Integrated Design of an Active Flow Control System Using a Time-Dependent Adjoint Method

Nielsen, Eric J.; Jones, William T.

doi:10.1051/mmnp/20116306

Cited by 24 publications

(18 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In general, a discrete adjoint solver for optimal active flow control can be developed either by using the so-called hand-discrete approach [14] or by employing Algorithmic Differentiation (AD) techniques [15,16]. In the hand-discrete approach, the governing flow equations are first discretized as usual.…”

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)

View full text Add to dashboard Cite

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.

show abstract

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)

View full text Add to dashboard Cite

show abstract

“…FUN3D also offers a discretely-consistent adjoint implementation that has been used to perform mathematically-rigorous design optimization, error estimation, and formal mesh adaptation for complex geometries and flow-fields in massively parallel computing environments. 13,24 These applications include accurate analysis and design optimization of aircraft concepts aimed at sonic boom mitigation.…”

Section: Coupled Cfd/boom Adjoint Formulationmentioning

confidence: 99%

Sonic-Boom Mitigation Through Aircraft Design and Adjoint Methodology

Rallabhandi

Nielsen

Diskin

2014

Journal of Aircraft

View full text Add to dashboard Cite

This paper presents a novel approach to design of the supersonic aircraft outer mold line (OML) by optimizing the A-weighted loudness of sonic boom signature predicted on the ground. The optimization process uses the sensitivity information obtained by coupling the discrete adjoint formulations for the augmented Burgers Equation and Computational Fluid Dynamics (CFD) equations. This coupled formulation links the loudness of the ground boom signature to the aircraft geometry thus allowing efficient shape optimization for the purpose of minimizing the impact of loudness. The accuracy of the adjoint-based sensitivities is verified against sensitivities obtained using an independent complex-variable approach. The adjoint based optimization methodology is applied to a configuration previously optimized using alternative state of the art optimization methods and produces additional loudness reduction. The results of the optimizations are reported and discussed.

show abstract

“…The adjoint equations can be dealt with either in discrete or continuous form (Giles & Pierce 2000). Discrete adjoint methods have been implemented in design optimisations by Homescu, Navon & Li (2002); Jones (2011) andNielsen, Diskin &Yamaleev (2010). However, the discrete adjoint equations are dependent on the discretization method and the grid and therefore cannot be generalized easily.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear optimal suppression of vortex shedding from a circular cylinder

2015

View full text Add to dashboard Cite

This study is focused on two-and three-dimensional incompressible flow past a circular cylinder for Re ≤ 1000. To gain insight into the mechanisms underlying the suppression of unsteadiness for this flow we determine the nonlinear optimal open-loop control driven by surface-normal wall transpiration. The spanwise-constant wall transpiration is allowed to oscillate in time although steady forcing is determined to be most effective. At low levels of control cost, defined as the square integration of the control, the sensitivity of unsteadiness with respect to wall transpiration is a good approximation of the optimal control. The distribution of this sensitivity suggests that the optimal control at small magnitude is achieved by applying suction upstream of the upper and lower separation points and blowing at the trailing edge. At high levels of wall transpiration the assumptions underlying the linearised sensitivity calculation become invalid since the base flow is eventually altered by the size of the control forcing. The large magnitude optimal control is observed to spread downstream of the separation point, draw the shear layer separation towards the rear of the cylinder through suction while blowing along the centreline eliminates the recirculation bubble in the wake. We further demonstrate that it is possible to completely suppress vortex shedding in two-and three-dimensional flow past a circular cylinder up to Re = 1000, accompanied by 70% drag reduction when a nonlinear optimal control of moderate magnitude (with root mean square value 8% of the free stream velocity) is applied. This is confirmed through linearised stability analysis about the steady state solution when the nonlinear optimal wall transpiration is applied. While continuously distributed wall transpiration is not physically realisable, the study highlights localised regions where discrete control strategies could be further developed. It also highlights the appropriate range of application for linear and nonlinear optimal control to this type of flow problem.

show abstract

Integrated Design of an Active Flow Control System Using a Time-Dependent Adjoint Method

Cited by 24 publications

References 53 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

Sonic-Boom Mitigation Through Aircraft Design and Adjoint Methodology

Nonlinear optimal suppression of vortex shedding from a circular cylinder

Contact Info

Product

Resources

About