Aerodynamic Design Optimization on Unstructured Meshes Using the Navier-Stokes Equations

Eric, J Nielsen; Kyle, Anderson W.

doi:10.2514/2.640

Cited by 218 publications

(113 citation statements)

References 49 publications

(41 reference statements)

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“…Examples of these are, turbulent models, flux limiters, reconstruction operator for higher order accuracy, model parameters of the convective schemes etc. Jacobian approximations may result in inaccurate computation of sensitivities [19]. In fact, in unsteady flows, the effect of these approximations on the accuracy of sensitivities is much more significant as the errors generated in the adjoint solution tend to accumulate rapidly while solving the adjoint equations backward-in-time [16].…”

Section: Introductionmentioning

confidence: 99%

A Two-Level Hybrid Approach for Optimal Active Flow Control on a Three-Element Airfoil

Nemili¹,

Özkaya²,

Gauger³

et al. 2016

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)

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Abstract. In this paper we present a two-level approach that combines an adjoint-based gradient search method with an evolutionary algorithm for optimal active flow control. The suggested method effectively combines the advantages of both approaches and achieves a good compromise between the computational effort and the degree of freedom used in optimization. In the first level, a global optimization is performed with few design parameters using an evolutionary algorithm. In the second level, the global optimal solution from the first level is taken as the initial setting for the adjoint based local optimization using a large number of design parameters. The unsteady discrete adjoint solver required for the second level is developed based on Algorithmic Differentiation techniques for the unsteady incompressible flowsgoverned by Unsteady Reynolds-Averaged Navier Stokes (URANS) equations. In this way, the discrete adjoint solver is robust and has exactly the same functionality with the underlying URANS flow solver. The applicability of the two-level method is demonstrated by finding the optimal parameters of the active flow control mechanism on a three element airfoil configuration at a Reynolds number of Re = 10 6 and an angle of attack of AoA = 6 • . Numerical results have shown that the hybrid approach completely suppressed the separation and very significantly increased the mean-lift coefficient by 67% compared to the un-actuated baseline flow.

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Section: Introductionmentioning

confidence: 99%

A Two-Level Hybrid Approach for Optimal Active Flow Control on a Three-Element Airfoil

Nemili¹,

Özkaya²,

Gauger³

et al. 2016

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)

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“…For more information on FUN3D see Anderson and Bonhaus 29 or Nielsen. 30 The steady RANS equations are closed with the Menter 31 Shear Stress Transport (SST) turbulence model. Because the nozzle is axisymmetric and the ground is not specified as a boundary condition in the CFD calculation, the resultant steady flowfield is axisymmetric.…”

Section: The Steady Rans Solutionmentioning

confidence: 99%

The Prediction of Jet Noise Ground Effects using an Acoustic Analogy and a Tailored Green’s Function

Miller

2013

19th AIAA/CEAS Aeroacoustics Conference

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An assessment of an acoustic analogy for the mixing noise component of jet noise in the presence of an infinite surface is presented. The reflection of jet noise by the ground changes the distribution of acoustic energy and is characterized by constructive and destructive interference patterns. The equivalent sources are modeled based on the two-point crosscorrelation of the turbulent velocity fluctuations and a steady Reynolds-Averaged NavierStokes (RANS) solution. Propagation effects, due to reflection by the surface and refraction by the jet shear layer, are taken into account by calculating the vector Green's function of the linearized Euler equations (LEE). The vector Green's function of the LEE is written in relation to Lilley's equation; that is, approximated with matched asymptotic solutions and the Green's function of the convective Helmholtz equation. The Green's function of the convective Helmholtz equation for an infinite flat plane with impedance is the Weyl-van der Pol equation. Predictions are compared with an unheated Mach 0.95 jet produced by a nozzle with an exit diameter of 0.3302 meters. Microphones are placed at various heights and distances from the nozzle exit in the peak jet noise direction above an acoustically hard and an asphalt surface. The predictions are shown to accurately capture jet noise ground effects that are characterized by constructive and destructive interference patterns in the mid-and far-field and capture overall trends in the near-field.

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“…This approach increases the efficiency of the method in terms of required CPU-time, with respect to handling the adjoint vectors sequentially. The method was tested for a similar case as the drag minimization problem of a wing in transonic flow presented by Nielsen [130], also using an ONERA M6 wing as starting geometry.…”

Section: Related Workmentioning

confidence: 99%

“…Nielsen implemented the discrete adjoint equation method in an unstructured RANS method [130]. The solution of the adjoint equations was subsequently used for determining the sensitivities for various optimization problems.…”

Section: Related Workmentioning

confidence: 99%

“…In these models averaging of the flow variables is performed, in such a way that unsteady effects due to turbulence are eliminated from the result, but its influence on mean flow variables is modelled. Aerodynamic optimization methods have been developed for which the flow model is based on a RANS turbulence model [53,115,130]. For the present work however, the Euler equations are used to model the flow.…”

Section: Flow Modelmentioning

confidence: 99%

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O a method for simulation-based wind turbine blade design

Jongsma¹

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SummaryW ind turbines are an important means for the production of renewable energy. This energy, commonly referred to as wind energy, is produced by extracting the kinetic energy from the wind and to subsequently convert it, usually via a rotational motion, to electrical energy. Wind conditions vary from one site to another and the design of a horizontal axis wind turbine depends on these local wind conditions. One of the important aspects of the design of a wind turbine concerns the aerodynamic shape of the rotor blades. The research presented in this thesis focusses on the development of a computational method that can be used for aerodynamic shape optimization.Other aspects -apart from the aerodynamic shape of a wind turbine rotor bladeare also important in the design of a wind turbine, for instance the structural design of the blade. To take this multidisciplinary character of wind turbine design into account, one of the aims of the research presented in this thesis has been that the aerodynamic shape optimization method seamlessly fits into the design process. Moreover, the optimization method is required to be efficient and fully automatic.A suitable method for the parametrization of the wind turbine blade geometry has been investigated. This investigation lead to the choice to use a non-uniform rational basis spline (NURBS) surface for representing the aerodynamic shape of the wind turbine blade. Such a description of the parametrization of the geometry is compatible with computer aided design methods, which eases the incorporation of the aerodynamic shape optimization method in the multidisciplinary design process. A model optimization problem has been considered to determine the relation between the number of design variables that is required to sufficiently accurately represent the design space for solving an aerodynamic shape optimization problem to the number of design variables that is required to realize an accurate NURBS representation of an aerodynamic shape. For the purpose of obtaining a NURBS surface representation of a wind turbine rotor blade, a fitting procedure has been developed. The accuracy of the resulting fit for two representative wind turbine blades is presented. It has been found that sufficient accuracy can be achieved with a NURBS surface described by 13 chordwise sections with 13 control points each.In the present research, objective functions are considered for which the evaluation requires the solution of partial differential equations that govern flow: the Euler equations. Since only for very particular flow configurations an analytical solution of these equations can be found, an approximate solution is computed by solving the discretized equations. Solving the discretized Euler equations requires the discretization of the whole flow domain. During the optimization procedure, the geometry of the rotor blade adapts, i Summary requiring a discrete representation of the new flow domain. To accommodate the change in shape during the optimization, a hyperbolic grid generation me...

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Aerodynamic Design Optimization on Unstructured Meshes Using the Navier-Stokes Equations

Cited by 218 publications

References 49 publications

A Two-Level Hybrid Approach for Optimal Active Flow Control on a Three-Element Airfoil

A Two-Level Hybrid Approach for Optimal Active Flow Control on a Three-Element Airfoil

The Prediction of Jet Noise Ground Effects using an Acoustic Analogy and a Tailored Green’s Function

O a method for simulation-based wind turbine blade design

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