A transition prediction method for flow over airfoils based on high-order dynamic mode decomposition

Wu, M.; Han, Zhonghua; Nie, Han; Song, Wenping; Clainche, Soledad Le; Ferrer, Esteban

doi:10.1016/j.cja.2019.03.020

Cited by 35 publications

(10 citation statements)

References 37 publications

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“…In this case, the flow transitions at points x/c = 0.31 and x/c = 0.52 in the upper and lower surfaces, respectively. This result is in good agreement with experiments [12,13], that predict the transition points at x/c -0.35 -0.40 and x/c -0.5 -0.55 for the upper and lower surfaces, respectively.…”

Section: Transition Point In a Two-dimensional Airfoilsupporting

confidence: 92%

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An alternative method to calculate cross-flow instabilities

Clainche

Han

et al. 2018

2018 Fluid Dynamics Conference

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This work presents a new method to compute instabilities associated to cross-flow transition scenarios. The method analyses base flows issued from CFD simulations (RANS model) using higher order dynamic mode decomposition (HODMD). The flow field is then approximated as an expansion of modes and it is possible to identify the primary and secondary flow instabilities, in cross-flows. The good performance of this novel method is first validated by locating the transition point related to the first instability in a low-speed 2D NLF0416 airfoil. Then, 3D cross-flow instabilities over a wing with 40° back-sweep angle (shaped from a NACA642A015 airfoil) are presented.

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Section: Transition Point In a Two-dimensional Airfoilsupporting

confidence: 92%

“…The figure shows the N-factor related to each one of these flow instabilities. As seen, in the experimental results, presented in [12,13], the flow transition occurs for N -9. In this case, the flow transitions at points x/c = 0.31 and x/c = 0.52 in the upper and lower surfaces, respectively.…”

Section: Transition Point In a Two-dimensional Airfoilmentioning

confidence: 55%

An alternative method to calculate cross-flow instabilities

Clainche

Han

et al. 2018

2018 Fluid Dynamics Conference

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“…Numerical simulations are converged until the steady state is reached, which is defined when the maximum relative averaged-density residual is below 10 −6 . In previous work, 48 we addressed the effect of the residual, in the dominant spanwise mode, to find that the influence is minimal once the residual is below 10 −5 . These steady states exist only because we fix the transition line at x/c = 0.6, which is located after the "real" transition point.…”

Section: A the Idea Behind The Methodsmentioning

confidence: 99%

“…In Wu et al, 48 we proposed a similar DMD based transition prediction method for two-dimensional airfoils (governed by TS waves only) that we extend here to three-dimensional configurations and cross-flow scenarios. In that work, we compared our new method to linear stability theory (LST) using the e N criterion and experimental data for flows over two-dimensional airfoils.…”

Section: Introductionmentioning

confidence: 99%

An alternative method to study cross-flow instabilities based on high order dynamic mode decomposition

2019

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We present a novel method for the determination of N-factors in cross-flow transition scenarios. The method considers numerical simulations, in which a turbulent model is applied downstream from a predetermined point and solves a laminar flow upstream from this point. The solution is postprocessed using higher order dynamic mode decomposition to extract the leading spatial mode in several small sections along the streamwise direction. The spatial evolution of the amplitude of this mode will determine the N-factor. The results presented are compared with experimental measurements and linear stability theory, showing the good performance of this novel method, which does not assume parallel flow assumptions, is automatic and computationally efficient.

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“…The surrogate-based optimization refers to a method which uses surrogate models to replace time-consuming flow solvers, and refines the surrogate models by adding new sample points according to certain infill-sampling criteria, until the resulting "sequence of sample points" converges to the optimal solution. This method is proven to be efficient and robust, and more details about this method are presented in References [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58]. The optimization process was as follows:…”

Section: Design Optimizatoin Methodsmentioning

confidence: 99%

Design Optimization of a Multi-Megawatt Wind Turbine Blade with the NPU-MWA Airfoil Family

Han

Yan

et al. 2019

Energies

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A new airfoil family, called NPU-MWA (Northwestern Polytechnical University Multi-megawatt Wind-turbine A-series) airfoils, was designed to improve both aerodynamic and structural performance, with the outboard airfoils being designed at high design lift coefficient and high Reynolds number, and the inboard airfoils being designed as flat-back airfoils. This article aims to design a multi-megawatt wind turbine blade in order to demonstrate the advantages of the NPU-MWA airfoils in improving wind energy capturing and structural weight reduction. The distributions of chord length and twist angle for a 5 MW wind turbine blade are optimized by a Kriging surrogate model-based optimizer, with aerodynamic performance being evaluated by blade element-momentum theory. The Reynolds-averaged Navier-Stokes equations solver was used to validate the improvement in aerodynamic performance. Results show that compared with an existing NREL (National Renewable Energy Laboratory) 5 MW blade, the maximum power coefficient of the optimized NPU 5 MW blade is larger, and the chord lengths at all span-wise sections are dramatically smaller, resulting in a significant structural weight reduction (9%). It is shown that the NPU-MWA airfoils feature excellent aerodynamic and structural performance for the design of multi-megawatt wind turbine blades.Energies 2019, 12, 3330 2 of 24 designed by National Aeronautical Research Institute of Sweden [10]. The Northwestern Polytechnical University (NPU) of China has developed a family of NPU-WA (Northwestern Polytechnical University Wind-turbine A-series) airfoils for megawatt wind turbines, featuring a high lift-to-drag ratio at a high Reynolds number and a high lift coefficient [11][12][13][14]. The Chinese Academy of Sciences (CAS) has designed a family of CAS airfoils for medium Reynolds numbers [15]. The Chongqing University of China and Technical University of Denmark have developed the CQU-DTU-series airfoils, taking into account of the aerodynamic performance and low noise requirements [16]. Compared with the conventional aeronautic airfoils, the dedicated airfoils for wind turbine blades have a higher lift-to-drag ratio, which means that the aerodynamic force of the blades has a larger component in the tangential direction of the wind wheel and lower component in the axial direction (thrust), resulting in smaller thrust with the same tangential component of aerodynamic force, thus the total aerodynamic load is reduced.With the continuous development of wind turbine technology, the wind turbine generator system tends to become larger and larger. The blade diameter of wind turbines has increased from about 20 m in the 1980s to nearly 200 m, or even more now. Meanwhile, the capacity has also been increased, from 20 kW~60 kW to 5 MW~10 MW [17][18][19]. In recent years, the technology for applying the wind turbine-dedicated airfoil family to megawatt wind turbines (1.0 MW, 3.0 MW) has gradually matured. More and more attention has been paid to the development of new airfoil families dedicated t...

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A transition prediction method for flow over airfoils based on high-order dynamic mode decomposition

Cited by 35 publications

References 37 publications

An alternative method to calculate cross-flow instabilities

An alternative method to calculate cross-flow instabilities

An alternative method to study cross-flow instabilities based on high order dynamic mode decomposition

Design Optimization of a Multi-Megawatt Wind Turbine Blade with the NPU-MWA Airfoil Family

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