Adjoint-Based Aerodynamic Shape Optimization of Rotorcraft Blades

Nadarajah, Siva; Tatossian, Charles

doi:10.2514/6.2008-6730

Cited by 10 publications

(2 citation statements)

References 15 publications

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“…There are also two distinct flow regimes, hover and forward flight, and good performance in one is unlikely to be carried over to the other. Aerodynamic optimisation has been applied previously to rotors in hover but mainly with both low fidelity aerodynamics and only gross geometric changes, see for example (13) , with only a few notable results using compressible CFD, namely those of ONERA (14,15) , Nadarajah et al (16) , Choi et al (17) , Nielsen et al (18) , Imiela (19,20) , and recent work of Johnson and Barakos (21,22) . The research presented here is aimed at the development of a modularised, generic optimisation tool, that is flow-solver and mesh type independent, and applicable to any aerodynamic problem; rotor blades in hover in this case.…”

Section: Interpolation Formulationmentioning

confidence: 99%

Aerodynamic shape optimisation of hovering rotors using compressible CFD

Allen

Rendall²

2011

Aeronaut. j.

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Generic wrap-around shape optimisation technology is presented, and is applied to a helicopter rotor in hover, using compressible CFD as the aerodynamic model. An efficient domain element shape parameterisation method is used as the surface control and deformation method, and is linked to a radial basis function global interpolation, to provide direct transfer of domain element movements into deformations of the design surface and the CFD volume mesh. This method is independent of mesh type and size, and optimisation independence from the flow solver is achieved by obtaining sensitivity information for an advanced parallel gradient-based algorithm by finite-difference. The method is applied here to a two-bladed hovering rotor, with transonic tip speed, comparing the effects of global twist parameters and more local planform parameters. Significant torque reductions are achieved in both cases, and it is shown that using only three global twist parameters are extremely effective. Using 63 local and global parameters, large geometric changes are demonstrated, with both induced power and wave drag reduced.

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Section: Interpolation Formulationmentioning

confidence: 99%

Aerodynamic shape optimisation of hovering rotors using compressible CFD

Allen

Rendall²

2011

Aeronaut. j.

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“…Other similar approaches, such as the Nonlinear Frequency Domain [3,4,5], Reduced Frequency [6], and Time-Spectral [7,8,9] methods, were developed shortly thereafter. Additionally, adjoint-based optimization techniques [10,11] can be applied to provide the ability to perform design optimization without resorting to costly unsteady adjoint methods. Frequency-adaptive methods [12,13,14] can o↵er even greater e ciency by refining the the number of modes resolved at each grid point to the frequency content in its solution.…”

Section: Introductionmentioning

confidence: 99%

An Extension of the Time-Spectral Method to Overset Solvers

Leffell

Murman

Pulliam

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Relative motion in the Cartesian or overset framework causes certain spatial nodes to move in and out of the physical domain as they are dynamically blanked by moving solid bodies. This poses a problem for the conventional Time-Spectral approach, which expands the solution at every spatial node into a Fourier series spanning the period of motion. The proposed extension to the Time-Spectral method treats unblanked nodes in the conventional manner but expands the solution at dynamically blanked nodes in a basis of barycentric rational polynomials spanning partitions of contiguously defined temporal intervals. Rational polynomials avoid Runge's phenomenon on the equidistant time samples of these sub-periodic intervals. Fourier-and rational polynomial-based di↵erenti-ation operators are used in tandem to provide a consistent hybrid Time-Spectral overset scheme capable of handling relative motion. The hybrid scheme is tested with a linear model problem and implemented within NASA's OVERFLOW Reynolds-averaged NavierStokes (RANS) solver. The hybrid Time-Spectral solver is then applied to inviscid and turbulent RANS cases of plunging and pitching airfoils and compared to time-accurate and experimental data. A limiter was applied in the turbulent case to avoid undershoots in the undamped turbulent eddy viscosity while maintaining accuracy. The hybrid scheme matches the performance of the conventional Time-Spectral method and converges to the time-accurate results with increased temporal resolution.

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