses a more advanced aerodynamic model than BEM. With the new aeroelastic code, more physical aerodynamic predictions than BEM can be obtained as BEM uses empirical relations, such as tip loss corrections, to determine the flow around a rotor. Although more costly than BEM, a small cluster is sufficient to run MIRAS‐FLEX in a fast and easy way. MIRAS‐FLEX is compared against the widely used FLEX5 and FAST, as well as the participant codes from the Offshore Code Comparison Collaboration Project. Simulation tests consist of steady wind inflow conditions with different combinations of yaw error, wind shear, tower shadow and turbine‐elastic modeling. Turbulent inflow created by using a Mann box is also considered. MIRAS‐FLEX results, such as blade tip deflections and root‐bending moments, are generally in good agreement with the other codes. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

“…The accuracy of the loads computed on the rotor is dependent on the wake resolution, see Ramos‐García et al . and Ramos‐García et al . for details.…”

Section: Resultsmentioning

confidence: 99%

Section: Description Of Miras and Flex5mentioning

confidence: 99%

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Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations

et al. 2017

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“…MIRAS is a multi‐fidelity computational vortex model mainly used for predicting the aerodynamic behavior of wind turbines and its wakes. It has been developed at Technical University of Denmark (DTU) during the last decade, and it is extensively validated for small to large size wind turbine rotors by Ramos‐Garcia et al…”

Section: Methodology For Validationmentioning

confidence: 99%

“…To avoid the singular behavior of newly released vortex elements, an initial core radius,

ε_{0}

, is introduced. In accordance with Ramos‐Garcia et al, where it was found out that a small core radius is necessary to have flow convergence, a core radius of

0.1 %

local chord at the release station is used.…”

Section: Methodology For Validationmentioning

confidence: 99%

A simple improvement of a tip loss model for actuator disc simulations

et al. 2020

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The loading of a wind turbine decreases towards the blade tip because of the velocities induced by the tip vortex. This tip loss effect has to be taken into account when performing actuator disc simulations, where the single blades of the turbine are not modeled. A widely used method applies a factor on the axial and tangential loading of the turbine. This factor decreases when approaching the blade tip. It has been shown that the factor should be different for the axial and tangential loading of the turbine to model the rotation of the resulting force vector at the airfoil sections caused by the induced velocity. The present article contains the derivation of a simple correction for the tangential load factor that takes this rotation into account. The correction does not need any additional curve fitting but just depends on the local airfoil characteristics and angle of attack. Actuator disc computations with the modified tip loss correction show improved agreement with results from actuator line, free wake lifting line, and blade element momentum simulations.

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Vortex simulations of wind turbines operating in atmospheric conditions using a prescribed velocity‐vorticity boundary layer model

et al. 2018

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A prescribed velocity-vorticity boundary layer model for the vorticity transport equation is proposed, which corrects the unphysical upward deflection of the wake seen in a simpler prescribed velocity shear approach. A Lagrangian implementation of the boundary layer model has been investigated using our in-house vortex solver MIRAS. The MIRAS code contains both an aerodynamic part and a structural-mechanical part taking into account aeroelastic phenomena. The solver is employed to simulate flows around wind turbines and uses a combination of filaments and particles in order to mimic the vorticity released by the wind turbine blades. The vorticity is interpolated onto a uniform Cartesian mesh, where the interaction is efficiently calculated by an fast Fourier transform-based method. Simulations of wind turbines operating in an atmospheric boundary layer flow are carried out and analysed in detail for a range of scenarios. The manuscript focuses on studying the influence of wind shear and turbulence, which is varied to mimic natural atmospheric conditions. A traverse virtual probe up to 30 diameters downstream of the rotor plane is used to investigate the properties of the turbulent wake flow for the different cases.This includes mean and standard deviation of the streamwise velocity component, wake deficit, Reynolds stresses, and power spectral density of the velocity signal. The results show that combining a prescribed boundary layer approach with a vortex method gives consistent and physically correct results if properly implemented. KEYWORDS aeroelasticity, atmospheric boundary layer, turbulence, vortex method, wind shear, wind turbine INTRODUCTIONVortex methods initially entered the wind energy community as a more physically accurate alternative to the basic Blade Element Momentum method (BEM) technique, which is based on 1-dimensional momentum theory and aimed to be used for rotor design. However, vortex methods have quickly developed in recent years and now can be seen as an advanced and matured tool capable of performing high-fidelity simulations of 1 or more turbines. Vortex methods are not only of interest during the actual rotor design process but also as analysis tool to investigate more complex scenarios, including aeroelastic, turbulent inflow, and shear effects. [1][2][3][4][5][6] Vortex solvers can be combined with different aerodynamic models depending on the degree of complexity required. Enumerated in ascending complexity, they can be classified as lifting line (LL) vortex lattice, potential panel method, and viscous-inviscid panel method. The latter class being the more physically correct, since it resolves the actual geometry of the blade accounting for the viscous effects enclosed inside the boundary layer.The present paper focuses on the lower degree of fidelity in terms of aerodynamic modeling of the wind turbine blades, using the LL approach. With the LL model, the rotor blades are represented by discrete filaments, which account for the bound vortex strength and release vorticity into the ...

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Hybrid vortex simulations of wind turbines using a three‐dimensional viscous–inviscid panel method

Cited by 29 publications

References 28 publications

Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations

Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations

A simple improvement of a tip loss model for actuator disc simulations

Vortex simulations of wind turbines operating in atmospheric conditions using a prescribed velocity‐vorticity boundary layer model

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